Chapter 21: Acquired Heart Disease

1. Although advances have been made in percutaneous coronary intervention techniques for coronary artery disease, survival is superior with coronary artery bypass grafting in patients with left main disease, multivessel disease, and in diabetic patients.

2. Coronary artery bypass grafting has become increasingly safe, and improves late mortality in patients with left main or proximal left anterior descending disease, multivessel disease, and in patients with diabetes.

3. Despite the theoretical advantages, the superiority of off-pump coronary artery bypass to conventional coronary artery bypass grafting has not been clearly established and other factors likely dominate the overall outcome for either technique.

4. Although mechanical valves offer enhanced durability over tissue valve prosthesis, they require permanent systemic anticoagulation therapy to mitigate the risk of valve thrombosis and thromboembolic sequelae, and thus are associated with an increased risk of hemorrhagic complications.

5. Mitral valve repair is recommended over mitral valve replacement in the majority of patients with severe chronic mitral regurgitation. The decision to proceed with mitral valve repair is based on the skill and experience of the surgeon in performing repair, and on the location and type of mitral valve disease encountered at the time of operation.

6. Although open aortic valve replacement has traditionally been the only effective treatment in patients with severe calcific aortic stenosis, transcatheter aortic valve replacement is a developing technology that has proven beneficial for the treatment of aortic stenosis in seriously ill patients that had previously been deemed high risk or inoperable.

7. Mechanical circulatory support with newer generation continuous flow left ventricular assist devices has proven to be durable and effective both in bridging patients to transplant and as a means of “destination therapy” for patients who are not transplant candidates. Recent results for destination therapy have approached those of cardiac transplantation.

8. Performing a biatrial Cox-Maze lesion set results in freedom from atrial fibrillation in approximately 90% of patients and is superior to both catheter-ablation and more limited lesion sets for patients with persistent atrial fibrillation or enlarged left atria. Surgical ablation of atrial fibrillation is recommended for patients referred with concomitant valvular disease and those who have previously failed or are poor candidates for catheter-based approaches.

9. The preferred treatment for pericarditis depends on the underlying cause, although the disease typically follows a self-limited course and is best managed medically. Surgical pericardiectomy may have a role in treating relapsing pericarditis and, more commonly, chronic constrictive pericarditis.

10. Myxomas are the most common cardiac tumors, and, while benign, they should be promptly excised after diagnosis due to the risk of embolization, obstructive complications, and arrhythmias.

Clinical Evaluation

As with any other field in medicine, history, and physical examination form the foundation for the evaluation of a patient with acquired heart disease requiring surgical intervention. Obtaining a complete history will help identify comorbid conditions and assist in delineating the operative risks and prognosis after surgery. Physical examination not only reveals factors that may increase the complexity of surgery, such as previous surgery or peripheral or cerebral vascular disease. These may influence the operative approach but also help guide the choice and sequencing of diagnostic studies. A complete assessment of the patient allows the surgeon to make educated decisions regarding the optimal treatment strategy for the patient.

History

Symptoms suggestive of heart disease include: chest discomfort, fatigue, edema, dyspnea, palpitations, and syncope. Adequate definition of these symptoms calls for a detailed history-taking paying particular attention to onset, intensity, radiation, duration, and exacerbating/alleviating factors. The demands on the heart are determined by its loading conditions and metabolic state of the body, and symptoms are commonly accentuated with physical exertion or postural changes.

Angina pectoris is the hallmark of coronary artery disease (CAD), but may occur with other cardiac pathologies which results in ischemia from a mismatch between the supply of oxygen by the coronary circulation and the metabolic demand of the myocardium. Typically, angina is described as tightness, heaviness, or dull pain, most frequently substernal in location, lasting for a few minutes. This discomfort may radiate to the left arm, neck, mandible, or epigastrium. It is most often provoked by activities that increase metabolic demand on the heart such as exercise, eating, and states of intense emotion, and is typically alleviated by rest or use of nitroglycerin. It is important to note that a significant number of patients with myocardial ischemia, particularly diabetics, females, and the elderly, may have “silent” angina or angina equivalents (dyspnea, diaphoresis, nausea, or fatigue). The overlap of these features with those of noncardiac etiologies such as costochondritis, biliary colic, gastroesophageal reflux disease, diffuse esophageal spasm, and peptic ulcer disease, to name a few, can lead to misdiagnosis.

Heart failure can occur in the left and/or right heart and respective symptoms arise from congestion of blood flow owing to the inadequacies of the cardiac pump function. Left heart failure manifests as dyspnea, usually with exertion. Orthopnea suggests worsened pulmonary congestion with increased venous return and these patients are not able to lie flat. Ascites, peripheral edema, and hepatomegaly reflect congestion in the systemic venous circulation and are prominent features of right heart failure. Peripheral edema can occur in right heart failure secondary to systemic venous congestion, or in left heart failure due to salt and fluid retention due to impaired renal perfusion. Patients with chronic suboptimal perfusion and oxygenation can also have digital clubbing and cyanosis.

It is difficult to implicate cardiac disease based solely on the presence of fatigue as it is a very nonspecific symptom. However, most cardiac pathologies do result in fatigue or exercise intolerance of some degree. It is important to differentiate fatigue from exertional dyspnea which some patients may describe as “fatigue.”

Dyspnea is another common symptom seen in many heart diseases. Although generally a late symptom in patients with valvular heart disease or cardiomyopathy, it may be a relatively early complaint in some patients, particularly those with mitral stenosis. As stated previously, dyspnea is also an anginal equivalent and may signal a myocardial ischemic episode. Many primary pulmonary disorders feature dyspnea as their cardinal symptom and should be evaluated simultaneously as the physiology of the heart and lungs are intimately related, and can have dramatic influences on each other.

Patients typically describe palpitations as a “skipped beat” or “racing heart”. Depending on the clinical context, such as occasional premature atrial or ventricular beats in otherwise healthy individuals, these may be benign. Clinically significant arrhythmias, however, require thorough investigation. Atrial fibrillation is the most common arrhythmia and can occur alone or with concomitant cardiac pathologies. It results in an irregular, and at times, rapid heartbeat. Concurrent symptoms such as angina or lightheadedness/syncope are particularly worrisome for life threatening arrhythmias such as ventricular tachycardia or ventricular fibrillation, particularly in those with preexisting heart failure or ischemic heart disease.

Syncope associated with heart disease results from abrupt reduction of cerebral perfusion. Many of the potential etiologies are serious, including sinus node dysfunction, atrioventricular-conduction abnormalities, malignant arrhythmias, aortic stenosis, and hypertrophic obstructive cardiomyopathy. Any episode of syncope warrants a thorough evaluation and search for the root cause. ¹

In addition to a thorough inquiry regarding the above symptoms, it is important to obtain details about the patients’ medical/surgical history, family history, social habits (with regards to alcohol and tobacco use), current medications, and a focused review of systems, including an assessment of the patients’ functional status and frailty. Specific attention should be directed to the patients’ comorbidities which not only sheds light on the patients’ general health, but also helps delineate the risks if the patient were to undergo surgery. A strong family history of coronary artery disease, myocardial infarction, hypertension, or diabetes is of particular importance as they increase the individuals’ risks.

Functional Disability and Angina

With regard to heart failure, functional capacity is strongly correlated with mortality. The New York Heart Association (NYHA) functional classification is the most widely used classification system in categorizing patients based on their functional status (Table 21-1). The NYHA classification has become a basis by which to assess patient characteristics in many studies to compare patient populations. Although less commonly used, the Canadian Cardiovascular Society (CCS) angina classification is also used to incorporate anginal symptoms into the functional assessment for prognostic value (Table 21-2).

Physical Examination

The physical examination is an invaluable tool in directing further diagnostic studies and management of a patient with suspected heart disease. The astute clinician will detect subtle signs that may further characterize the underlying pathologic process.

The general appearance of a patient is important in the clinical assessment. A pale, diaphoretic, and obviously uncomfortable patient is more likely to be in a clinically critical condition than one who is conversing comfortably with an unremarkable demeanor. In addition to basic vital signs, particular attention should be directed to the patients’ mental status and skin (color, temperature, diaphoresis) as these may be reflective of the general adequacy of perfusion. Overall frailty and dementia have also been shown to be predictors of operative and late mortality.²

Palpation of the precordium may demonstrate deviations in the point of maximal impulse indicative of ventricular hypertrophy or parasternal heaves seen in right ventricular overload. Auscultation should be performed in a quiet environment as critical murmurs, rubs, or gallops may be subtle. Murmurs are characterized by their location, timing, quality, and radiation. They are typically secondary to valvular or other structural pathology and new findings require further investigation. A rub due to pericardial friction is specific and virtually pathognomonic for pericarditis. A third heart sound (S₃) is generated by the rapid filling of a stiff ventricle and can be normal in young patients, but when present in older adults, is indicative of diastolic dysfunction and is pathologic. Increased contribution of the atrial pump function to ventricular filling may manifest as a fourth heart sound (S₄) and is also suggestive of ventricular dysfunction.

Palpation of peripheral pulses is important not only to assess the adequacy of perfusion, but the burden of coronary artery disease often correlates with the degree of peripheral arterial disease. Discovery of carotid stenosis by auscultation for carotid bruits has significant implications for operative planning.

Heart disease will frequently have extracardiac manifestations and examination of the other organ systems should not be neglected. Auscultation of the lung fields may reveal rales in patients with pulmonary edema. The work of breathing may also be assessed simply by observing the patient. Jugular venous distention and hepatosplenomegaly are seen in right heart failure.

Cardiac Risk Assessment in General Surgery Patients

Approximately one half of the mortality in patients undergoing noncardiac surgery is due to complications which are cardiovascular in origin.³ The American College of Cardiology and American Heart Association have formed a joint task force to publish a consensus statement on guidelines and recommendations which was revised in 2007.⁴ The aim of these guidelines is to incorporate surgery-specific risks and patient characteristics to stratify patients in order to guide perioperative decision-making.

Surgical procedures have been categorized based on cardiovascular risk into low and moderate risk, and vascular procedures. Vascular procedures (aortic, peripheral vascular, and other major vascular surgery), likely due to both the nature of the procedures themselves as well as the associated cardiovascular pathology in many of these patients, carries the highest reported cardiac risk at more than 5%. Low risk procedures, including endoscopic procedures, superficial operations, cataract surgery, breast surgery, and ambulatory surgeries have a risk generally less than 1%. Intermediate risk procedures are: intraperitoneal and intrathoracic surgery, head and neck surgery, orthopedic procedures, and prostate surgery.

Patient characteristics can be classified by the status of the patients’ cardiac disease, comorbid conditions, and functional capacity. Patients are considered to be at major perioperative clinical risk if they have one or more of the following active cardiac conditions: unstable coronary syndrome, decompensated heart failure, significant arrhythmias, or severe valvular heart disease. In these patients, intensive evaluation and treatment prior to surgery (unless emergent) is warranted, even if the noncardiac surgery needs to be delayed or cancelled.

If the patient does not have any of the previously mentionedactive conditions, and is scheduled for a low risk surgery or if they have functional capacity greater than or equal to 4 metabolic equivalents (or METs), the official recommendation is to proceed with the planned operation. The previous guidelines contained intermediate and low cardiovascular risk profiles, but this has been replaced by cardiovascular risk factors in the update. These risk factors are: history of ischemic heart disease, history of prior or compensated heart failure, history of cerebrovascular disease, diabetes mellitus, and renal insufficiency. Based on the number of present risk factors and the surgery-specific risk, the guideline recommends pathways for further evaluation and risk management (Table 21-3).

Diagnostic Studies

Electrocardiogram and Chest X-ray

Electrocardiograms (ECGs) and chest X-rays are simple, noninvasive, and inexpensive diagnostic studies that are invaluable in the preoperative assessment of patients with cardiac pathology. ECGs can be useful in detecting old myocardial infarction, dilation or hypertrophy of cardiac chambers, arrhythmias, and conduction abnormalities. A stress ECG requires a patient to exercise to a target heart rate, and is used to help diagnose ischemic pathologies which may not be evident at rest.

A plain film of the chest can detect pulmonary pathology, sequelae of heart failure (e.g., pulmonary edema, cardiac enlargement, pleural effusions) as well as hardware from previous procedures such as, prosthetic valves, sternal wires, pacemakers, and defibrillators.

Echocardiography

Echocardiography utilizes reflected sound waves to image the heart, and is used widely due to its noninvasive nature and low cost. It is the primary diagnostic tool used to evaluate structural diseases of the heart, including: valvular pathology, septal defects, cardiomyopathies, and cardiac masses. Echocardiography is indispensable in assessing surgical prosthetics such as valves, leads, or mechanical circulatory support devices. These examinations can be performed with M-mode imaging (motion along a single line) as well as 2-D and 3-D imaging depending on the graphical information required.

Doppler technology has become a standard addition to assess changes in flow patterns across both stenotic and regurgitant valves. Velocity measurements can be obtained to estimate pressure gradients across structures using the continuity equation. A common example would be the estimation of pulmonary arterial systolic pressure calculated from the regurgitant tricuspid jet profile during right ventricular systole.

Transthoracic echocardiography (TTE) requires no sedation and is generally performed with the patient in a slight left lateral decubitus position. Standardized views are obtained with the ultrasound probe placed in the apical, parasternal, subcostal, and suprasternal positions. The apical four-chamber view is a useful window for visualizing all four cardiac chambers simultaneously as well as the tricuspid and mitral valves. Other windows can be obtained to assess specific structures such as the individual valve anatomy or myocardial wall segments. Dobutamine-stress echocardiography is a study similar in idea to the stress ECG which utilizes a pharmacologic agent to assess the patient for ischemia or stress-induced valvular abnormalities.

A slightly invasive variant of this technology is transesophageal echocardiography (TEE) which takes advantage of the anatomic proximity of the heart to the esophagus. The exam is performed using a special endoscope with an ultrasound probe mounted on its end which is introduced orally into the esophagus under sedation. Posterior structures such as the mitral valve and left atrium are particularly well visualized. TEEs are frequently used intraoperatively during cardiothoracic surgery to assess global cardiac function, integrity of valve repairs and replacements, intracavitary thrombus and/or air, and aortic atherosclerosis or dissections which can have significant influences on operative strategy.

There are some new additions to the echocardiographic armamentarium which capitalize on the strengths of ultrasound imaging. Three dimensional TEE is playing an increasing role in the preoperative and intraoperative evaluation of patients with valvular heart disease and is particularly useful in the valuation of mitral regurgitation. Tissue Doppler imaging is based on principles akin to conventional Doppler echocardiography, but attention is directed to the myocardium itself as opposed to the motion of blood to quantify abnormalities in wall motion. Strain imaging with speckle-tracking echocardiography measures the actual deformation of the myocardium by following inhomogeneities inherent to the myocardium, and is a useful measure of myocardial function.

Radionuclide Studies

Although ECGs are useful, inexpensive, and safe, baseline abnormalities in the ECG may limit its diagnostic capacity. In particular, ventricular rhythms, bundle-branch blocks, left ventricular hypertrophy, drug effects, and baseline ST-segment depressions can make stress ECGs uninterpretable. In this setting, myocardial perfusion imaging (MPI) using radionuclides can be utilized to assess myocardial ischemia.

Thallium 201 (²⁰¹Tl) was the initial radionuclide used for MPI, but due to its long half-life and relatively low photopeak, it has largely been replaced by Technetium-99m (sestamibi and tetrofosmin) which has more favorable characteristics. In the past, planar imaging with three separate two-dimensional views of the heart were obtained. Currently, it is more common to have the images acquired by single-photon emission computed tomography (SPECT) technology which detects emitted photons from 180- to 360-degrees around the patients. The signals are then processed to reconstruct multiple slices which together provide a three-dimensional view. The amount of uptake at both rest and stressed states are compared to assess ischemia and viability of the myocardium. The distribution of radionuclides depend on perfusion and therefore areas which show uptake at rest, but not during stress are concerning for ischemia.

Territories that do not show uptake at rest or during stress are likely to be nonviable scar. The sensitivity and specificity of exercise SPECT are 90% and 70%, respectively.⁵

The image acquisition may also be gated to a simultaneously obtained ECG to assess global ventricular function. The endocardial and epicardial borders (as delineated by radionuclide uptake) are detected throughout the cardiac cycle and the ejection fraction, along with end-systolic and end-diastolic volumes, can be calculated. This study is also useful in revealing hypokinetic segments of the myocardium.

One of the most significant weaknesses of SPECT imaging is that it shows regional ischemia well, but does not adequately detect global or “balanced” ischemia which can occur with diffuse CAD. Positron emission tomography (PET) scans have been used due to its ability to obtain absolute quantitative data on both myocardial perfusion and metabolism. Tracers used in PET scans can be divided into those that assess perfusion (Oxygen-15, Nitrogen-13, and Rubidiuim-82) and those that assess metabolism (Carbon-11 and Fluorine-18). The specificity of PET in detecting CAD is better than SPECT at 86% due to its superior spatial resolution.⁶

Magnetic Resonance Imaging

Magnetic resonance imaging (MRI) has a wide variety of uses in cardiac imaging depending on the pulse sequence and signal weighting. Cine-loop of the heart throughout the cardiac cycles can yield information on global chamber function and valvular pathologies. The differential response of normal and ischemic myocardium to certain pulse sequences allows imaging of myocardial perfusion using MRI. Use of contrast agents such as gadolinium can enhance scar tissue and are very useful in viability assessment. Myocardial strain imaging can also be performed using newer technologies taking advantage of radio-frequency tagging of the myocardium which deforms with the tissue and can be followed throughout the cardiac cycle.

Cardiac Catheterization

Cardiac catheterization involves access to the cardiac chambers and great vessels with a peripherally inserted catheter under fluoroscopic guidance. It is a versatile tool used for diagnostic purposes of: cardiac chamber pressures, valvular abnormalities, wall motion assessment, and coronary artery anatomy. While some of these roles are being replaced by less invasive techniques mentioned previously, cardiac catheterization studies continue to be widely performed and is the gold standard for the assessment of coronary artery disease.

A left-heart catheterization is performed by percutaneous access of the femoral, or less commonly, the radial artery. Under fluoroscopic guidance, the catheter is threaded into the aorta where a contrast aortogram may be performed. Coronary angiography requires manipulation of this catheter into the coronary ostia where contrast is directly injected. With advancement of the catheter retrograde past the aortic valve, left ventricular pressures can be obtained. This pressure is used to calculate pressure gradients across the aortic valve which becomes particularly important in the evaluation of aortic stenosis. Again, contrast injection will result in a ventriculogram used to estimate ejection fraction and visualize hypokinetic segments of the walls. Inappropriate retrograde leakage of contrast may indicate insufficiency of the aortic and/or mitral valves.

Right heart catheterization is performed through a peripheral vein and the catheter is threaded into the right atrium. Right-sided pressures and structures are assessed in a similar fashion as in the left heart. Extension of the catheter into the pulmonary artery allows measurement of the pulmonary artery pressures as well as the pulmonary capillary wedge pressure (reflecting left ventricular end diastolic pressure) with an occlusive balloon.

In addition to these measurements, cardiac output can be measured using thermodilution or by the Fick method using oxygen saturations of blood sampled from the various locations during the procedure.

Coronary angiography provides information on hemodynamically significant stenoses in the coronary circulation as well as an anatomical roadmap for surgeons to planning revascularization. (Fig. 21-1A & B) A stenosis is considered to be significant if it narrows the lumen of the artery by 70% (or 50% in the case of left main coronary artery). There is some variability in the coronary arterial anatomy with the posterior descending artery being supplied by the right coronary artery in approximately 80% of patients (right dominant), or the left coronary artery in approximately 15% of patients (left dominant). The remaining patients have a codominant circulation where the posterior descending artery is supplied by both the right and left coronaries.

An advantage of catheterization is that it offers an opportunity for interventional therapy of coronary artery disease, arrhythmias, valvular abnormalities, and other structural defects of the heart. Cardiac catheterization is generally safe, but being an invasive procedure, it is associated with complications. Overall mortality is 0.11%, and total rate of major complications, including: MI, stroke, arrhythmia, vascular injury, contrast reaction, hemodynamic instability, and cardiac perforation is usually <2%.⁷

Cardiac Computed Tomography

Multislice computed tomography (CT) imaging can be used to assess the coronary vasculature. The coronary calcium score is an index developed to quantify the degree of coronary atherosclerotic burden by measuring Hounsfield units in a noncontrast cardiac CT. Although this technique is quite sensitive for angiographic stenoses >50%, it remains fairly nonspecific as calcification often precedes significant luminal narrowing.⁸ CT coronary angiography using intravenous contrast is also utilized clinically to assess coronary pathology and is particularly useful in the emergency room to perform a “triple rule-out” for acute coronary events, pulmonary embolism, and aortic dissection in patients who present with undifferentiated chest pain. LV ejection fraction may be measured by this technique, and together with the degree of coronary stenoses, incremental prognostic value has been demonstrated in addition to routine clinical predictors.⁹

History

Prior to the development of extracorporeal perfusion, heart surgery was rarely performed and was limited to brief periods of asystole and hypothermia. The need for a bloodless operating field, while maintaining perfusion of heart and other organs, was evident.

John Gibbon’s motivation to develop a means for extracorporeal perfusion came from a desire to safely open the pulmonary artery in a patient who suffered from a pulmonary embolus following cholecystectomy. After numerous experimental iterations, Gibbon’s cardiopulmonary bypass machine was first used clinically in 1953 to repair a large atrial septal defect in an 18-year-old female.¹⁰

Although Gibbon is credited for its invention, the development of modern cardiopulmonary bypass (CPB) is a culmination of the work of many investigators throughout the world. The early bubble oxygenators have evolved into the modern membrane oxygenators. The search for an ideal biocompatible material which minimizes the inflammatory cascade initiated by the contact of blood with the circuit components continues to this day.

Technique

The basic CPB circuit consists of the venous cannulae, a venous reservoir, pump, oxygenator, filter, and the arterial cannula.

Anticoagulation is required during CPB, and 300 to 400 units/kg of heparin is given to increase the activated clotting time (ACT) to greater than 450 seconds. Once adequate anticoagulation is achieved, arterial cannulation is performed through a purse-string suture, or through a side graft which is sewn on to the native artery. The distal ascending aorta is the most common site of cannulation, but there may be concern for atheroembolization when the aorta is atherosclerotic. Other sites of cannulation include the femoral artery, axillary artery, or the distal aortic arch. Venous cannulation is performed through purse-string sutures placed on the right atrium either for a single cannula or for two separate cannulae extending into the superior and inferior vena cava, respectively. Alternatively, the venous cannula may be inserted from the femoral vein and advanced into the right atrium.

Effective communication between the surgeon, the anesthesiologist, and the perfusionist is mandatory for effective cardiopulmonary bypass. Once the appropriate cannulations and connections are complete, CPB is commenced. Venous return is initiated followed by arterial flow while monitoring systemic blood pressures. At normothermia, the flow required is approximately 2.4 L/min/m², but with hypothermia, oxygen consumption is reduced by 50% for every 10°C drop in temperature, and a flow of only 1L/min/m² is required at 18°C. Once the heart is decompressed and hemodynamics are acceptable, ventilation is stopped. The oxygenator is adjusted to maintain a PaO₂ of 150 mm Hg and normocarbia. Blood can also be filtered and returned through vents that are placed in the heart or through the cardiotomy suction used to aspirate blood from the surgical field.

When the cardiac procedure is complete, the patient is rewarmed, the lungs ventilated, and the heart defibrillated if needed. The venous return to the CPB machine is gradually reduced allowing the heart to fill. The pump is also slowed while hemodynamics and global cardiac function are assessed with a TEE probe. Inotropic and vasopressor support may be used to augment cardiac function and treat hypotension. Once CPB has been stopped and stable hemodynamics achieved, the cannulae are removed. The heparin anticoagulation is reversed with protamine and hemostasis is achieved.¹¹

Adverse Effects

Cardiopulmonary bypass has a number of deleterious effects as various intertwining processes result in derangements in hemostasis, systemic inflammatory response, and end-organ function.

Anticoagulation prior to the commencement of CPB is required as contact of blood with the artificial surfaces of the circuit can initiate a thrombogenic cascade. Generation of thrombin plays a major role in both thrombotic and bleeding phenomena during CPB. The endothelium which normally regulates the fine balance between procoagulant and anticoagulant pathways is perturbed. Fibrinogen is consumed rapidly as thrombin converts fibrinogen to fibrin while fibrinolytic mechanisms (initiated by the activated endothelium) degrade the fibrin macromolecules. Platelets are activated by the converging hemostatic pathways and are consumed.

The response of the humoral and cellular immune systems partly overlap with the hemostatic pathways. The classic and alternative complement pathways are activated by CPB generating powerful chemotaxic molecules and anaphylatoxins. Monocytes, platelets, and neutrophils are activated releasing acute inflammatory mediators and cytokines which persist even after conclusion of CPB.¹² These inflammatory cells also produce reactive oxidants which may have cytotoxic effects.

The large quantity of unfractionated heparin used during cardiac surgery predisposes patients to developing heparin induced thrombocytopenia (HIT) with an incidence of 1% to 2%. Platelet factor-4 (PF4) is produced by platelets and avidly binds to heparin to form a heparin-PF4 complex which can be antigenic in some patients binding IgG. The IgG-heparin-PF4 complex can bind to platelets which causes release of more PF4, perpetuating the process. The earliest sign is a sudden drop of more than 50% of the platelet count, and HIT can be confirmed with an ELISA or serotonin release assay. Of the patients with HIT, 20% to 50% of patients develop thromboses in arterial or venous beds, designated as heparin induced thrombocytopenia and thrombosis (HITT), which can be life-threatening.¹³

The etiology of end-organ dysfunction resulting from extracorporeal circulation can mostly be categorized into one of three mechanisms. Although cardiac output and blood pressure are monitored carefully during CPB, they are surrogates for regional perfusion and cannot detect end-organ hypoperfusion directly. This can be a problem particularly with the cerebral, renal, and mesenteric circulations. With manipulation of diseased vessels and dysregulation of the native coagulation system, macroscopic and microscopic emboli are a concern despite various strategies to minimize this problem. Activated cells and circulating cytotoxic products of the immune response may cause microvascular injury and edema of other organs manifesting as neurocognitive deficits, respiratory failure, and renal injury.¹⁴

Myocardial Protection

During CPB, pharmacologic agents in cardioplegic solutions may be delivered into the coronary circulation to arrest the heart allowing for a still operating target and improved myocardial protection. The most common cardioplegia consists of potassium-rich solutions that can be mixed with autologous blood and are delivered into the coronary circulation. Antegrade cardioplegia is delivered into the root of a cross-clamped aorta or directly into the individual coronary ostial via specialized catheters. A retrograde cardioplegia catheter is a balloon-cuffed catheter that is placed through the right atrium into the coronary sinus and is used to perfuse the coronary circulation in the opposite direction through the venous circulation. This has the advantage of more uniform distribution in patients with diffuse coronary artery disease and is not dependent on a competent aortic valve for delivery.

There are controversies regarding the method (antegrade retrograde vs. both), type (crystalloid vs. blood), temperature (cold vs. warm vs. tepid), and interval (continuous vs. intermittent) of cardioplegia delivery. The optimal combination is beyond the scope of this text. However, most surgeons in the United States favor cold blood potassium cardioplegia.

History

The Vineberg operation, one of the initial attempts at surgical revascularization of the myocardium, was first performed in 1950s. This procedure involved implantation of the internal thoracic artery directly into the myocardium itself. While some patients were relieved of their anginal symptoms, this resulted in very little increase in coronary flow and was supplanted by methods to restore flow directly. Coronary endarterectomy was introduced by Longmire during this time period, but was met with high rates of restenosis and occlusion. The use of vein patches to repair the arteriotomy sites was described by Senning in 1961. The first saphenous vein coronary artery bypass grafting (CABG) was performed by Sabiston in 1962, but was popularized by Favalaro in 1967. In 1968, the internal thoracic artery was introduced as a bypass conduit by Green who used it to bypass the left anterior descending coronary artery.¹⁵

Etiology and Pathogenesis

Atherosclerotic stenoses are the primary mechanism of coronary artery disease (CAD). The pathophysiologic process is initiated with vascular endothelial injury and is potentiated by inflammatory mechanisms, circulating lipids, toxins, and other vasoactive agents in the blood. Macrophages and platelets are attracted to this area of endothelial dysfunction inciting a local inflammatory response. During this process, macrophages infiltrate into the intimal layers and accumulate cholesterol-containing low-density lipoproteins. The growth factors secreted promote proliferation of smooth muscle cells within the intima and media of the arteries. Together with the accumulation of the lipid-laden macrophages, the smooth muscle hyperplasia results in an atheroma and subsequently stenosis of the vessel. These atheromas have a fibrous cap which may rupture, exposing the underlying cells and extracellular matrix which are very prothrombotic. Acute plaque rupture and thrombus formation is thought to be the main pathophysiologic mechanism responsible for acute coronary syndromes.^16,17,18

Risk Factors and Prevention

Prior to the establishment of modern management strategies, the annual mortality rated from ischemic heart disease was quoted to be around 4% by the Framingham study. Since then, risk factor modification along with use of medications, such as aspirin and β-blockers, has dramatically improved survival.

The major risk factors of atherosclerosis include: age, cigarette smoking, hypertension, dyslipidemias, sedentary lifestyles, obesity, and diabetes. Likely due to increased public awareness and aggressive medical management, these risk factors (with the exception of glucose intolerance and obesity) have recently been on the decline.

Current guidelines outlined in the AHA/ACC consensus statement summarizes secondary prevention recommendations. Class I recommendations are: smoking cessation and avoidance of environmental tobacco exposure, blood pressure control to under 140/90 mm Hg (under 130/80 mm Hg in those with diabetes or chronic kidney disease), LDL cholesterol levels less than 100 mg/dL, aspirin therapy in all patients without contraindications, BMI target of less than 25 kg/m2, diabetes management with target HbA1c <7%, and encouragement of daily aerobic exercise routines. Beta-blockers are to be considered in patients with LV dysfunction and following MI or ACS. Renin-angiogensin-aldosterone system blockade in patients with hypertension, LV dysfunction, diabetes, or chronic kidney disease should also be considered.¹⁹

Clinical Manifestations

Patients with CAD may have a spectrum of presentations, including angina pectoris, myocardial infarction, ischemic heart failure, arrhythmias, and sudden death.

Angina pectoris is the pain or discomfort caused by myocardial ischemia and is typically substernal and may radiate to the left upper extremity, left neck, or epigastrium. The variety of presentations can make myocardial ischemia difficult to diagnose. Characteristics of chest pain that make myocardial ischemia less likely include: pleuritic chest pain, pain reproducible by movement or palpation, or brief episodes lasting only seconds. Typical angina is relieved by rest and/or use of sublingual nitroglycerin. Differential diagnoses to be considered include, but are not limited to: musculoskeletal pain, pulmonary disorders, esophageal spasm, pericarditis, aortic dissection, gastroesophageal reflux, neuropathic pain, and anxiety.

Myocardial infarction is a serious consequence of CAD occurring when ischemia results in myocardial necrosis. This may be silent and need not be preceded by angina. Necrosis may result in disruption of the myocardial integrity leading to devastating conditions such as intracardiac shunts from ventricular septal defects, acute valvular regurgitation from rupture of necrotic papillary muscles, and cardiac aneurysms which have the catastrophic potential to rupture.

The ischemic insults from CAD may lead to congestive heart failure. The initial myocardial damage sets off a cascade of responses, both local and systemic. Over time, these changes can cause deleterious myocardial loading and abnormal neurohumoral responses that result in pathologic remodeling of the heart. Heart failure should be suspected in patients who present dyspnea, orthopnea, fatigue, and edema.

Arrhythmias may also be a sequela of CAD. Ischemic etiologies should be investigated in patients who present with new arrhythmias. CAD may result in arrhythmias following an acute MI or as the result of ultrastructural and electrophysiologic remodeling secondary to chronic ischemic heart disease. Ischemia of the electrical conduction system may be seen as the new onset complete or partial atrioventricular conduction blocks.

Preoperative Evaluation

A focused history and physical examination is essential with particular attention directed to the signs, symptoms, and clinical manifestations mentioned previously. The patient’s functional status is of importance not only because it is a component of preoperative risk assessment, but also because quality of life improvement and symptomatic relief are both goals of surgical therapy.

Coronary angiography is the primary diagnostic tool. The coronary anatomy and degrees of stenoses are delineated allowing for planning of surgical revascularization.

Noninvasive diagnostic studies, in combination with provocative maneuvers (exercise or pharmacologic agents) offer information regarding the functional significance of ischemic disease. A stress ECG is frequently used as a screening tool with a high sensitivity. The positive predict value is 90% in patients with ST-segment depression >1mm. This test however, requires patients to achieve a certain elevation in their heart rate, and is therefore not suitable for those that cannot achieve this goal. Furthermore, baseline ECG abnormalities may render it impossible to detect typical ischemic changes with stress.

Echocardiography and nuclear imaging may be performed under pharmacologic stress (with dobutamine or dipyridamole) to assess reversible ischemia and myocardial viability. Technetium-99m or thallium-201 perfusion scans have an average sensitivity and specificity of 90% and 75%, respectively. Stress echocardiography has a similar sensitivity and specificity of approximately 85%.²⁰ These studies also have the ability to assess global ventricular function in terms of LV ejection fraction which can be used to determine operative risk.

Indications

A joint committee established by the American College of Cardiology and the American Heart Association have published guidelines for surgical revascularization (CABG) in CAD. The indications, categorized by presentation and angiographic disease burden as well as by treatment intention (survival improvement and symptom relief), are summarized later (Tables 21-4,5,6).²¹

Percutaneous Coronary Intervention vs. Coronary Artery Bypass Grafting

In recent years, there have been multiple prospective randomized, controlled trials as well as retrospective studies looking at the comparative effectiveness of percutaneous coronary interventions (PCI) and CABG. Some of the representative studies are summarized here.

The New York State Study (2005)

A retrospective review of 59,314 patients in two of New York’s registry with multivessel (2 or more) coronary disease was performed. Of these, 37,212 patients received a CABG and the others underwent a PCI. After adjusting by means of proportional-hazards methods, CABG was associated with higher adjusted rates of long-term survival than PCI.²²

Stent or Surgery Trial (2008)

An international multicenter randomized controlled trial of 988 patients (n = 488 PCI, n = 500 CABG) with multivessel CAD was performed to compare revascularization strategies. At 2-year median follow-up, the PCI group had significantly higher rates of repeat revascularizations and mortality compared to the CABG group (incidence of nonfatal Q-wave myocardial infarctions were similar in both groups). The median follow-up was extended to 6-years, and a survival advantage persisted in the CABG group over the PCI group.²³

Synergy between Percutaneous Coronary Intervention with Taxus and Cardiac Surgery (SYNTAX Trial, 2009)

Revascularization strategies, CABG vs. PCI, were compared in a 1:1 randomized prospective trial of 1800 patients with high risk coronary artery disease (left-main or triple-vessel disease). Rates of requirement for repeat revascularization and major adverse cardiac or cerebrovascular events at 12-months were lower in the CABG patients (5.9% and 12.4%, respectively) compared to PCI patients (13.5% and 17.8%, respectively). No difference in mortality was seen between the groups at 12-months.²⁴

The ACCF and STS Database Collaboration on the Comparative Effectiveness of Revascularization Strategies (ASCERT Study, 2012)

This study, performed by collaboration of the American College of Cardiology Foundation and the Society of Thoracic Surgeons, reviewed their respective national databases of patients over the age of 65 who had multivessel coronary disease (excluding those with left main disease). CABG was performed on 86,244 patients and 103,549 underwent PCI. There was no difference in adjusted mortality at 1 year, but there was a significantly lower mortality with CABG than PCI at 4 years.²⁵

Summary

PCI technology has improved over time and rates of periprocedural adverse events have decreased significantly. Management strategies must be tailored to the individual patient’s clinical status and context, but CABG maintains improved long-term outcome and remains the standard of care for left-main and multivessel coronary artery disease.

Operative Techniques and Results

Bypass Conduit Selection

The most important criterion in conduit selection is graft patency. The conduit with the highest patency rate (98% at 5 years and 85%–90% at 10 years) is the internal thoracic artery which is most commonly left attached proximally to the subclavian artery (although occasionally used as a free graft) and anastomosed distally to the target coronary artery.^26,27 The use of both internal thoracic arteries has been shown to increase event-free survival in a number of studies.^28,29

The greater saphenous vein can be harvested using an open or endoscopic technique. In the open technique, the initial incision is made along the course of the vein on the medial aspect of the lower extremity. The vein is harvested with meticulous attention directed towards minimizing manipulation of the vein itself. The incision may be continuous or bridged in an attempt to decrease the size of the incision, but multiple bridged incisions may have the potential risk of increased conduit manipulation during harvest. Endoscopic harvest is performed by making a small incision just above and medial to the knee where the endoscope is inserted. Side branches are cauterized under endoscopic visualization using bipolar electrocautery until dissection is carried proximally until the required length of vein is mobilized. A proximal counterincision is then made to extract the venous conduit which is prepared in the standard fashion.

The radial artery is another frequently used conduit. After confirmation of ulnar collateral flow to the hand by the clinical Allen’s test or a duplex ultrasound study, an incision is made from a point just proximal to the radial styloid process ending just medial and distal to the biceps tendon on the nondominant hand. With lateral retraction of the brachioradialis muscle, the radial artery is dissected sharply with care to avoid injury to the cutaneous nerves in this area and minimize manipulation of the artery itself. This artery can also be harvested using an endoscopic technique.

Many studies have looked at the patency rates of the radial artery graft in comparison to the saphenous vein graft. Although some studies have resulted in equivocal data, general consensus favors the use of radial arterial grafts over vein grafts with 5 year patency rates of 98% and 86%, respectively.^30,31

From a historical perspective, the anterior circulation (left main or left anterior descending artery) is generally bypassed using the internal thoracic artery and the lateral (circumflex artery) or inferior (right coronary artery) territories are bypassed using a saphenous vein or radial artery graft. These conduits may be combined to form a composite T- or Y-graft, or sewn to multiple targets as sequential grafts. Since patency is best with arterial grafts, recent data havesuggested that the best long term results are achieved with multiple or all-arterial revascularization, particularly in patients >70 years of age.^32,33 Other conduits such as the gastroepiploic arteries, lesser saphenous veins, and cephalic veins have been described, but are not widely used and will not be discussed here.

Conventional Coronary Artery Bypass Grafting

Traditionally, CABGs are performed with the patient lying supine through a median sternotomy. After the patient is heparinized, cardiopulmonary bypass is initiated. The aorta is cross-clamped and cardioplegia is delivered. Once adequate myocardial protection has been achieved, coronary arteriotomies are made and distal anastomoses are performed using Prolene suture. (Fig. 21-2A & B) The proximal anastomoses are then performed directly onto the ascending aorta or onto preexisting grafts. It is important to note that significant coronary stenoses can cause differential distribution of cardioplegia and myocardial protection. It is therefore recommended to use retrograde cardioplegia or to revascularize the area with the most concern for ischemia first, and give cardioplegia down the completed graft. The left internal thoracic artery to left anterior descending (LAD) graft is frequently performed last to avoid kinking or disruption of this important bypass. Once all grafts are in place, the patient is weaned from bypass. During this time, the heart is monitored closely by direct visual inspection, and transesophageal echocardiography to detect abnormalities which may signify inadequate revascularization or technical problems with the bypasses. Upon confirmation of hemostasis, chest tubes are placed, the sternum is approximated with sternal wires, and the incisions are closed.

Conventional CABG Results

Several early randomized trials have shown improved survival in patients who receive a CABG as opposed to medical therapy.^34,35,36 A propensity-matched study identified that CABG greatly benefited patients with LV dysfunction and left main stenosis >50% compared to medical management.³⁷ The Bypass Angioplasty Revascularization Investigation (BARI) trial demonstrated impressively superior results with CABG compared to PCI in terms of 5-year cardiac mortality (5.8% vs. 20.6%) in patients with diabetes in addition to CAD.³⁸ In a study examining the benefits of CABG over medical management for specific CAD distributions, survival was better in patients with proximal LAD stenoses, regardless of the number of diseased vessels.³⁹ In general, these studies show survival rates of over 90% at 5 years and approximately 75% at 10 years following CABG.

The mortality and morbidity of the procedure itself has changed over time. Data from the Society of Thoracic Surgeons (STS) database accounts for 1,497,254 patients who underwent a solitary CABG from 2000 to 2009. The mortality rate of CABGs have improved significantly from 2.4% in 2000 to 1.9% in 2009 despite the relatively constant predicted mortality rate of around 2.3%. In parallel with this, postoperative complication rates have decreased as: stroke (1.6%–1.2%), bleeding requiring reoperation (2.4%–2.2%), and deep sternal wound infection (0.59%–0.37%).⁴⁰

There are marked improvements in the functional status of patients receiving CABG. Patients’ 6-minute walk test distances were significantly increased 2 years postoperatively compared to their preoperative assessment.⁴¹ After 10 years, 54% of patients were free of chest pain and 31% were free of dyspnea.⁴²

Off-pump Coronary Artery Bypass

To avoid the adverse consequences of cardiopulmonary bypass, off-pump coronary artery bypass (OPCAB) was developed and has been adopted in some centers over the past two decades.

With OPCAB the heart is left beating. Performing anastomoses on the beating heart requires the use of myocardial stabilization devices which help portions of the epicardial surface to remain relatively immobile while the anastomoses are being performed. (Fig. 21-3) Carbon dioxide blower-misters are also used to clear blood from the operative site and improve visualization.

Apical suction devices are used to aid in exposure, particularly of the lateral and inferior vessels. Many creative maneuvers have been developed, including patient repositioning, opening the right pleural space to allow for cardiac displacement, and creation of a pericardial cradle to minimize compromise of cardiac function while exposing the various surfaces of the heart. Temporary proximal occlusion of the coronary artery being grafted is necessary to provide a bloodless target. This occlusion causes temporary ischemia, and if not tolerated, coronary shunts can be employed.

OPCAB Results

The superiority of OPCAB over on-pump CABG remains a controversy despite the large body of literature on this topic. A pooled analysis of two randomized trials, the Beating Heart Against Cardioplegic Arrest Studies (BHACAS 1 & 2), is one of several studies that have touted lower short term mortality rates with the off-pump compared to the on-pump technique.^43,44,45 Other studies, however, have demonstrated equivocal or contrary results.^46,47 Furthermore, the recent prospective and much larger ROOBY (Randomized On/Off Bypass) trial showed increased rates of adverse cardiac events with OPCAB compared to conventional CABG.⁴⁸ Despite the initial enthusiasm for the theoretical advantages of avoiding cardiopulmonary bypass, consistent benefits in clinical outcome have not been observed. There does seem to be a more or less uniform trend towards decreased perioperative blood product transfusions with OPCAB compared to on-pump CABG. In terms of other measures of early outcome, postoperative renal failure, stroke, and acute MI, the superiority of OPCAB has been unclear.^47,49,50

There have been questions whether the technical challenge of sewing on a beating heart leads to increased rates of graft occlusion following an OPCAB. The higher cardiac morbidity in the ROOBY trial was associated with decreased 1-year angiographic patency rates.⁴⁸ However, studies with contrasting findings exist, quoting equivalent rates of graft patency for OPCAB usage.^51,52 The broad variety in results may be suggestive that other factors (e.g.,surgeon skill, technical difficulty, patient factors) may be dominating the outcome rather than the use or avoidance of cardiopulmonary bypass.⁵³ After almost two decades, OPCAB has not been widely adopted and remains less than 2% of all CABG procedures in the United States.

Minimally Invasive Direct Coronary Artery Bypass

As an extension of the off-pump coronary revascularization technique, minimally invasive direct coronary artery bypass (MIDCAB) has been described. MIDCAB is performed using a left anterior mini-thoracotomy through which mobilization of the left internal thoracic and direct in situ anastomosis to the leftanterior descending artery (or its diagonal branches) is performed. This technique is primarily applicable to single-vessel disease, although reports of multivessel revascularizations do exist.

MIDCAB Results

A review of 411 patients undergoing MIDCAB quotes an operative mortality >1%. In this study, all patients received revascularization of the LAD only, regardless of the number of diseased vessels. The 3-year mortality in patients with single-vessel disease following a MIDCAB was 3.1%, which was, not surprisingly, lower than those with multivessel disease (8.7%).⁵⁴

There is an inherent selection bias in retrospective reviews comparing MIDCAB to OPCAB or conventional CABG as MIDCAB patients tend to have less extensive disease. Because of this, there have been multiple randomized controlled trials looking at the efficacy of MIDCAB compared to PCI. A meta-analysis of 5 randomized prospective trials comparing PCI to MIDCAB revascularization of isolated proximal left anterior descending artery demonstrated comparable results in terms of mortality, MI, and repeat revascularization requirement. It is worth noting however, that only one of these trials used drug-eluting stents (DES) in the PCI arm.⁵⁵ Hong et al showed similar efficacy with MIDCAB and DES PCI, and when this study was excluded from the meta-analysis, superiority of MIDCAB to PCI in regards to mortality, MI, and repeat revascularizations was seen.⁵⁶ Although no further prospective trials have been performed to compare DES PCI and MIDCAB in this patient cohort, a retrospective review of 186 patients has demonstrated significantly higher rates of angina recurrence and major adverse cardiac events in the DES PCI group.⁵⁷

Total Endoscopic Coronary Artery Bypass

With the advent of robotic surgical technology allowing stereoscopic visualization and increased instrument dexterity, total endoscopic coronary artery bypass (TECAB) has become possible. In July of 2004, the da Vinci robotic surgical system received FDA approval for use in coronary anastomoses. Extracorporeal circulation with peripheral cannulation has been used in earlier reports, but the development of mechanical stabilizers has provided the ability to perform the internal thoracic artery harvest and coronary anastomosis off-pump with use of the robotic arms only. Several studies have looked at the feasibility of TECAB, and have shown acceptable results, but this procedure has not been adopted by most surgeons due to its steep learning curve, longer operative times, and lack of demonstrable clinical benefit.^58,59,60

Hybrid Coronary Revascularization

With the continually increasing collaboration between cardiothoracic surgeons and interventional cardiologists, hybrid coronary revascularization (HCR) combining a minimally invasive surgical technique (MIDCAB or TECAB) with PCI has become a reality. This capitalizes on a major advantage of both treatments, utilizing the durable left internal thoracic artery to left anterior descending coronary artery bypass while treating other stenoses with PCI obviating the need for a large surgical incision or cardiopulmonary bypass. HCR is not without its downsides as there are some concerns with this approach since aggressive anti-platelet therapy is required with PCI and may increase the hemorrhagic complications of surgical revascularization. A small study comparing HCR to OPCAB showed comparable graft patency and decreased hospital stay with HCR without an increase in complication rates.⁶¹ There are, however, some studies that have reported increased rates of requirement for re-intervention in patients undergoing HCR, and this aspect requires further study.^62,63 These procedures have not gained widespread acceptance and their clinical value remains a matter of debate.

Transmyocardial Laser Revascularization

Despite the advancement of technology and revascularization strategies, patients with end-stage coronary artery disease may not be amenable to complete revascularization. Transmyocardial laser revascularization (TMR) relies on a CO₂ or holmium:yttrium-aluminum-garnet (Ho:YAG) laser to create multiple transmural channels (1mm in diameter) through the myocardium. The initial concept was that these channels would serve as conduits for direct perfusion from the ventricle, but evidence suggests that the resultant angiogenesis is primarily responsible for the improved perfusion. A meta-analysis of seven randomized controlled trials comparing TMR to medical therapy for chronic angina have shown higher rates of angina improvement in the TMR but was not able to show a difference in mortality between the two groups.⁶⁴

TMR is also being used as an adjunct to CABG in the treatment of extensive CAD that is not amenable to surgical revascularization alone. In a study looking at the benefits of TMR in addition to CABG, Allen et al concluded that TMR decreases angina burden when added to CABG in patients who cannot be revascularized by CABG alone.⁶⁵ The current STS guidelines support the consideration of TMR in patients with ischemic myocardial territories that cannot be revascularized by PCI or CABG.⁶⁶ Because of equivocal late results at most centers, this therapeutic strategy has not gained widespread acceptance.

New Developments

Regenerative Medicine and Tissue Engineering

Provocative investigations are being performed on the level of signaling molecules, gene therapy, stem cells, and tissue engineering to regenerate or replace damaged tissue in patients with ischemic heart disease. Growth factors, such as FGF and VEGF, are receiving focused attention due their ability to induce ingrowth of new vessels. Although concerns regarding systemic administration of these pleiotropic signaling molecules exist, early placebo-controlled clinical trials have shown some promising results with administration of these agents.^67,68 Adenoviral transfection of diseased tissue with transgenes for these same growth factors has also been attempted with variable results.

Research in tissue engineering has been directed at creation of vascular conduits that are resistant to atherosclerosis. Stem cells have also been infused directly into the site of injury or in the generation of new tissue around a biodegradable scaffold. Despite their potential, these technologies are still in their infancy and significant progress will be needed before more widespread clinical adoption.

General Principles

The number of patients referred for the surgical management of valvular heart disease has increased substantially in recent years, with the percentage of isolated valve procedures performed in the United States increasing from 14% of all cardiac operations in 1996, to 22% in 2006.⁶⁹ In 2012, valve proceduresrepresented over 50% of the cases performed at our institution. Although congenital and inherited etiologies represent important clinical entities, age-associated and acquired conditions still represent the primary causes of valvular heart disease, and are the focus of this section.

The most common screening method for valvular heart disease is cardiac auscultation, with murmurs classified based primarily on their timing in the cardiac cycle, but also on their configuration, location and radiation, pitch, intensity and duration (Table 21-7).⁷⁰ Although some systolic murmurs are related to normal physiologic increases in blood flow, some may indicate cardiac disease, such as valvular aortic stenosis (AS), that are important to diagnose, even when asymptomatic. Diastolic and continuous murmurs, on the other hand, are frequently pathologic in nature. Dynamic cardiac auscultation provides further evidence as to the significance and origin of many murmurs (Table 21-8).⁷⁰

Although auscultation may provide initial evidence to the existence of valvular disease, associated signs and symptoms may help narrow the diagnosis. Abnormalities in the splitting of the heart sounds and additional heart sounds should be noted, as should the presence of pulmonary rales. Peripheral pulses should be checked for abnormal intensity or timing, and the presence of a jugular venous wave should be documented. Additionally, symptoms of syncope, angina pectoris, heart failure, and peripheral thromboembolism are important and may help guide diagnosis and management.

Several imaging examinations are also available to aid in the diagnosis and classification of various valvular disorders. Electrocardiograms (EKGs) are widely available, and may provide information regarding ventricular hypertrophy, atrial enlargement, arrhythmias, conduction abnormalities, prior myocardial infarction, and evidence of active ischemia that would prompt further workup. Posteroanterior and lateral chest X-rays are also easy to obtain, and may yield information regarding cardiac chamber size, pulmonary blood flow, pulmonary and systemic venous pressure, and cardiac calcifications. The gold standard for the evaluation of valvular heart disease is transthoracic echocardiography (TTE).

Although helpful in the noninvasive evaluation of valve morphology and function, chamber size, wall thickness, ventricular function, pulmonary and hepatic vein flow, and pulmonary artery pressures, TTE may be unnecessary for some patients with asymptomatic cardiac murmurs. Current recommendations for evaluation via TTE are listed in Table 21-9.⁷⁰ Specialized examinations based on the specific findings of TTE examinations are discussed as appropriate in the following sections.

Regardless of the etiology, valvular heart disease can produce a myriad of hemodynamic derangements. Left untreated, valvular stenosis and insufficiency can produce significant pressure and volume overload on the affected cardiac chamber, respectively, with mixed disease consequently causing mixed pathology. Although the heart can initially compensate for alterations in cardiac physiology, cardiac function eventually deteriorates, leading to heart failure, decreasing patient functional status, ventricular dysfunction, and eventually death. In order to optimize long-term survival, surgery is recommended in various forms of valvular heart disease, and in an increasing number of elderly and high-risk patients.

Surgical Options

Although valve repair is increasingly indicated, especially in patients with aortic, mitral or tricuspid insufficiency, valve replacement may be necessary in certain patient populations. In some cases valve replacement can be accomplished with either mechanical or biological prostheses, and the choice of valve depends on many patient-specific factors such as age, health status, and desire for future pregnancy. Preexisting indications or contraindications to anticoagulation therapy also influence the choice of mechanical vs. tissue valve prosthesis.

Current options for mechanical valve replacement include tilting disc valves and bileaflet valves. Although mechanical valves are highly durable, they require permanent anticoagulation therapy to mitigate the otherwise high risk of valve thrombosis and thromboembolic sequelae.⁷¹ Due to the concordant risk of hemorrhagic complications, patient characteristics such as debility, lifestyle, and contraindications to systemic anticoagulation therapy may preclude mechanical valve replacement. Moreover, young women who are planning future pregnancies cannot take warfarin due to its teratogenic potential. Conversely, patients with other indications for systemic anticoagulation, such as other risk factors for thromboembolism (i.e., atrial fibrillation), or the existence of a mechanical prosthetic valve already in place in another position, may benefit from mechanical valve replacement. Additionally, patients with renal failure, on hemodialysis, or with hypercalcemia experience accelerated degeneration of bioprosthetic valves, and are thus, recommended to receive mechanical prostheses.⁷² In general, mechanical valve replacement is preferred in patients with expected long life spans who are acceptable candidates for anticoagulation therapy, in order to minimize reoperation and bleeding risks.

The potential to avoid the hazards of serious bleeding complications spurred the development of valve prostheses using biological materials, which obviate the need for systemic anticoagulation therapy. As tissue valves are naturally less thrombogenic, the attendant yearly risks of both thromboembolic and anticoagulation-related complications are considerably less than with mechanical valves.⁷³ Consequently, tissue valve replacement is generally recommended for patients averse to systemic anticoagulation therapy, with potential concerns regarding compliance or follow-up while taking anticoagulant medications, and in the case of reoperation for a thrombosed mechanical valve. However, biological valves are more prone to degeneration, especially when implanted in the mitral position, in younger patients, and in patients in renal failure, on hemodialysis, or with hypercalcemia.⁷³ Improved manufacturing methods have made currently available tissue valves more durable than previous versions, and valve replacement with a biological prosthesis is generally preferred in patients without other indications for anticoagulation therapy, who are >60 years of age for the aortic position, and >70 years of age for the mitral position.

Mechanical Valves

The first bileaflet valve was introduced in 1977. Bileaflet valves are comprised of two semicircular leaflets which open and close, creating one central and two peripheral orifices (Fig. 21-4). Bileaflet mechanical valves have demonstrated excellent flow characteristics, low risks of late valve-related complications, including valve failure, and are currently the most commonly implanted type of mechanical valve prosthesis in the world.⁷²

Although mechanical valves necessitate systemic anticoagulation, careful monitoring of the International Normalized Ratio (INR) reduces the risk of thromboembolic events and hemorrhagic complications, and improves overall survival.⁷⁴ Patients undergoing mechanical aortic valve replacement generally have a target INR of 2 to 3 times normal. Patients undergoing mechanical mitral valve replacement frequently have increased left atrial size, concomitant atrial fibrillation, and are at higher risk for thromboembolism that those undergoing mechanical aortic valve replacement, and are thus recommended to have a target INR 2.5 to 3.5 times normal. When managed appropriately, the yearly thromboembolic and bleeding risks in these patients are 1% to 2%, and 0.5% to 2%, respectively.

Tissue Valves

A xenograft valve is one implanted from another species, such as porcine xenograft valves, or manufactured from tissue such as bovine pericardium. A variety of xenograft tissue valves exist, and are primarily differentiated by the presence or absence of a mounting stent. Stented valves are the most commonly implanted, and the most popular valve in the United States is a stented bovine pericardial valve.

The more traditional stented valves are attached to a sewing ring, which decreases the technical complexity of valve replacement compared with stentless valves (Fig. 21-5). The chief disadvantage of stented tissue valves is a smaller effective orifice area, which increases the transvalvular gradient. This effect is most pronounced in patients with small prosthetic valve areas, specifically <0.85cm² valve area per square meter body surface area, and may affect symptomatic improvement and the hemodynamic response to exercise following surgery.⁷⁵

Stentless porcine xenograft valves were developed in order to minimize the limitations in flow characteristics seen in patients with small prosthetic valve areas, and have demonstrated an increase in effective valve area of approximately 10% over stented xenografts of equivalent size.⁷² They can result in improved hemodynamics, both at rest and with exercise.⁷⁶ The absence of a stent and sewing ring both increases the technical complexity of valve replacement, and takes advantage of the biologic mobility of the aortic valve apparatus. Though results with stentless valves seem promising, long-term durability remains to be shown, and they have not been widely adopted due to the technical complexity associated with implantation.

Homografts

Homograft valves from human cadavers, also known as allografts, have been used for aortic valve replacement since the technique was originally described over 50 years ago.⁷⁷ Since that time, homografts have typically been used for aortic and pulmonary valve replacements, and have been successfully harvested from brain dead organ donors and the explanted hearts of heart transplant patients. Following harvest, these valves are sterilized using an antibiotic solution, and subsequently stored in fixative or cryopreserved.

Like other types of tissue valves, the risk of thromboembolic complications with homograft valves is low, and systemic anticoagulation therapy is not required. Additionally, the structure of homograft valves is naturally low-profile, allowing for larger effective valve orifices and lower postoperative transvalvular gradients compared with stented xenograft valves. Additionally, they have been shown to have some advantages in patients with endocarditis.⁷⁸

The major shortcoming of homograft valves is their uncertain long-term durability in the face of significant tissue degeneration. Within one year of implantation, these valves undergo substantial loss of cellular components and subsequent structural compromise, which may ultimately lead to valve failure.⁷⁹ Although enhanced preservation techniques significantly improve cellular viability, which approach the 15-year viability of xenograft valves, the availability of these techniques has limited the use of homograft tissue valves.

Autografts

In 1967, Donald Ross described a procedure in which the diseased aortic valve is replaced using the patient’s native pulmonary valve as an autograft, which is in turn replaced with a homograft in the pulmonic position.⁸⁰ The procedure results in minimal transvalvular gradients, and favorable left ventricular mechanics, both at rest and during exercise. Known as the Ross procedure, this operation is particularly beneficial in children, as the pulmonary trunk grows with the child and long-term anticoagulation is not required.⁸¹

The late results of the Ross procedure are discussed later in this chapter. In addition to potential concerns with durability, performance of the Ross procedure has also been limited by its technical complexity, and the increased surgical risk associated with double valve replacement.

Valve Repair

Valve repair offers several advantages over valve replacement, due in large part to the preservation of the patient’s native valve and subvalvular apparatus. In the case of mitral valve (MV) surgery, preservation of the mitral apparatus has been shown to lead to better postoperative left ventricular function and survival.^82,83 Additionally, as there is no implanted prosthesis, the patient avoids the risks of chronic anticoagulation, infection, thromboembolic complications, and prosthetic valve failure after surgery.

In the case of MV repair, freedom from reoperation and valve-related complications has been excellent in certain patient populations, even at 20-year follow-up.⁸⁴ It has also been demonstrated that patients undergoing MV surgery with moderate functional tricuspid regurgitation (TR) do not experience increased perioperative complication rates when a concomitant tricuspid valve (TV) repair is performed.⁸⁵ Midterm results in this group are encouraging, with greater than 98% freedom from reoperation reported by some groups at 5 years, suggesting further indications for valve repair.

Despite its advantages for the patient, valve repair is generally more technically demanding than valve replacement, and may occasionally fail. Both the suitability of the patient for valve repair and the skill and expertise of the surgeon performing the operation are important when considering valve repair in the individual patient.

Mitral Stenosis

Etiology

Acquired mitral stenosis (MS) is most often caused by rheumatic fever, with approximately 60% of patients with pure MS presenting with a positive clinical history of rheumatic heart disease.⁷⁰ Rarely, other conditions can cause obstruction to filling of the left ventricle (LV), mimicking MS. Acquired causes of MV obstruction include left atrial myxoma, ball valve thrombus, mucopolysaccharidosis, previous chest radiation, and severe annular calcification.

Pathology

Although rheumatic heart disease is associated with a transmural pancarditis, pathological fibrosis of the valves results primarily from the endocarditic process. The damage caused by endocardial inflammation and fibrosis is progressive, causing commissural fusion, subvalvular shortening of the chordae tendineae, and calcification of the valve and subvalvular apparatus.⁸⁶ The resulting stenotic MV has a funnel-shaped apparatus, with a significantly narrowed orifice obliterated by interchordal and commissural fusion (Fig. 21-6). The degree of mitral stenosis should be determined preoperatively, as these pathological features may help determine the timing and type of intervention to perform.⁷⁰

Pathophysiology

As the normal MV area of 4.0 to 5.0 cm² is reduced by the rheumatic process, blood can flow from the left atrium to the left ventricle only if it is propelled by an ever-increasing pressure gradient. The diastolic transmitral gradient, which is a function of the square of the transvalvular flow rate and the diastolic filling period, is a fundamental expression of the severity of MS. When the valve area is reduced to <2.5 cm², patients may begin to experience symptoms when the transmitral gradient is exacerbated by conditions that either increase transmitral flow or decrease diastolic filling time, such as exercise, emotional stress, infection, pregnancy, or atrial fibrillation with a rapid ventricular response.⁸⁷ Symptoms may begin to occur at rest with the onset of moderate stenosis, defined as a cross-sectional area of 1.0 to 1.5 cm², and any physical exertion is typically limited by the time the MV area is <0.8 to 1.0 cm² (Table 21-10).⁷⁰

The progression of symptoms is due to the evolution of pathophysiological processes, beginning with an elevation in left atrial pressure. The increased left atrial pressure is subsequently transmitted to the pulmonary venous system, causing pulmonary edema as the hydrostatic pressure in the vessels exceeds the plasma oncotic pressure. Decreased pulmonary venous compliance exacerbates the pulmonary venous hypertension, though a concomitant decrease in microvascular permeability may preclude pulmonary edema in the chronic setting.⁸⁸ Patients may also develop pulmonary arterial hypertension, owing to vasoconstriction, intimal hyperplasia, and medial hypertrophy of the pulmonary arterioles in response to the increased pulmonary venous pressure. The secondary obstruction to flow caused by reactive pulmonary arterial hypertension may serve to protect against pulmonary edema, but also exacerbates the intractable decrease in cardiac output that develops as stenosis worsens.⁸⁹

Throughout the process, the left atrium becomes dilated and hypertrophied due to increased work in filling the ventricle against a fixed obstruction. Atrial fibrillation may develop, exacerbating the patient’s symptoms and increasing the risk of atrial thrombus and subsequent embolization. Left ventricular structure and function are typically preserved, however, owing to the protective effect of the stenotic valve.

Clinical Manifestations

The sudden opening of the thickened, nonpliable valve with left atrial contraction produces an opening snap, followed by a diastolic rumble caused by rapid entry of blood into the left ventricle. When diastole is complete, the MV subsequently closes very rapidly, causing an increased first heart sound. The murmur, classically known as the auscultatory triad, is best heard at the apex. Associated mitral and tricuspid insufficiencies are heard as a pansystolic murmur radiating to the axilla, and a systolic murmur at the xiphoid process, respectively.

The first clinical signs of MS are those associated with pulmonary venous congestion, namely exertional dyspnea, decreased exercise capacity, orthopnea, and paroxysmal nocturnal dyspnea. Hemoptysis, and pulmonary edema may develop as the venous hypertension worsens. Advanced MS can also cause pulmonary arterial hypertension and subsequent right heart failure, manifested as jugular venous distention, hepatomegaly, ascites, and lower extremity edema.¹

As mentioned previously, atrial fibrillation may develop as left atrial pathology worsens, causing atrial stasis and subsequent thromboembolism. Patients with MS may initially present with signs of arterial embolization, even rarely with angina from coronary occlusion.¹

Diagnostic Studies

All patients with a clinical history and physical exam suggestive of MS should undergo EKG and chest X-ray. Abnormalities in the EKG may include atrial fibrillation, left atrial enlargement, or right-axis deviation. Chest X-ray findings may include enlargement of the left atrium and pulmonary artery, creating a double contour behind the right atrial shadow, and obliterating the normal concavity between the aorta and left ventricle. Findings consistent with pulmonary congestion may also be present.¹

The diagnostic tool of choice is TTE, which not only confirms the diagnosis of MS, but also rules out other causes of stenosis and other concomitant myocardial or valvular heart disease.⁹⁰ Two-dimensional TTE can be used to calculate the MV orifice area and to determine the morphology of the MV apparatus, including leaflet mobility and flexibility, leaflet thickness and calcification, subvalvular fusion, and the appearance of the commissures. Doppler TTE can also be used in combination with various equations to estimate the hemodynamic severity of MS in terms of the mean transmitral gradient, the MV area, and the pulmonary artery systolic pressure.

In most cases further examinations are not necessary. A preoperative TEE is usually unnecessary, unless there is a need to rule out left atrial appendage thrombus, the patient is being considered for percutaneous mitral balloon valvotomy, or the preoperative TTE is insufficient for diagnosis. Exercise TTE is indicated when resting TTE parameters are discordant with symptom severity.⁹¹ Routine cardiac angiography should be performed prior to valve surgery in patients with evidence of ischemia, decreased LV systolic function, a history of coronary artery disease or coronary risk factors, including postmenopausal status and age ≥35 in men and premenopausal women.⁷⁰

Indications for Operation

Depending on the severity and the morphology of the diseased MV (Table 21-10), balloon valvuloplasty, surgical commissurotomy or repair, or MV replacement may be indicated for the treatment of MS (Table 21-11).⁷⁰

Mitral Regurgitation

Etiology

The most important cause of MR in the United States is myxomatous degenerative disease of the MV, which occurs in approximately 2.4% of the population.¹ Other important causes of MR include rheumatic heart disease, infective endocarditis, ischemic heart disease, and dilated cardiomyopathy. Less frequently, MR can be caused by collagen vascular diseases, trauma, previous chest radiation, the hypereosinophilic syndrome, carcinoid disease, and exposure to certain drugs.⁷⁰

Pathology

The MV apparatus consists of the mitral leaflets, chordae tendineae, papillary muscles, and mitral annulus, and abnormalities in any one of these components has the potential to cause MR.⁹² The system for classifying MR proposed by Carpentier focuses on the functional anatomic and physiologic characteristics of the MV pathology, and proposes three basic types of diseased valves based on the motion of the free edge of the leaflet relative to the plane of the mitral annulus.⁹³

In Type I MR, valvular insufficiency occurs secondary to annular dilatation or leaflet perforation, and normal leaflet motion is maintained. Type II MR is seen in patients with mitral valve prolapse, and is due to prolapse of often thickened excessive leaflet tissue that gives the valve a “billowing” appearance, frequently in addition to ruptured or elongated chordae tendineae causing increased leaflet motion. Type III insufficiency, as seen in patients with rheumatic and ischemic heart disease, occurs from restricted leaflet motion, either during systole and diastole (Type IIIA) or during systole alone (Type IIIB).

Pathophysiology

The basic pathophysiologic abnormality of MR is the retrograde flow of a portion of the LV stroke volume into the left atrium during systole due to an incompetent MV or dilated MV annulus.

Acute severe MR can result from ruptured chordae tendineae, a ruptured papillary muscle, or infective endocarditis, and causes a sudden volume overload on both the left atrium and ventricle.⁷⁰ Although an acute increase in preload provides a modest increase in overall stroke volume, the left atrium and ventricle are unable to fully accommodate the regurgitant volume or maintain forward stroke volume in the acute setting due to a lack of remodeling.

Chronic MR generally has a more indolent course, with increasing volume overload of the left atrium and ventricle as the effective valve orifice size becomes larger. The resulting increase in left atrial and ventricular volume initially allows for an increase in the total stroke volume by Starling’s law and accommodation of the regurgitant volume, thus maintaining forward cardiac output and alleviating pulmonary congestion during the compensatory phase of chronic MR.⁹⁴ However, as the left atrium becomes more dilated, the development of AF becomes more likely, disrupting atrioventricular synchrony and predisposing to thrombus formation. Additionally, chronic volume overload may lead to LV contractile dysfunction, resulting in impaired ejection and end-systolic volume increases. LV dilatation and filling pressure may also worsen throughout the progression of MR, reducing cardiac output and causing congestion of the pulmonary vasculature. These changes herald LV decompensation and heart failure, and often indicate significant irreversible injury to the ventricular myocardium.

Clinical Manifestations

In cases of acute severe MR, patients are often very symptomatic and present with pulmonary congestion and reduced forward stroke volume. In very severe cases, patients may present with cardiogenic shock.¹ Because the LV has not remodeled in the acute setting, a hyperdynamic apical impulse may not be present in the precordium. The typical systolic murmur of MR may be holosystolic or absent, with a third heart sound and/or diastolic flow murmur being the only auscultatory findings.

In cases of chronic MR, patients may remain asymptomatic for long periods of time due to the compensatory mechanisms of the remodeled LV. However, once the LV begins to fail, patients become increasingly symptomatic from exertional dyspnea, decreased exercise capacity, orthopnea, and eventually pulmonary hypertension and right heart failure.¹ Physical examination may demonstrate displacement of the LV apical impulse due to cardiac enlargement from chronic volume overload, and a third heart sound or early diastolic flow rumble. The characteristic auscultatory findings also include an apical systolic murmur which is variably transmitted to the axilla or the left sternal border, depending on the location of the pathology. As mentioned previously, patients may present with AF due to dilatation of the left atrium. Findings consistent with pulmonary hypertension frequently indicate late-stage disease.

Diagnostic Studies

In the setting of acute heart failure, TTE should be performed and may demonstrate the anatomical location and severity of the MV pathology. However, TTE may underestimate lesion severity due to inadequate views of the color flow jet. In this case, severe MR should be suspected if hyperdynamic systolic function of the LV is visualized, and TEE may be used to confirm the diagnosis and direct repair strategies. ⁹⁵ In the hemodynamically stable patient, coronary angiography should be performed preoperatively in the majority of patients so that myocardial revascularization may be performed in combination with MV surgery if necessary.⁷⁰

In cases of chronic MR, EKG and chest X-ray are performed to assess rhythm status and the degree of pulmonary vascular congestion.⁷⁰ An initial two-dimensional and Doppler TTE should be performed for a baseline estimation of LV and left atrial size, LV systolic function, pulmonary artery pressure, MV morphology, and MR severity.⁹⁶ A central color flow jet in the setting of a structurally normal MV on TTE suggests functional MR, which may be due to LV dilatation or tethering of the posterior leaflet in patients with coronary artery disease. In the setting of organic MR, which is suggested by the presence of an eccentric color flow jet and morphological abnormalities in the MV apparatus on TTE, the presence of calcium in the annulus or leaflets, the redundancy of the leaflets, and the anatomy of the MV pathology should be assessed. Follow-up TTE is indicated on an annual or semiannual basis in patients with asymptomatic moderate to severe MR in order to assess changes from baseline parameters and direct the timing of surgery. Any abrupt change in signs or symptoms in a patient with chronic MR is also an indication for TTE examination.⁷⁰

Additional preoperative studies are variably indicated in certain patient populations. Preoperative TEE is indicated in patients with poor diagnostic windows on TTE in order to determine the severity and anatomic basis of MR, and to evaluate LV systolic function.⁷⁰ Preoperative TEE is also indicated in cases when discrepancy exists between a patient’s functional status and the severity of MR on TTE, and is helpful for preoperative planning when assessing the feasibility of repair in the individual patient. Exercise stress-echocardiography may also be useful to detect LV systolic dysfunction in well-compensated patients, who may not demonstrate a rise in the end-systolic dimension of the heart or a drop in ejection fraction on routine TTE.⁹⁷ Coronary angiography should be performed prior to valve surgery in patients with evidence of ischemia, decreased LV systolic function, a history of coronary artery disease or coronary risk factors, including postmenopausal status and age ≥35 in men and premenopausal women.⁷⁰

Indications for Operation

Based on the morphology and severity of MR (Table 21-10), MV repair, MV replacement with preservation of part or all of the mitral apparatus, or MV replacement with removal of the mitral apparatus may be variably performed for the treatment of MR. As the intraoperative findings may dictate MV replacement whenever a MV repair is planned, current recommendations are for MV surgery in general (Table 21-11).⁷⁰

Mitral Valve Operative Techniques and Results

Mitral valve surgery is performed on the arrested heart with the assistance of cardiopulmonary bypass. Traditionally, a median sternotomy incision is used; however, the left atrium can also be approached via minimally-invasive incisions, such as a minithoracotomy or a partial sternotomy. The MV is commonly exposed through a left atrial incision placed posterior and parallel to the intra-atrial groove, or though a right atriotomy with transseptal incision.

Commissurotomy

Upon opening the left atrium, the MV is visualized and the left atrium is examined for thrombus. A nerve hook or right-angle clamp is subsequently introduced beneath the commissures and used to evaluate the MV apparatus for leaflet mobility, commissural fusion, and subvalvular chordal abnormalities. The commissure is then carefully incised in a slightly anterior direction 2 to 3mm at a time, making sure with each extension of the incision that the chordae tendineae remain attached to the commissural leaflets. The commissurotomy is generally stopped 1 to 2mm from the annulus where the leaflet tissue thins, indicating the transition to normal commissural tissue. The papillary muscles are subsequently examined and incised as necessary in order to maximize the mobility of the leaflets.

After the commissurotomy is complete, and the associated chordae tendineae and papillary muscles are mobilized, leaflet mobility is assessed. The anterior leaflet is grasped with forceps and brought through its complete range of motion. If subvalvular restriction or leaflet rigidity is identified, further division or excision of fused chordae and debridement of calcium may be necessary. Occasionally, the leaflets can be debrided carefully to increase mobility. Valve replacement may be more appropriate if extensive secondary mobilization is required. At the end of the procedure, competence of the valve is assessed with injection of cold saline into the ventricle.

Open surgical commissurotomy has an operative risk of <1%, and has been shown to have good long term results, with freedom from reoperation as high as 88.5%, 80.3%, and 78.7% at 10, 20, and 30 years, respectively.⁹⁸ The incidence of postoperative thromboembolic complications is generally <1% per patient-year, and the lack of required systemic anticoagulation precludes the development of hemorrhagic complications long-term.⁹⁹

Mitral Valve Replacement

After exposing the valve, an incision is made in the anterior mitral leaflet at approximately the 12 o’clock position, and leaflet tissue is excised as needed. The papillary muscles are reattached to the annulus and, if possible, the posterior leaflet along with its associated subvalvular structures are preserved. The annulus is subsequently sized, and an appropriate mitral prosthesis is implanted using pledgeted horizontal mattress sutures. The annular sutures may be placed from the atrial to the ventricular side, seating the valve intra-annularly, or from the ventricular to the atrial side, seating the valve in a supra-annular position. When placing the mattress sutures, care must be taken to stay within the annular tissue, as excessively deep bites may cause injury to critical structures such as the circumflex coronary artery posterolaterally, the atrioventricular node anteromedially, or the aortic valve anterolaterally. The sutures are subsequently placed through the sewing ring, and the valve prosthesis is lowered onto the annulus, where it is secured (Fig. 21-7).

The factors associated with increased operative risk for MV replacement include age, left ventricular function, emergent procedure status, NYHA functional status, previous cardiac surgery, associated coronary artery disease, and concomitant disease in another valve. However, for most patients, MV replacement is associated with an operative mortality between 2% to 6%, and 65% to 70% five-year survival.^100,101 Although preservation of the mitral apparatus during MV replacement is important for subsequent left ventricular function, there appears to be no difference between complete and partial preservation with respect to 30-day and 5-year mortality.¹⁰⁰ Mechanical valves are associated with increased durability compared to bioprosthetic valves, and have demonstrated a freedom from reoperation of 98% vs. 79% at 15 years, respectively.¹⁰² Despite these findings, the choice of prosthetic valve depends on many factors, and should be decided on a patient-by-patient basis.

Mitral Valve Repair

There are many techniques available for MV repair that are variably used depending on the intraoperative assessment of valvular pathology. On opening the atrium, the endocardium is examined for a jet lesion, a roughened area caused by a regurgitant jet striking the wall, in order to better localize the area of valvular insufficiency. The commissures are examined for evidence of prolapse, fusion, and malformation. The subvalvular apparatus and individual leaflets are subsequently examined, and areas of prolapse, restriction, fibrosis, and calcification are identified. Leaflet perforations are generally repaired primarily, or with a pericardial patch. The degree of annular dilation is also noted. The basic components of MV repair based on this assessment may include resection of the posterior leaflet, chordal shortening, chordal transposition, artificial chordal replacement, triangular resection of the anterior leaflet, and annuloplasty. Recent trends have been toward leaflet preservation.

One of the mainstays of MV repair is triangular resection of the posterior leaflet. Excision of the diseased leaflet tissue extends down towards but generally not to the mitral annulus. After repair has been completed, valvular competency is evaluated by injecting saline into the ventricle with a bulb syringe and assessing leaflet mobility and apposition. If focal insufficiency is identified in other areas, additional procedures are performed.

The anterior leaflet may be repaired via chordal shortening, chordal transposition, artificial chordal replacement, and triangular resection of the anterior leaflet. Chordal shortening has generally been abandoned in favor of chordal replacement. During chordal transposition, a resected portion of the posterior leaflet with attached chordae is transposed onto the prolapsed portion of the anterior leaflet to provide structural support, and followed with posterior leaflet repair as described above. The procedure of artificial chordal replacement uses polytetrafluoroethylene sutures to attach the papillary muscle to the free edge of the prolapsing anterior leaflet. Triangular resection with primary repair of the anterior leaflet removes the prolapsing segment of the anterior MV leaflet, while preserving adjacent chordal tissue, and may be especially helpful in patients with a ruptured chord or large amount of redundant anterior leaflet tissue.

Annular dilation is generally corrected using a MV annuloplasty device, such as a ring or partial band, and is known to improve the durability of MV repair (Fig. 21-8).¹⁰³ Several devices are available, and include rigid or semirigid rings that geometrically remodel the annulus, flexible rings or bands that restrict annular dilation while maintaining the physiologic sphincter motion of the annulus, and semirigid bands that provide a combination of annular remodeling and support of physiologic motion.

Another technique known as the “double-orifice” or “edge-to-edge” repair was introduced in 1995, and involves tacking the free edge of the anterior leaflet to the opposing free edge of the posterior leaflet.¹⁰⁴ This procedure effectively gives the valve a double-orifice “bow tie” configuration, and has been used as both a primary repair technique and an adjunct to other repair techniques, usually in cases of anterior leaflet pathology, or Barlow’s disease. While some groups report excellent late results, its use remains controversial.

Due to the variety in operations and etiologies of MV disease, there is heterogeneity in outcomes following MV repair. In general, the operative risk for patients undergoing MV repair is generally <1%, and late results across a broad range of patients have demonstrated benefits in survival and valve-related complications, such as thromboembolic events, infective endocarditis, and anticoagulation-related hemorrhage, compared to MV replacement.^69,84 Patients with MR due to degenerative disease have especially encouraging outcomes, demonstrating rates of survival and freedom from reoperation of >50% and >94% at 20 years, respectively.⁸⁴Historically, isolated anterior leaflet prolapse increased the risk of reoperation five-fold in this population. However, increasing experience and the expanded use of chordal replacement has greatly improved these results in recent series.¹⁰⁵ Independent predictors of mortality have included higher NYHA class, lower left ventricular ejection fraction, and age. Older patients have demonstrated slightly worse outcomes overall, with an operative mortality of approximately 4%, and a 10-year survival of 54% in patients ≥65 years of age. However, the superiority of repair over replacement persists even for patients >80 years of age.¹⁰¹

Patients with rheumatic disease have also demonstrated slightly worse outcomes, with one study showing significantly better freedom from operation at 10 years in patients with nonrheumatic MV disease (88% vs. 73%, p<.005).¹⁰⁶ Despite these differences in outcomes, MV repair remains the procedure of choice for the majority of patients with amenable MV disease.

Aortic Stenosis

Etiology

The most common cause of adult aortic stenosis (AS) is calcification of a normal trileaflet or congenital bicuspid aortic valve, particularly in patients >70 years of age. Another important cause of AS is rheumatic heart disease, which is particularly common in developing countries (Fig. 21-9).

Pathology

Calcific aortic valve disease, also known as senile or degenerative disease, is an age-related disorder characterized by lipid accumulation, proliferative and inflammatory changes, upregulation of angiotensin-converting enzyme activity, oxidative stress, and infiltration of macrophages and T lymphocytes.¹⁰⁷ This process, which closely resembles atherosclerotic vascular calcification, initially results in bone formation within the base of the cusps, reducing leaflet motion. Calcification progresses to involve the leaflets, and eventually results in obstructive disease, with a reduced effective valve area without signs of leaflet fusion.

Pathophysiology

In general, once moderate AS is present, the average rate of progression includes an increase in jet velocity of 0.3 m/s/year, an increase in mean pressure gradient of 7 mm Hg/year, and a decrease in valve area of 0.1 cm²/year (Table 21-12).⁷⁰ In most adult patients with AS, obstruction develops gradually and includes a long latent period free from symptoms. During this time, the left ventricle typically hypertrophies in response to systolic pressure overload, and normal intracavitary volume is maintained.¹⁰⁸ Afterload, which is defined as left ventricular systolic wall stress, and thus ejection fraction remain normal early in this process, as the increase in myocardial thickness is usually enough to counter increased intracavitary systolic pressures. Patients without a typical hypertrophic response to systolic pressure overload, or with a depressed contractile state of the myocardium, do not follow the common clinical course, but experience an early decrease in ejection fraction due to excessively increased afterload, without a compensatory response.¹⁰⁹

Concentric left ventricular hypertrophy without chamber dilatation eventually leads to increased end-diastolic pressures and early diastolic dysfunction. Forceful atrial contraction in the face of elevated end-diastolic pressures becomes an important component of ventricular filling, even as mean left atrial and pulmonary venous pressures remain in the normal range. Disorders such as atrial fibrillation that disrupt atrial contraction typically lead to clinical deterioration. Although systolic function is generally preserved long into the natural history of the disease, left ventricular decompensation eventually occurs in the setting of longstanding increased afterload and is an indication for surgery even in the absence of other symptoms.

Although concentric hypertrophy is a compensatory mechanism to maintain ejection fraction in the face of high intracavitary pressures, the hypertrophied heart becomes increasingly vulnerable to ischemic injury. Coronary blood flow may become inadequate, despite the absence of epicardial coronary artery disease.¹¹⁰ Coronary vasodilation is mitigated by the hypertrophied myocardium, and the hemodynamic stress of exercise or tachyarrhythmias can lead to subendocardial ischemia and further systolic or diastolic dysfunction. When ischemic injuries occur, patients with ventricular hypertrophy experience larger infarcts and higher mortality rates than those without hypertrophy.¹¹¹ In some patients, ventricular hypertrophy occurs in excess of what is needed to compensate for increased intracavitary pressures, creating a high-output state that is also associated with increased perioperative morbidity and mortality.¹¹²

Clinical Manifestations

The characteristic auscultatory findings of AS include a harsh, crescendo-decrescendo systolic murmur at the right second intercostal space, often with radiation to the carotid arteries.¹ As the disease progresses, aortic valve closure may follow pulmonic valve closure, causing paradoxical splitting of the second heart sound. Other physical findings associated with AS include an apical impulse commonly described as a “prolonged heave,” and the presence of a narrow and sustained peripheral pulse, known as pulsus parvus et tardus.

The classic symptoms of AS are exertional dyspnea, angina, and syncope.¹ Although many patients are diagnosed prior to the onset of symptoms, the most common clinical presentation in patients with a known diagnosis of AS followed prospectively is worsening exertional dyspnea due to a limited capacity to increase cardiac output with exercise, and a progressive rise in end-diastolic pressures leading to pulmonary congestion. Angina occurs in over half of patients with AS, and is due to the increased oxygen demand of the hypertrophied myocardium in the setting of reduced oxygen supply secondary to coronary compression. Although some patients may have concomitant ischemic disease, angina occurs without significant epicardial coronary artery disease in half of all patients with AS. Syncope is most common during exertion, as systemic vasodilation in the setting of a fixed cardiac output causes decreased cerebral perfusion. However, at times, it may occur at rest secondary to paroxysmal atrial fibrillation and subsequent loss of atrial booster pump function. Late findings of AS include atrial fibrillation, pulmonary hypertension, systemic venous hypertension, and rarely sudden death.

Diagnostic Studies

Evidence of left ventricular hypertrophy is found in approximately 85% of patients with AS on routine EKG, though the correlation between the absolute electrocardiographic voltages in precordial leads and the severity of AS is poor.¹ EKG also may demonstrate signs of left atrial enlargement, and various forms and degrees of atrioventricular or intraventricular block due to calcific infiltration of the conduction system. Routine chest X-ray usually demonstrates a normal heart size, with rounding of the left ventricular border and apex. Cardiac enlargement on chest X-ray is a sign of left ventricular failure and cardiomegaly, and is a late finding.

Transthoracic echocardiography is indicated in all patients with a systolic murmur graded ≥2/6, a single second heart sound, or symptoms characteristic of AS.⁷⁰ Initial TTE examinations are often diagnostic, and provide an assessment of left ventricular size and function, the degree of left ventricular hypertrophy, the degree of valvular calcification, and the presence of other associated valvular disease. Doppler evaluation should be performed to define the maximum jet velocity, which is the most useful measure for following disease severity and predicting clinical outcome.¹Additionally, color flow Doppler assesses the severity of the stenotic lesion by allowing calculations of the mean transvalvular pressure gradient, and effective valve orifice area (Table 21-12).⁷⁰ Follow-up TTE is variably indicated depending on the severity of AS in order to assess changes from baseline parameters and direct the timing of surgery: yearly for severe AS; every 1 to 2 years for moderate AS; and every 3 to 5 years for mild AS. Any abrupt change in signs or symptoms in a patient with AS is an indication for TTE examination.

Additional preoperative studies may be necessary in some patients. Rarely, when TTE images are suboptimal, TEE or fluoroscopy may be indicated to assess the degree of valve calcification and effective valve orifice area. As in other patients with valvular heart disease, coronary angiography should be performed prior to aortic valve surgery in most patients.⁷⁰ Since the symptoms of AS oftentimes mimic those of ischemic disease, cardiac catheterization and coronary angiography may be necessary at the initial evaluation in patients with AS. Stress-echocardiography may also be useful in the asymptomatic patient with AS in order to elicit exercise-induced symptoms, or abnormal blood pressure responses during exertion. It is also useful in the evaluation of low-gradient AS in patients with depressed LV function.⁷⁰ However, exercise stress-echocardiography is contraindicated in patients with ischemic heart disease.⁷⁰ In patients with evidence of aortic root disease by TTE, chest computed tomography is useful in evaluating aortic dilatation at several anatomic levels, and is necessary for clinical decision making and surgical planning.¹

Indications for Operation

Based on the severity of AS and the overall physical condition of the patient (Table 21-12), AVR may be recommended for the treatment of AS (Table 21-13).⁷⁰ In patients with severe calcific AS, AVR is the only effective treatment, though controversy exists as to the timing of intervention in asymptomatic patients. Balloon valvotomy creates a modest hemodynamic effect and temporary symptom improvement in patients with calcific AS. However, the procedure has not been shown to affect long-term outcomes, and is often used in high-risk patients in which the contribution of the AS to the patients’ symptoms is a matter of debate.¹¹³

Aortic Insufficiency

Etiology

The most common cause of isolated aortic insufficiency (AI) in patients undergoing AVR is aortic root disease, and represents over 50% of such patients in some studies.¹ Other common causes of AI include congenital abnormalities of the aortic valve such as bicuspid aortic valve, calcific degeneration, rheumatic disease, infective endocarditis, systemic hypertension, myxomatous degeneration, dissection of the ascending aorta, and Marfan syndrome. Less common causes of AI include traumatic injuries to the aortic valve, ankylosing spondylitis, syphilitic aortitis, rheumatoid arthritis, osteogenesis imperfecta, giant cell aortitis, Ehlers-Danlos syndrome, Reiter’s syndrome, discrete subaortic stenosis, and ventricular septal defects with prolapse of an aortic cusp.⁷⁰ Although most of these lesions produce chronic aortic insufficiency, rarely acute severe aortic regurgitation can result, often with devastating consequences.

Pathology

Regardless of its cause, AI produces volume overload with dilation and hypertrophy of the left ventricle, and subsequent dilation of the MV annulus. Depending on the severity of AI, the left atrium may undergo dilation and hypertrophy as well. Frequently, the regurgitant jet causes endocardial lesions at the site of impact on the left ventricular wall.

Diseases causing AI can be classified as primary disorders of the aortic valve leaflets, and/or disorders involving the wall of the aortic root. Diseases causing dilation of the ascending aorta are a more common indication for AVR due to isolated AI, and include disorders such as age-related (degenerative) aortic dilation, cystic medial necrosis of the aorta as is seen in Marfan syndrome, aortic dilation secondary to bicuspid valves, and aortic dissection, to name a few.¹¹⁴ In these disorders, the aortic annulus becomes dilated, causing separation of the valve leaflets and subsequent AI. The diseased aortic wall may dissect secondarily and further escalate regurgitation across the valve, and secondary thickening and shortening of the valve cusps may occur due to undue tension placed on the valvular apparatus by the dilated aortic root. As the disease progresses, the valves become too small to close the aortic orifice, causing further aortic insufficiency and exacerbating dilation of the ascending aorta.

There are also many primary valvular diseases that cause AI, generally in association with AS. One such disorder is age-related calcific AS, which causes some degree of AI in up to 75% of patients.¹ Infective endocarditis may involve the aortic valve apparatus and cause AI through direct destruction of the valve leaflets, perforation of a leaflet, or formation of vegetations that interfere with proper coaptation of the valve cusps. Rheumatic disease causes fibrous infiltration of the valve cusps and subsequent retraction of the valve leaflets, inhibiting apposition of the cusps during diastole and producing a central regurgitant jet. Patients with large ventricular septal defects or membranous subaortic stenosis may develop progressive AI, owing to a Venturi effect that results in prolapse of the aortic valve leaflets.

Pathophysiology

The basic pathophysiologic abnormality of AI is the retrograde flow of a portion of the LV stroke volume into the left ventricle during diastole, producing left ventricular volume overload.

Acute severe AI results most commonly from infective endocarditis, acute aortic dissection, or trauma, and causes a sudden volume overload on the left ventricle.³¹ Although an acute increase in preload provides a small increase in overall stroke volume due to the Starling mechanism, the left ventricle is unable to accommodate the large regurgitant volume and maintain forward stroke volume in the acute setting due to a lack of remodeling. Left ventricular end-diastolic and left atrial pressures increase dramatically, as the left ventricle is unable to develop compensatory chamber dilation. Although tachycardia develops as a compensatory mechanism to maintain forward flow, this attempt is often inadequate, and patients frequently present in heart failure and even cardiogenic shock. Moreover, subendocardial myocardial ischemia frequently develops as a result of decreased coronary diastolic perfusion pressures and increased left ventricular end-diastolic pressure, as well as increased myocardial oxygen demand due to acute dilation. In the setting of a chronic ventricular hypertrophy and preexisting diastolic dysfunction, the pressure-volume relationship is even more extreme, exacerbating the hemodynamic derangements seen in acute AI.

Chronic AI generally has a more indolent course, with volume overload of the left ventricle causing compensatory increases in left ventricular end-diastolic volume and chamber compliance, and a combination of eccentric and concentric hypertrophy.¹¹⁵ Compensatory remodeling of the left ventricle allows for accommodation of the regurgitant volume without a significant increase in filling pressures, and maintains the preload reserve of the chamber. Eccentric left ventricular hypertrophy develops, permitting normal contractile performance across the enlarged chamber circumference and subsequent ejection of a larger total stroke volume in order to maintain forward flow, despite the regurgitant fraction.^115,116 However, the enlarged chamber size results in an increase in systolic myocardial wall stress, and causes further ventricular hypertrophy. As the disease progresses, recruitment of preload reserve and compensatory hypertrophy maintains ejection fraction within the normal range despite elevated afterload, causing many patients to remain asymptomatic throughout the compensatory phase. ^115,117

Eventually, left ventricular compensatory mechanisms fail and systolic dysfunction ensues. As the disease progresses, preload reserve may become exhausted, the hypertrophic response may become inadequate, and/or impaired myocardial contractility may develop so that ejection fraction begins to decline. ¹¹⁸Although left ventricular systolic dysfunction related to excessive afterload is reversible early in the course, irreversible damage occurs once chamber enlargement predominates as the primary cause of diminished myocardial contractility.

Clinical Manifestations

In cases of acute severe AI, patients are symptomatic and invariably present with compensatory tachycardia, often associated with acute pulmonary congestion and cardiogenic shock.¹ Because the left ventricular and aortic pressures often equalize before the end of diastole, the diastolic murmur of AI may be short and/or soft. The reduced systolic pressure may attenuate the increase in peripheral pulse pressure seen in chronic AI, and early closing of the mitral valve due to elevated left ventricular end-diastolic pressures may diminish the intensity of the first heart sound in the acute setting.

In patients with chronic AI, symptoms of heart failure and myocardial ischemia develop after the compensatory phase.¹ Patients gradually begin to complain of exertional dyspnea, fatigue, orthopnea, and paroxysmal nocturnal dyspnea, often after significant myocardial dysfunction has developed. Angina is a common complaint late in the course, especially during sleep when heart rate slows and arterial diastolic pressure falls. Patients may also experience exertional angina secondary to diminished coronary perfusion in the setting of myocardial hypertrophy. Occasionally, the compensatory tachycardia that develops with chronic AI will cause palpitations, and the increased pulse pressure will cause a sensation of pounding in the patient’s head. Peripherally, the widened pulse pressure causes a forceful, bounding, and quickly collapsing pulse known as Corrigan’s or water-hammer pulses. Premature ventricular contractions have been reported to cause particularly troubling symptoms, owing to the heave of the volume-loaded left ventricle during the postextrasystolic beat. The classic auscultatory finding associated with AI is a high-pitched decrescendo diastolic murmur heard best in the left third intercostal space; an associated S₃ gallop is often indicative of late disease. The Austin Flint murmur has also been described, and is heard as a middiastolic rumble at the apex that simulates mitral stenosis, and occurs in severe AI when the regurgitant jet impedes mitral opening.

Diagnostic Studies

In the acute setting, TTE should be performed to confirm the presence and severity of aortic regurgitation, the degree of pulmonary hypertension, and the cause of valvular dysfunction.⁷⁰ When aortic dissection is suspected as the cause of acute AI, TEE should be performed for diagnosis, though chest computed tomography may be substituted if more readily available.^119,120 Cardiac catheterization, aortography, and coronary angiography are rarely indicated, and often delay necessary urgent surgical intervention.

In cases of chronic AI, the EKG frequently demonstrates signs consistent with left axis deviation and, late in the course, intraventricular conduction defects associated with left ventricular dysfunction. On chest X-ray, the left ventricle enlarges predominantly in an inferior and leftward direction, causing marked increase in the long axis diameter of the heart, frequently with little or no change in the transverse diameter. The chest X-ray should be examined for aneurysmal dilation of the aorta.¹ An initial TTE should be performed to confirm the diagnosis and severity of AI, assess the cause of AI (including valve morphology, and aortic root size and morphology), and assess the degree of left ventricular hypertrophy, volume, and systolic function.⁷⁰ Follow-up TTE is indicated on an annual or semiannual basis in patients with asymptomatic moderate to severe AI in order to assess changes from baseline parameters and direct the timing of surgery. Any abrupt change in signs or symptoms in a patient with chronic AI is also an indication for TTE examination.

Additional preoperative studies are variably indicated in certain patient populations.⁷⁰ In patients with poor windows on TTE, TEE, or magnetic resonance imaging is indicated for initial and serial assessment of AI severity, and left ventricular volume and function at rest. In symptomatic patients with chronic AI, it is reasonable to proceed directly to TEE or cardiac catheterization if TTE examinations are inadequate. Exercise stress testing may be helpful for an assessment of functional capacity and symptomatic responses in patients with a history of equivocal symptoms. Coronary angiography should be performed prior to valve surgery in most patients.⁷⁰

Indications for Operation

Based on the morphology and severity of valve dysfunction (Table 21-12), AV repair or replacement may be performed for the treatment of AI (Table 21-13).⁷⁰ Although the indications for AV repair and AV replacement do not differ, it is recommended that AV repair be performed only in those surgical centers that have developed the appropriate technical expertise, gained experience in patient selection, and demonstrated outcomes equivalent to those of valve replacement.

Aortic Valve Operative Techniques and Results

Aortic valve surgery has traditionally been performed through a median sternotomy incision with the assistance of cardiopulmonary bypass and moderate systemic hypothermia. However, minimally invasive incisions for aortic valve surgery have been introduced, including mini-sternotomy and mini-thoracotomy approaches. After the aorta is cross-clamped, cold blood cardioplegia is delivered antegrade through the aortic root, and/or retrograde through the coronary sinus. A left ventricular vent may be inserted through the right superior pulmonary vein to help maintain a bloodless field during the procedure, and to aid in de-airing at the conclusion of the operation.

Aortic Valve Replacement

During aortic valve replacement, an aortotomy is performed, extending medially from approximately 1to 2cm above the right coronary artery and inferiorly into the noncoronary sinus, and the valve is completely excised. The annulus is thoroughly debrided of calcium deposits. After the calcium has been removed, the ventricle is copiously irrigated with saline. At this point, the annulus is sized and an appropriate prosthesis is selected. Pledgeted horizontal mattress sutures are then placed into the aortic valve annulus and subsequently through the sewing ring of the prosthetic valve, taking care to avoid damage to the coronary ostia, the conduction system, and the MV apparatus. The annular sutures may be placed from below the annulus, seating the valve supra-annularly, or from above the annulus for intra-annular placement (Fig. 21-10).

The major components to increased operative risk associated with surgical AVR include age, body surface area, diabetes, renal failure, hypertension, chronic lung disease, peripheral vascular disease, neurologic events, infectious endocarditis, previous cardiac surgery, myocardial infarction, cardiogenic shock, NYHA functional status, and pulmonary hypertension. For most patients, the risk associated with AVR is 1% to 5%, and 5-year survival has been reported to be >80%, even in patients >70 years of age.^69,121 The choice of valve is dependent on many patient-related factors, and is accompanied by the attendant postoperative risks of decreased durability, and thromboembolic vs. hemorrhagic complications for biological and mechanical valves, respectively.

Aortic Valve Repair

Although aortic valve replacement is performed more commonly, AV repair may be recommended at surgical centers with extensive experience, technical expertise, and outcomes equivalent to valve replacement. ⁷⁰

For patients with aortoannular ectasia, AI is due to annular dilatation and distortion of the sinotubular junction. For these patients, competence of the aortic valve can be achieved by functionally repairing the annulus in a method analogous to homograft implantation. The aneurysmal portion of the aortic root is excised, and the aortic valve is reimplanted inside a tubular Dacron graft, with concomitant reimplantation of the coronary arteries. Alternatively, the aneurysmal tissue and supravalvular tissue can be excised in their entirety, with subsequent implantation of the Dacron graft onto the superior aspect of the annulus and reimplantation of the coronary arteries.

Valve-sparing root replacement for root and annular stabilization in patients with AI due to aortoannular ectasia has led to a more durable outcome than is seen with subcommissural annuloplasty or leaflet-related procedures alone. One study demonstrated equivalent overall survival between patients undergoing subcommissural annuloplasty or aortic valve repair without annuloplasty, and patients undergoing valve-sparing root replacement at 6 years. ¹²² However, patients that underwent valve-sparing root replacement had higher freedoms from reoperation and aortic insufficiency >2+ (100% vs. 90%, P=0.03; and 100% vs. 77%, P=0.002, respectively) at midterm follow-up.

For patients with AI associated with redundant leaflet tissue, aortic valve repair may be accomplished with free margin plication or resuspension of the valve cusps, with or without triangular resection of the redundant segment. Excision of the diseased portion of the involved valve cusp improves symmetry of the valve leaflets, and annular plication of one or both commissures helps to ensure adequate coaptation. Generally, the free margins of the excised leaflets are reapproximated primarily, but in the absence of adequate cusp tissue, a triangular autologous or bovine pericardial patch may be used for cusp restoration.

AV cusp repair with a free margin plication or resuspension technique has demonstrated encouraging results, both in patients with tricuspid and bicuspid aortic valves. Freedom from AV reoperation in patients with a tricuspid AV has been reported to be 89% to 92% at 10 years, with a freedom from recurrent AI >2+ of 80% to 86% at the same time point. In patients with bicuspid aortic valves, who generally represent a younger cohort of patients, 10-year survival has been reported at 94% following AV repair, with a freedom from AV reoperation of 81% at the same time point. ¹²³

Ross Procedure

As mentioned previously, the Ross procedure involves replacing the diseased AV with the patient’s native pulmonary valve as an autograft, which is in turn replaced with a homograft in the pulmonic position.⁸⁰ The autograft may be implanted in the aortic position directly with resuspension of the valve commissures, or in association with a root replacement, which requires reimplantation of the coronary ostia.

The cylinder root replacement technique is most reproducible, and involves transecting the native aorta approximately 5mm above the sinotubular ridge, with subsequent excision of the aortic valve leaflets and supra-annular tissue. The main pulmonary artery is transected at the bifurcation and the right ventricular outflow tract is incised, allowing the pulmonary valve and artery to be removed en bloc from the outflow tract. The annulus of the pulmonary autograft is sewn to the native aortic annulus with continuous or interrupted sutures, and the coronary ostia are reimplanted into the pulmonary artery graft. The pulmonary valve and right ventricular outflow tract are subsequently reconstructed using homograft tissue.

The primary benefit of the Ross procedure compared to traditional AV surgery is a low risk of thromboembolism without the need for systemic anticoagulation. Although patients undergoing the Ross procedure are generally younger, perioperative mortality has been reported to be as low as 2.5% in this group, with an overall survival of 90% at 18-year follow-up.¹²⁴ However, the long-term durability of the procedure is somewhat questionable. Although Ross reported a freedom from autograft replacement of 75% at 20 years, other groups have reported freedom from autograft reoperation and allograft reintervention of 51% and 82%, respectively, at 18-year follow-up.^124,125 Progressive aortic insufficiency has been described as a cause of late failure in these patients, as well as calcification of the pulmonary homograft and pulmonary stenosis.

Transcatheter Aortic Valve Replacement

Transcatheter aortic valve replacement (TAVR) is relatively new technology that has proven beneficial for the treatment of AS in seriously ill patients who are not candidates for conventional surgery. The procedure remains the focus of ongoing clinical trials, and thus there are no published indications for operation endorsed by the American College of Cardiology or the American Heart Association. However, the Edwards SAPIEN heart-valve system that has been used thus far in the TAVR experience has been recently approved by the Food and Drug Administration for labeled-indications associated with published early results.

The Edwards SAPIEN heart-valve system consists of a trileaflet bovine pericardial valve with a balloon-expandable stainless steel support frame, and can be inserted by either the transfemoral, transaortic, or transapical route. The transfemoral route involves performing a standard balloon aortic valvuloplasty, followed by transfemoral insertion of either a 22- or 24-French sheath, depending on the size of the valve selected for implantation. The balloon catheter and overlying collapsed bioprosthetic heart valve is then advanced across the native aortic valve under fluoroscopy, and deployed during rapid right ventricular pacing. If the patient’s peripheral vascular system is not amenable to femoral arterial cannulation, the transapical or transaortic route is chosen. In the transapical approach, a small intercostal incision is performed over the left ventricular apex, and a dedicated delivery catheter is inserted through the left ventricular apex and across the native aortic valve as described above. The transaortic approach is usually done through a ministernotomy. Other approaches that have been described include transaxillary, transsubclavian, and transcarotid. The particular role of each approach in a specific patient still remains to be defined, and continues to change as the technology improves.

A large multicenter clinical trial has been performed on patients that were judged to be too high risk or inoperable for traditional AVR, based on assumed risks of ≥10% to 15% and ≥50% 30-day mortality, respectively. In patients that had previously been deemed inoperable, TAVR markedly reduced the rate of death from any cause (49.7% vs. 30.7%, P = <0.001), the rate of death from cardiovascular causes (41.9% vs. 19.6%, p = <.001), and the rate of repeat hospitalization (44.1% vs. 22.3%, p = <.001) at one year compared with standard medical therapy.¹²⁶ Although the rates of neurological events (10.6% vs. 4.5%, P = 0.04), major vascular complications (16.8% vs. 2.2%, P = <.001), and major bleeding events (22.3% vs. 11.2%, P = 0.007) were higher in the TAVR group, these patients also experienced a significant reduction in symptoms and increased functional capacity compared with patients receiving standard medical therapy. In patients at high risk for traditional AVR, the rate of death from any cause, and from cardiovascular causes, was found to be noninferior in the TAVR group, compared with the surgical group.¹²⁷ The rate of major bleeding events was higher in the surgical group (19.5% vs. 9.3%, P= <0.001) at 30 days, and patients in the TAVR group had a significantly shorter length of stay in the intensive care unit (3 vs. 5 days, P = <0.001), and a shorter index hospitalization (8 vs. 12 days, P = <.001). Although more patients in the TAVR group experienced a reduction in symptoms to NYHA class II or lower (P = <0.001), they also experienced more neurological events (8.3% vs. 4.3%, P = 0.04), and major vascular complications (11.3% vs. 3.5%, P = <.001) at one year.

Although it is clear that TAVR represents a distinct set of periprocedural risks, it has demonstrated benefits in morbidity and mortality, especially in patients deemed inoperable for surgical AVR. Ongoing trials are examining the potential role of TAVR in patients with AS at moderate risk for traditional AVR.

Tricuspid Stenosis and Insufficiency

Etiology

Acquired tricuspid valve (TV) disease can be classified as either organic or functional, and affects approximately 0.8% of the general population.¹²⁸ Tricuspid stenosis is almost always a result of organic disease, namely rheumatic heart disease and endocarditis. In the case of rheumatic disease, tricuspid stenosis with or without associated insufficiency is invariably associated with mitral valve disease. Other less common causes of obstruction to right atrial emptying include congenital tricuspid atresia, right atrial tumors, and endomyocardial fibrosis.

Tricuspid insufficiency, on the other hand, is most often a functional disease caused by secondary dilation of the tricuspid annulus due to pulmonary hypertension and/or right heart failure. This is most commonly caused by MV disease. Conditions such as right ventricular infarction and pulmonic stenosis can also lead to increased right ventricular pressures and functional tricuspid insufficiency (TI). The less common causes of organic TI, with or without associated stenosis, include carcinoid syndrome, radiation therapy, trauma such as repeated endomyocardial biopsy specimens, and Marfan syndrome.

Pathology

The changes associated with tricuspid stenosis (TS) closely resemble those associated with MS, including fusion of the commissures.¹²⁸ In the case of rheumatic disease, mixed TS and TI may result from fusion and shortening of the chordae tendineae, and fusion of the commissures, causing retraction of the valve leaflets. The right atrium is frequently dilated and thickened in chronic TS, and chronic obstruction to right ventricular filling often produces signs of systemic venous congestion such as hepatomegaly and splenomegaly.¹

In most cases of TI, dilation and deformation of the tricuspid annulus is the most prominent feature; the valve leaflets oftentimes appear stretched, but are otherwise pliable and normal in appearance.¹ When TI is caused by carcinoid syndrome, white fibrous carcinoid plaques are found on the ventricular surfaces of the TV, causing the cusps to adhere to the underlying right ventricular wall and stenting the valve open.¹

Pathophysiology

The basic pathophysiologic abnormality of both TS and severe TI is elevated right atrial pressures, producing signs of systemic congestion and right heart failure. Severe TS is marked by a valve area <1.0 cm², and severe TI is defined as a vena contracta width of >0.7 cm in combination with systolic flow reversal in the hepatic veins.⁷⁰ However, in patients with TS, a diastolic pressure gradient of only 5 mm Hg, or a TV orifice <1.5 cm², is frequently enough to cause jugular venous distention, organomegaly, and peripheral edema. In severe cases, cardiac output is compromised, especially during exercise when the fixed obstruction prevents an increase in forward flow. Patients with severe insufficiency and pulmonary hypertension experience similar hemodynamic derangements.

Clinical Manifestations

Patients with TS and severe TI develop symptoms of right heart failure associated with chronically elevated right atrial pressures.¹ The classic clinical signs and symptoms of TS and severe TI are jugular venous distention, hepatomegaly, splenomegaly, ascites, and lower extremity edema. Uncomfortable fluttering in the neck has been reported in patients with TV disease, and sensations of throbbing in the eyeballs and pulsatile varicose veins have been reported to occur, especially in patients with severe TI.

The low cardiac output occasionally associated with TS and severe TI can cause fatigue, weakness, and exercise intolerance in these patients. In the absence of pulmonary hypertension, dyspnea is not a prominent feature of tricuspid disease. The auscultatory findings associated with TS include a presystolic and middiastolic murmur characterized by a tricuspid opening snap that increases on inspiration. The lower left parasternal murmur of TI may be holosystolic or less than holosystolic, depending on the degree of regurgitation, may be associated with a middiastolic murmur in severe cases, and may increase on inspiration.

Diagnostic Studies

In patients with TV disease, chest X-ray frequently demonstrates enlargement of the right atrium and ventricle. Patients with TS demonstrate an exaggerated a wave and a diminished rate of y descent in the jugular venous pulse, while patients with TR have abnormal systolic c and v waves.¹ TTE examination should be performed in patients with TV disease in order to characterize the structure and motion of the TV, the size of the tricuspid annulus, and other cardiac abnormalities that may affect TV function.⁷⁰ In patients with a pulmonary artery systolic pressure >55mm Hg, TI commonly occurs in the setting of structurally normal valves; however, structural derangement of the TV apparatus is frequently present if TI is documented with a pulmonary artery systolic pressure <40mm Hg. Doppler TTE allows estimations of the severity of TI, the right ventricular systolic pressure, and the TV diastolic gradient.

Indications for Operation

As an isolated lesion, mild or moderate TV disease does not require surgical correction. However, patients with severe TV disease should be considered for surgical intervention, especially in the setting of right ventricular enlargement and impaired systolic function, as this improves life expectancy and the development of sequelae such as heart failure and atrial fibrillation.¹²⁸ Depending on the patient’s clinical status and the cause of TV dysfunction, TV repair and TV replacement be variably recommended for the treatment of TV dysfunction (Table 21-14).⁷⁰ In patients with TI, the valve can usually be repaired with modern techniques.

Operative Techniques and Results

The TV can be approached through a median sternotomy, a right thoracotomy, or minimally invasive port-based techniques. Surgery is performed with the assistance of cardiopulmonary bypass and, though TV surgery is usually performed on the beating heart, a brief period of cardioplegic arrest is rarely needed to allow for complete inspection of the interatrial septum, and close any defects that may be present.

TV repair may include a suture or ring annuloplasty as well as valvuloplasty, and multiple methods have been described.¹²⁸ Historically, bicuspidization of the TV was accomplished by a figure-of-eight suture plication of the annulus of the posterior leaflet; however, this technique has been essentially replaced by suture or ring annuloplasty. Suture annuloplasty is generally performed by placing 0 polypropylene pledgeted sutures along the base of the anterior and posterior leaflets, partially encircling the annulus. Ring annuloplasty can be accomplished by suturing the TV annulus to a variety of rigid or semirigid annuloplasty rings, which generally have an opening at the level of the anteroseptal commissure to avoid passing the anchoring sutures too close to the conduction system. Most surgeons favor ring over suture annuloplasty. In severe annular dilatation, augmentation of the anterior leaflet with autologous pericardium has been used with some success. Tricuspid valvuloplasty is infrequently performed and may include commissurotomy, triangular leaflet resection, primary perforation repair, and traditional leaflet repair techniques such as chordal transfer, shortening, and replacement, papillary muscle plication, tricuspid leaflet augmentation, and the edge-to-edge repair technique used in MV prolapse.

For patients with functional TV disease, TV repair is generally preferred to replacement due to favorable results without the associated risks of thrombosis and anticoagulation. In the setting of concomitant mitral valve surgery, TV repair has not been associated with additional perioperative complications, and 5-year freedom from reoperation has been impressive at 98%.⁸⁵ However, a subgroup of patients report late failure following TV repair, and this may be worse following suture annuloplasty compared with ring annuloplasty.

Prosthetic valve replacement may be necessary due to extensive leaflet destruction or marked annular dilatation not amenable to repair. In some cases, the valve prosthesis may be anchored directly to the leaflet tissue instead of the valve annulus, reducing the risk of injury to the conduction system.¹²⁸ If this technique is used, it should be confirmed that the residual tissue does not interfere with the movement of the prosthetic leaflets after implantation. Pledgeted sutures should be used, and may be placed on the ventricular or atrial side of the annulus.

Outcomes data following TV replacement are difficult to interpret, as most reports are in patients with previous TV surgery and/or signs of severe right heart failure. Operative mortality has been over 20% in some studies.¹²⁸ One study of 87 patients undergoing TV replacement between 1194 and 2007 showed an in-hospital mortality of only 1.4%. The choice of prosthetic valve is also somewhat controversial. Though bioprosthetic valves are more durable in the tricuspid than mitral or aortic positions, valve degeneration is an important cause of bioprosthetic valve dysfunction at reoperation. The increased risk of valve thrombosis seen with mechanical valves, however, underlines the need for rigorous systemic anticoagulation. Even with these precautions, mechanical tricuspid valves are associated with an increased risk of hemorrhagic and thrombotic complications. The choice of valve is usually decided on a case-by-case basis and late outcomes have been similar with biological and mechanical valves in this position. In general, TV replacement may be a reasonable choice in select patients, though more data are needed regarding long-term outcomes in the modern era.

Multivalve Disease

Pathology involving multiple valves is relatively common, and may result from diseases such as rheumatic fever, calcific disease, Marfan syndrome, and other connective tissue disorders.¹ However, multivalve disease may also be caused by secondary valvular dysfunction due to a distal valvular lesion, as in the case of myxomatous degeneration of the mitral valve, resulting in pulmonary hypertension, dilation of the tricuspid annulus, and functional TI. If the primary pathology is corrected early in the disease course, these secondary functional changes may resolve without further intervention.

In patients with multivalve disease, the clinical manifestations may be dependent on the severity of each individual valve lesion, but this is not always the case.¹ In patients with concomitant mitral and tricuspid dysfunction, the prominent symptoms of dyspnea, paroxysmal nocturnal dyspnea, and orthopnea commonly associated with MV dysfunction are frequently diminished by associated TV dysfunction. Symptoms of multivalve disease are most commonly masked when valvular abnormalities are of approximately equal severity, highlighting the importance of careful examination of each valve both preoperatively and in the operating room.

Surgery for multivalve disease is associated with a higher perioperative mortality than single-valve procedures, and this risk is exacerbated by factors such as pulmonary artery hypertension, age, triple-valve procedures, concomitant coronary artery bypass grafting, previous heart surgery, and diabetes.¹²⁹ Failing to recognize significant concomitant valvular dysfunction at the time of surgery is also associated with higher perioperative mortality. For this reason, patients suspected of having multivalve involvement should undergo full preoperative Doppler TTE or TEE evaluation, and heart catheterization.⁷⁰ In selected patients, procedures correcting multivalve disease demonstrate significant clinical improvement in symptoms and quality of life, as well as acceptable mortality and survival rates.¹²⁹

Epidemiology of Heart Failure

Heart failure affects approximately 5 million patients in the United States, with >550,000 new cases diagnosed annually.¹³⁰ The disorder is the primary reason for 12 to 15 million office visits and >1 million hospitalizations each year. Overall 1-year mortality is estimated to be around 25%, but this can increase to as high as 75% for patients with more advanced heart failure (NYHA class IV).¹³¹ While heart transplantation remains the gold standard for the treatment of end stage disease, an increasing number of patients deteriorate while on the waiting list and up to 30% die before transplantation.¹³² The total direct and indirect costs associated with the treatment of heart failure are estimated to be $32 billion, and this is projected to increase to $70 billion by 2030.¹³³ Advances in the surgical management of heart failure over the last decade have pushed surgery for CHF into the mainstream. As a result, there is an increasing number of patients with late- or end-stage disease who are being considered for surgical therapies.

Etiology and Pathophysiology

Heart failure can be classified as acute vs. chronic, genetic vs. acquired, left-sided vs. right-sided and systolic vs. diastolic dysfunction. The underlying causes and treatments for each of these vary considerably. In the Framingham Heart Study, coronary artery disease accounted for 67% of heart failure cases, valvular heart disease accounted for 10%, and 20% of cases were attributable to primary myocardial diseases, of which dilated cardiomyopathy predominated.¹³⁴ In all cases, heart failure is a progressive disorder that through complex mechanisms of ventricular remodeling, altered hemodynamics, neurohumoral activation, cytokine overexpression, and vascular and endothelial dysfunction either disrupts the ability of the myocardium to generate force or results in a loss of functioning cardiac myocytes, thereby preventing normal myocardial contraction.

CABG for Ischemic Cardiomyopathy

Surgical coronary revascularization is among the most commonly performed procedures for CHF. CABG is beneficial as it protects from further myocardial infarction and/or malignant ventricular arrhythmias. It is most successful when treating hibernating as opposed to infarcted myocardium.

While the majority of evidence supporting CABG for patients with ischemic cardiomyopathy comes from nonrandomized, retrospective studies, the prospective, randomized, multicenter international Surgical Treatment of Ischemic Heart Failure (STICH) trial compared CABG with medical therapy to medical therapy alone. Entry criteria included an EF ≤35% with CAD and anatomy suitable for CABG. No significant difference was seen in overall mortality by study completion, but patients who underwent CABG did have fewer deaths or hospitalizations from cardiovascular causes (58% vs. 68%, P<0.001).^135,136 This difference is despite the facts that only 50% of patients had myocardial viability testing, that 17% of patients in the medical therapy group underwent CABG and that 9% of patients randomized to CABG did not have surgery.

Myocardial viability testing has been shown by multiple studies to be pivotal in identifying patients that will have improved outcomes following CABG for ischemic cardiomyopathy.^137,138 A meta-analysis performed by Allman et al demonstrated an 80% reduction in mortality in patients who underwent revascularization with viable myocardium compared to patients who received medical therapy alone (3.2% vs. 16%, p<0.0001). Most important, in this analysis CABG had no benefit over medical therapy for patients without viable myocardium. A more recent study by Gerber et al prospectively compared CABG and medical therapy to medical therapy alone in 114 patients with CAD and low EF (24 ± 8) who underwent viability testing using delayed-enhancement cardiac MRI.¹³⁹ That study demonstrated worse 3-year survival in medically treated patients with dysfunctional but viable myocardium than in medically treated patients with nonviable myocardium (48% vs. 77%, P = 0.02). This corresponded with a 4.56 hazard of death of viable myocardium when medical treatment was selected over full revascularization. In contrast, survival after CABG was not significantly different whether myocardium was viable or not (88% vs. 71%, P = NS). These studies underscore both the importance of viable myocardium as well as the adverse consequences of not offering a patient with viability surgical intervention.

Patients with ischemic cardiomyopathy are a heterogeneous group, and, as with any surgery, appropriate patient selection is central to success. In one retrospective study of 96 patients with ischemic cardiomyopathy (EF ≤25%), age, and poor distal vessel quality were predictors of poor outcomes.¹⁴⁰ Mortality in patients with poor vessel quality was 100%, compared with 90% when vessel quality was fair and 10% when it was good. Therefore, poor vessel quality should be considered a contraindication to surgical revascularization even in the presence of angina.

LV size and LV dyssynchrony are also risk factors for adverse short and intermediate term outcomes. A LV end diastolic dimension of >100 mL/m2 is associated with a significantly reduced 5-year survival following CABG (85% vs. 53%, p<0.05), as well as worse 5-year freedom from recurrent CHF (85% vs. 31%).¹⁴¹ Moreover, LV dyssynchrony has been shown to have a significant impact on mortality in patients undergoing moderate to high risk revascularization and may compound risk in patients with nonviable myocardium.¹⁴² In patients with severe preoperative LV dyssynchrony the 30-day mortality was 27% vs. 3% in patients without significant dyssynchrony (p<0.001). Similar differences were seen with the presence of postoperative LV dyssynchrony, and outcomes were worse when patients also had fewer segments of viable myocardium.

Secondary Mitral Regurgitation

Secondary mitral regurgitation describes MR that results from damage to the left ventricle as a result of either ischemia or dilated cardiomyopathy rather than from a problem with the valve itself.¹⁴³ Ischemic MR (IMR) typically results from systolic restriction of the mitral leaflets due to tethering of the subvalvular apparatus. This occurs mainly from regional wall motion abnormalities in areas of the LV adjacent to papillary muscle attachments. Alterations in the size and shape of the mitral annulus and posterior displacement of the posteromedial papillary muscle, which occurs primarily after an inferoposterior MI, may also contribute. Additionally, functional MR (FMR) is caused by LV dilatation and increased sphericity, which displace the papillary muscles apically and radially, creating lateral forces on the valve that lead to increased retraction of the mitral leaflets by the chordae tendineae. LV dyssynchrony may also contribute to FMR through poor coordination of the contraction of the septum and lateral walls, producing MR that may vary in intensity during the cardiac cycle. Functional MR is usually referred to as a Carpentier class I/IIIb lesion due to the presence of both annular dilatation (Carpentier type I) and systolic restriction of the mitral leaflets due to LV dysfunction (Carpentier type IIIb). Ultimately, increased regurgitation leads to increased preload, LV wall tension, and LV work load, all of which contribute to progressive dysfunction of the LV and worsening heart failure.

Several observational and population based studies have demonstrated a significant impact of secondary MR on long-term survival. Following MI, the 5-year survival rate dropped significantly from 61% in patients who did not have MR to 47% and 29% in patients with mild and moderate to severe MR, respectively.¹⁴⁴ Similarly, in a series of 2,057 patients with symptomatic heart failure and a LVEF <40%, the 5-year survival rate for patients without MR was 54%, and it decreased to 40% in patients with moderate to severe secondary MR.¹⁴⁵ In a cox proportional hazards analysis, increasing severity of MR was an independent predictor of decreased survival (HR = 1.23, [1.13–1.34], p = 0.0001), and this observation held for patients with both ischemic and nonischemic disease etiologies. Moreover, medical therapy and PCI have not reduced the impact of IMR on late mortality.¹⁴⁶

Although specific recommendations to intervene for secondary MR are controversial and have not been rigorously defined, guidelines are available (Table 21-15).^70,147 Some surgeons initially advocated performing only revascularization in cases of moderate ischemic MR with the idea that revascularizing viable myocardium would lead to improvements in LV function and effect reverse remodeling, ultimately contributing to a decrease in MR. While several studies have shown that MR often persists following revascularization alone, the addition of a mitral valve annuloplasty in those studies did not improve long-term functional status or survival in patients with ischemic MR.^148,149,150 Nevertheless, other studies have shown that the persistence of MR after CABG is associated with a decreased survival rate and that CABG alone only has modest effects on reducing MR at 1 month follow-up.¹⁴³ As a result, a growing number of centers have elected to repair moderate MR in this patient population. Indications for surgery in ischemic MR patients in the absence of revascularization options are even less well-defined.

For patients with functional MR, the goal of mitral valve surgery is to avoid or postpone transplantation in eligible patients, but it should generally not be performed in patients with end-stage heart failure who present with low EF and limited myocardial viability. Those patients are often best suited by transplantation and/or ventricular assist device implantation.

Mitral valve repair is the procedure of choice when surgery is indicated for secondary MR. Currently, recommendations are to use a semirigid or rigid annuloplasty ring to downsize the mitral annulus.¹⁴³ There have also been various techniques proposed to correct the papillary muscle displacement, but most reports are single center, retrospective and small. Mitral valve replacement with preservation of the subvalvular apparatus is indicated when repair is not feasible due to severe tethering of the leaflets or massive LV dilation.

Outcomes from surgery vary between centers and amongst patients in this heterogeneous group. Operative mortality ranges between 0% to 9% in most modern series.¹⁴³ Generally speaking, mortality and recurrence rates are higher and long term prognosis is worse compared to outcomes for primary MR. Recurrent MR is as high as 15% to 30% in some series and 5-year mortality is between 44% to 48%.^143,151,152 Some reductions in left atrial dimension and LV reverse remodeling may be achieved.¹⁵³

Left Ventricular Aneurysmorrhaphy and Surgical Ventricular Restoration

Pathophysiology of Ventricular Aneurysms

A transmural infarction of approximately 5% to 10% of the myocardium may result in formation of an LV aneurysm as necrotic myocardium is replaced by fibrous tissue. This usually occurs 4 to 8 weeks following the infarct. In the last decade, prompt revascularization of the culprit artery by either surgical or interventional techniques generally results in sparing of the subepicardial muscle while the subendocardial muscle remains necrotic.¹⁵⁴ Therefore, it is not uncommon for the LV wall to show both living myocardium during thallium testing and an akinetic zone on echocardiogram or angiogram. It has been demonstrated that once more than 20% of the myocardium is necrosed there is irreversible progression to ventricular dilation and failure.¹⁵⁵ The classic aneurysm is a 4 to 6 mm thick scar, which bulges outward in paradoxical motion as the LV contracts during systole. More than 80% develop in the anteroseptal and apical portions of the left ventricle as a result of left anterior descending artery occlusion. The rest are inferior in location and the result of circumflex or right coronary occlusion.

This patient population typically suffers from associated ventricular arrhythmias for several reasons. First, electrical dyssynchrony results from postinfarction remodeling, and triggers for ventricular arrhythmias typically occur in the scar border zone in patients with ischemic cardiomyopathy.^156,157 Second, increased ventricular volume causes high wall stress and stretch, and stretch has been shown to be arrhythmogenic.¹⁵⁸ Third, LV aneurysms represent an independent risk factor for SCD after MI.¹⁵⁹ Surgical ventricular restoration (SVR) addresses each of these issues by removing the anatomic substrate during resection of the postinfarct scar and/or aneurysm, accomplishing volume reduction and mechanical resynchronization and relieving ischemia through complete revascularization and reduction in myocardial wall tension and oxygen demand.

Clinical Presentation and Diagnosis

Symptoms of LV aneurysms include angina, CHF, ventricular arrhythmias and rarely embolic phenomenon. Rupture is extremely uncommon. Patients generally present for coronary artery bypass or during evaluation of CHF or arrhythmias. While transthoracic echocardiography gives pertinent information regarding LV function, size, mitral valve function and the presence of thrombus, it is generally accepted that cardiac MRI is the best diagnostic modality to accurately identify areas of scar and viable tissue and to best define ventricular geometry.¹⁵⁵

Surgical Treatment and Results

In 1985, Vincent Dor described a surgical technique called the endoventricular circular patch plasty that was intended to improve geometric reconstruction compared with the standard linear repair in LV aneurysm surgery. SVR is a somewhat broader term that arose from surgical repair of ventricular aneurysms and has now come to be applied to a group of surgical procedures designed to correct the effects of postinfarction ventricular remodeling. It is also sometimes referred to as surgical ventricular remodeling or reconstruction, surgical anterior ventricular endocardial reconstruction (SAVER), or the Dor procedure. SVR is specifically intended to reduce the size and sphericity of the LV by excluding akinetic and dyskinetic areas, most often by using a circular patch inserted inside the ventricle on contractile myocardium (Fig. 21-11A & B).

Candidates for SVR are typically patients who have had a remote anterior or anteroseptal myocardial infarction, significant ventricular enlargement with a significant area of akinetic or dyskinetic myocardium, a discrete aneurysm, a clinical picture consistent with heart failure (LVEF <40%), retained function of the basilar and lateral portions of the heart and good right ventricular function. These patients should also be candidates for repair of any other concomitant cardiac disease. Dor currently emphasizes the importance of complete revascularization and repair of any mitral pathology at the time of operative SVR. In patients with spontaneous (13%) or inducible (25%) ventricular tachycardia (VT), it is additionally necessary to perform nonguided endocardial resection and cryoablation encircling the resected area.¹⁵⁵

Results with this approach have been good in treating both heart failure and its sequelae, such as VT. In Dor’s series of 1150 patients, the operative mortality was dependent on the EF and ranged from 1% for patients with EF >40% to 13% for patients with EF <30%, and the 5-year survival approached 85%.¹⁵⁵ Overall, more than 80% of survivors are either stabilized or improved, and quality of life has been shown to improve significantly by 6 months after the Dor procedure.¹⁶⁰ This is likely due in part to the fact that the Dor procedure restores LV geometry, resulting in a mean ejection fraction increase between 10% to 15%, with significant alleviation of symptoms.^{155,161,162,163} These data are reinforced by the international RESTORE group, which examined SVR in a registry of 1198 postinfarction patients between 1998 and 2003.¹⁶⁴ They found that 5-year overall freedom from hospital readmission for CHF was 78%. Moreover, 67% of patients had preoperative NYHA class III or IV symptoms, whereas 85% of patients were NYHA functional class I or II postoperatively.

With respect to VT, Dor et al. reported on 106 patients with ischemic ventricular arrhythmias that underwent reconstruction for postinfarction LV aneurysm and visually-directed endocardiectomy plus or minus cryoablation and coronary revascularization ¹⁶⁵. At a mean follow-up of 21.3 months, only 10.8% of patients had inducible VT and no spontaneous VT was documented. Results from similar series have also been excellent,^148,163,166 but the efficacy of left ventricular restoration alone has been controversial.^167,168 Inferior results seen in some series have been attributed to failure to perform endocardial resection and/or cryoablation at the border of the transitional zone, as well as differences in stimulation protocols and possible inadequate volume reduction of the ventricle.

Recently, a large, randomized, multicenter study, the STICH trial, has reported the conclusion that adding SVR to reduce ventricular volume to CABG does not improve symptoms or exercise tolerance and fails to lower death rate or cardiac rehospitalization compared to CABG alone¹³⁵. While this trial has some shortcomings, it has resulted in a marked decrease in referrals for this procedure The main problem is that the LV volume was reduced by only 19% in the STICH trial, reflecting an inadequate repair as determined by the Surgery Therapy Committee, whose “acceptable STICH procedure” guideline required a 30% reduction at the 4-month postoperative cardiac MRI.¹⁶⁹ Previous studies have reported an average reduction of end-systolic volume index (ESVI) of 40% with a range between 30% and 58%, suggesting that the STICH SVR procedure may have involved an inadequately small LV plication or limited intracavitary reconstruction.¹⁶⁹ Moreover, this trial enrolled 13% of patients who had never had an MI and changed criteria such that enrollment required documented LV anterior wall dysfunction rather than demonstration of scar. This could have captured patients with hibernating myocardium that would recover following CABG alone. Dor subsequently published the results of 117 patients who would have been eligible for the STICH trial and demonstrated durable improvement in left ventricular function.¹⁷⁰ However, this was a single-center, restrospective experience. Caution should be exercised so as not to broadly extrapolate the results of the STICH trial and inappropriately deny appropriate patients effective treatment.

Mechanical Circulatory Support

Intra-aortic Balloon Pump

The intra-aortic balloon pump (IABP) is the most commonly used device for mechanical circulatory support, and it may be easily deployed in the catheterization laboratory, in the operating room or at the bedside. The device is inserted percutaneously through the femoral artery into the thoracic aorta. It is synchronized so that the balloon is inflated during diastole and deflated during systole, resulting in augmentation of diastolic perfusion of the coronary arteries and decreased afterload. Typically, this improves cardiac index and decreases both preload and myocardial oxygen consumption.

The indication for use of an IABP is most often cardiogenic shock during or after cardiac catheterization or cardiac surgery. It also is indicated for preoperative stabilization of high-risk patients with either severe coronary artery disease, LV dysfunction, or refractory, unstable angina. Kang et al have reported that risk-adjusted mortality was significantly lower for selected high-risk patients undergoing open heart surgery when a preoperative IABP was used.¹⁷¹

Generally, an IABP is used for a few days and weaned as the patient’s condition improves. Morbidity associated with device use is typically minimal; however, in one series of 911 patients undergoing CABG who received an IABP, there was a 12% incidence of minor or major vascular complications, including an approximately 3% incidence of limb ischemia requiring thromboembolectomy. This is the most serious complication of IABP placement. To prevent this problem, frequent lower extremity neurovascular checks are necessary while an IABP is in place ¹⁷².

Ventricular Assist Device Indications and Cannulation

Patients in need of ventricular assist devices (VADs) may have preexisting chronic heart failure, refractory ventricular arrhythmias, or acute heart failure following an MI,cardiopulmonary arrest, viral illness, pregnancy, or cardiotomy. Device therapy is intended to preserve end-organ perfusion and function and may be categorized as short- or long-term support for the left heart, the right heart, or both. In general, VADs may be used for support while the heart recovers (bridge to recovery, BTR), while the patient waits for a heart transplant (bridge to transplant, BTT) or as a final option to treat a chronic heart failure patient who is not a transplant candidate (destination therapy, DT). The Interagency Registry for Mechanically Assisted Circulatory Support (INTERMACS) database, a joint effort by the NHLBI, FDA, CMS, academia, and industry to prospectively track patient outcomes, reported that between January 2009 and June 2010 indications for device implantation were BTR (1%), BTT (41%), bridge to decision (43%), DT (14%), and rescue therapy (0.5%).¹⁷³ However, the percentage of patients receiving a VAD as destination therapy is increasing as results and devices improve. In 2011, 38% of patients had a primary device strategy of DT, whereas only 23% were considered BTT.

Left ventricular assist devices (LVADs) provide support for the failing heart by unloading blood from the left ventricle and pumping it into the aorta. Cannulas may be inserted into the LV apex or the left atrium for inflow into the pump, and return is through an arterial cannula or graft sewn to either the ascending or descending aorta. For right sided devices, inflow drainage is most often from a cannula in the right atrium, and blood is returned through a graft sewn to the pulmonary artery or right ventricular outflow tract.

Left Ventricular Assist Devices

The first generation LVADs were pulsatile devices. They provided adequate support for the heart but were limited by their large size and durability.¹⁷⁴ More recently, continuous-flow LVADs based on rotary pump technology have been introduced. These devices are smaller, quieter, and durable enough for long term support. The two most commonly used devices today are the HeartMate II (Thoratec, Pleasanton, CA) and the HeartWare HVAD (HeartWare, Inc., Framingham, MA) (Fig. 21-12A & B, 21-13A & B). These devices differ in that the HeartMate II is implanted subdiaphragmatically, whereas the smaller HeartWare HVAD is implanted within the pericardium. Frequently used short-term support devices include the Abiomed BVS 5000 (Abiomed, Inc., Danvers, MA) and the CentriMag (Thoratec), which are both extracorporeal pumps, as well as the Impella (Abiomed), which may be inserted percutaneously. These devices are commonly used in either post-MI or postcardiotomy heart failure. They have the benefit of faster and easier insertion, making them ideal rescue devices and allowing time for patient transfer to a tertiary referral center, device weaning, transplantation, or transition to a permanent VAD as DT or BTT.

Bridge to Recovery

The ideal clinical situation would be for all LVADs to be temporary with the goal of myocardial recovery. However, as noted above, this is rare with only 1% of devices in the most recent INTERMACS data placed with intent for bridge to recovery.¹⁷⁵ The LVAD Working Group Recovery Study, a prospective multicenter trial investigating myocardial recovery in BTT patients, has shown significant improvements in left ventricular ejection fraction and significant reductions in left ventricular end-diastolic diameter following support with continuous flow pumps, but myocardial recovery resulting in device explantation was still only seen in six patients (9%).¹⁷⁶ Current data suggest that significant reverse remodeling is more likely to occur in the young and those with myocarditis.¹⁷⁷

Nevertheless, some encouraging results have been reported using a combination of treatment modalities. In a few small studies of patients with LVADs inserted for nonischemic cardiomyopathy, deliberate and aggressive medical therapy, including the β2-agonist clenbuterol resulted in successful LVAD explantation in 69% to 73% of patients,^178,179 but these results have been difficult to replicate. Moreover, early results from clinical trials using stem cell therapy to treat patients with ischemic cardiomyopathy suggest that stem cells may be another adjuvant treatment with potential to aid in myocardial recovery.^180,181

Bridge to Transplant

LVADs are used as a bridge to transplant in patients who are candidates for heart transplantation but are not predicted to survive the waiting list period due to sequelae of cardiac failure, including end-organ dysfunction, rising pulmonary artery pressures, escalating inotrope requirements, malignant ventricular arrhythmias, and risk for sudden death. Due to the scarcity of donor organs, the improved survival seen with LVAD usage has resulted in more patients remaining alive while on the transplantation waiting list. It is currently estimated that 35% of patients who go on to receive a heart transplant have had a previous LVAD implantation, although at more aggressive tertiary care facilities this number may be as high as 75% to 90%.¹³¹

The HeartMate II pump was evaluated as a BTT in an observational, prospective multicenter trial of 133 patients with persistent NYHA class IV heart failure despite optimal medical management who were status 1A or 1B on the transplant list.¹⁸² At 6 months, 100 patients (75%) had undergone transplantation, had cardiac recovery, or continued on mechanical support while remaining eligible for transplantation. There were significant improvements in both quality of life and functional status with device therapy. At 3 months, 81% of patients were in class I or II heart failure. Moreover, complications, including bleeding requiring reoperation, stroke, drive-line infection, and need for right ventricular assist device support, were significantly less frequent than with the previous generation HeartMate XVE.¹⁸³ These data led to FDA approval of the HeartMate II as a BTT LVAD in 2008, and clinical use of the device increased dramatically. More recently, a multicenter, prospective trial compared the HeartWare HVAD to contemporaneously inserted devices for use as a BTT.¹⁸⁴ This trial demonstrated noninferiority of the HeartWare HVAD, but in contrast to the 2007 trial, approximately 90% of patients in both groups were transplanted, explanted for recovery, or remained alive and eligible for transplant with LVAD support at 6 months. Most important, data suggest that patients bridged to transplant with an LVAD in the current era experience similar short- and long-term posttransplant survival and complications and do not have a higher incidence of allosensitization compared to standard cardiac transplant patients ^185,186.

Destination Therapy

The Randomized Evaluation of Mechanical Assistance for Treatment of Congestive Heart Failure (REMATCH) trial was conducted to compare the efficacy of LVAD insertion against optimal medical management in patients with NYHA class IV heart failure. While the pulsatile devices used in this trial had high failure rates, poor durability, and high associated mortality, there was still a clear survival benefit in patients treated with LVADs. This led to the FDA approval of the first LVADs for destination therapy in 2002.¹⁷⁴

Subsequent trials have proven the increased efficacy of second generation devices for DT. In one such landmark trial, patients with advanced heart failure who were ineligible for transplantation were randomized in a 2:1 ratio to either a HeartMate II or HeartMate XVE.¹⁸⁷ While both groups showed significant improvements in functional capacity and quality of life, actuarial survival at 2 years was superior for HeartMate II patients (58% vs. 24%, P=0.008) and adverse event rates were significantly lower. These data established the benefit of continuous flow LVADs over optimal medical management for end-stage heart failure, and led to FDA approval of the HeartMate II for DT in 2010. In certain populations, 2-year survival with the HeartMate II is now 80%.¹⁷⁵ Several smaller third generation devices are in various stages of development or clinical trials. Some of these devices eliminate the drive line by using alternative energy sources, thereby removing a significant nidus for device infections. Long-term outcomes with these devices are expected to continue to improve, approaching that of cardiac transplantation and providing a viable solution to organ shortage for many patients.¹⁷⁵

Current eligibility criteria for mechanical support as destination therapy include: (a) medically refractory NYHA class III or IV heart failure for at least 60 days, (b) peak oxygen consumption <12 ml/kg/min or failure to wean from continuous IV inotropes, (c) left ventricular ejection fraction <25%, and (d) presence of a contraindication for heart transplantation (i.e., age >65 years, irreversible pulmonary hypertension, chronic renal failure, insulin-dependent diabetes with end organ damage, or other clinically significant comorbidities).¹³¹ Once a patient has an LVAD inserted as DT, close and intensive follow-up by a multidisciplinary heart failure team is required in order to optimize medical therapy, reduce device-related morbidity and improve survival.

It is also important to keep in mind that while some contraindications to transplantation are irreversible, others can be modified. As such, approximately 10% of patients implanted with an initial strategy of destination therapy become BTT patients,¹³¹ and in some patients, the LVAD itself facilitates this transition. For example, an improvement in mean pulmonary vascular resistance was reported following implantation of the HeartMate II in patients with end-stage heart failure (2.1 vs. 3.6 Woods units, P<0.001).¹⁸⁸ These data are also relevant to the 43% of patients that receive LVADs as a bridge to decision.

Right Ventricular Assist Devices and Biventricular Assist Devices

Most patients who present with advanced heat failure and a failing left ventricle also have some degree of right-ventricular dysfunction, but the majority of these patients do well with only an LVAD. However, implantation of an LVAD may cause acute worsening of tricuspid regurgitation and exacerbations of right-heart failure through leftward deviation of the intraventricular septum and as a result of the significant volume-loading and transfusion requirement that is often necessary to achieve adequate flows postoperatively. Overall, approximately 20% of HeartMate II BTT patients had persistent right ventricular failure (RVF) requiring either a subsequent RVAD (6%) or intravenous inotropic support for >14 days (14%), and these patients had significantly worsened 6 month survival compared to those without RVF (71% vs. 89%, P<0.001).¹⁸⁹ Typically, mechanical right-ventricular support is temporary with intent to wean the device, and isolated right-ventricular assist devices are unusual.

Biventricular support is most commonly indicated for acute cardiogenic shock after an MI or postcardiotomy heart failure. Biventricular support is temporary, although some patients may be successfully bridged to transplant or permanent left-sided assist devices. There is currently no destination therapy device for biventricular failure.

Total Artificial Heart

The total artificial heart (TAH, SynCardia Systems, Tucson, AZ) is currently indicated as a bridge to transplant for patients in biventricular failure, particularly for those who are critically ill and too large for extracorporeal BiVAD support. Unlike ventricular assist devices, the TAH replaces the entire heart. The ventricles of the TAH are implanted orthotopically to the atrial cuffs on the ventricular side of the AV groove, and the outflow conduits are attached to the great vessels. This approach has the benefit of obviating the hemodynamic influence of pulmonary hypertension, right heart failure, myocardial or valvular problems, cardiac arrhythmias, and inotropic agents.¹⁹⁰ While this device has failed to reach its potential as a replacement for cardiac transplantation, the TAH has achieved favorable results as a BTT with a >70% survival in selected centers.^191,192,193 However, at most centers results with the TAH have been suboptimal, and it is not frequently used.

The success of catheter-based ablation and implantable cardioverter defibrillators (ICDs) has significantly diminished referrals for the surgical treatment of arrhythmias such as ventricular tachycardia, Wolff-Parkinson-White syndrome, atrial flutter, and atrioventricular nodal reentry. On the other hand, the introduction of surgical ablation modalities such as radiofrequency and cryothermal energy, has simplified the surgical treatment of atrial fibrillation (AF) and has led to a dramatic increase the in the number of surgical procedures performed annually for AF.¹⁹⁴

Atrial Fibrillation

Epidemiology of Atrial Fibrillation

Atrial fibrillation remains the most common arrhythmia in the world with an overall incidence of 0.4% to 1% that increases to 8% in those older than 80 years old.¹⁹⁵ The most serious complication of AF is thromboembolism with resultant stroke,¹⁹⁶ but serious morbidity and mortality may also result from hemodynamic compromise due to loss of atrial contraction, exacerbations of congestive heart failure from atrioventricular asynchrony and tachycardia-induced cardiomyopathy.

Medical Management

Most patients are treated medically, but the shortcomings of pharmacological management have left an important role for interventional therapies. Antiarrhythmic medications have been limited by modest efficacies and significant proarrhythmic and systemic toxicities.¹⁹⁷ Conversely, rate control strategies leave the patient in AF, do not address the impaired hemodynamics or symptoms associated with this arrhythmia, and may render subsequent attempts at rhythm control therapies less effective for younger patients that may suffer irreversible cardiac remodeling due to the prolonged period of time in AF.

Restoration of normal sinus rhythm has several potential benefits over other strategies ^198,199,200. These include improvements in atrial systolic function, which improves cardiac output and often improves symptoms in patients with congestive heart failure; a lower risk of stroke; possible discontinuation of anticoagulation; and the benefit of potentially reversing atrial structural and/or electrical remodeling.

Indications for Surgical Management

Recent consensus guidelines published by the Heart Rhythm Society state that surgical ablation for atrial fibrillation is indicated for: (a) all symptomatic AF patients undergoing other cardiac surgery; (b) selected asymptomatic AF patients undergoing cardiac surgery in which the ablation can be performed with minimal additional risk; and (c) symptomatic patients with lone AF who have failed medical therapy and prefer a surgical approach, have failed one or more attempts at catheter ablation, or are poor candidates for catheter ablation.¹⁹⁵ At our institution, relative indications for surgical ablation in patients with permanent AF that were not included in the consensus statement are: (a) a contraindication to long term anticoagulation for patients at high risk for stroke (CHADS2 score ≥ 2) and (b) a history of stroke while on therapeutic anticoagulation.

The Cox-Maze IV Procedure

The first successful operation for atrial fibrillation, the Cox-Maze procedure, was introduced clinically in 1987 by James Cox. The procedure involved the completion of a maze-like pattern of surgical incisions across both the right and left atrial that were designed to interrupt the multiple macroreentrant circuits that were thought to be responsible for AF, while still allowing propagation of the sinus impulse, restoring atrioventricular synchrony, and preserving atrial transport function. While effective at eliminating AF and reducing the risk of thromboembolism, it was not widely performed due to the fact that it was technically difficult and significantly prolonged time on cardiopulmonary bypass. In 2002, the Cox-Maze IV, was introduced. The Cox-Maze IV uses a combination of bipolar radiofrequency (RF) ablation and cryoablation to effectively replace the majority of incisions that comprise the Cox-Maze III while significantly shortening cross-clamp time and reducing operative complexity.

The Cox-Maze IV is performed on cardiopulmonary bypass through either a median sternotomy, often in combination with other cardiac surgery, or a right minithoracotomy.²⁰¹ In most cases, the right atrial lesion set is performed on the beating heart, whereas the left atrial lesions are performed during cardioplegic arrest (Fig. 21-14).

Results from the Cox-Maze IV procedure have been excellent. A recent, prospective analysis of 100 consecutive lone Cox-Maze IV patients demonstrated postoperative freedom from AF of 93%, 90%, and 90% at 6, 12, and 24 months, respectively, and freedom from AF off antiarrhythmic drugs was 82%, 82%, and 84% at the same intervals.²⁰¹ Outcomes are comparable when patients undergo concomitant cardiac surgery,²⁰² and a propensity analysis has shown that results are similar between the traditional “cut-and-sew” maze and the Cox-Maze IV.²⁰³ This procedure is often successful in patients who are poor candidates for catheter-based ablation, such as those with large left atria and patients with long-standing persistent AF.

The combination of surgical excision of the LAA and restoration of normal sinus rhythm after the Cox-Maze procedure significantly reduces stroke risk. It is our practice to stop warfarin at 3 months postoperatively in patients who are in normal sinus rhythm and without another indication for anticoagulation, regardless of CHADS2 score. With this approach, the stroke rate following the Cox-Maze procedure off anticoagulation has been remarkably low (annual risk = 0.2%).²⁰⁴ In contrast, in one report the annual rate of intracranial hemorrhage in anticoagulated patients with AF was 0.9% per year, and the overall rate of major bleeding complications was 2.3% per year.²⁰⁵

Left Atrial Lesion Sets

Some surgeons perform more limited ablation procedures, such as isolated pulmonary vein isolation or lesion sets that are limited to the left side of the heart. This is done in order to further reduce the complexity of the procedure and takes advantage of the fact that in most patients AF originates from the pulmonary veins and posterior left atrium. Although, there is seldom justification for limited lesion sets in experienced hands.

While there is a high degree of variability in both the techniques and energy sources that have been attempted for left-sided atrial lesion sets, these procedures have all incorporated some subset of the left atrial lesion set of the Cox-Maze procedure. Pulmonary vein isolation is ubiquitously performed, and the LAA is often excised. Results differ greatly between series, but a meta-analysis of the published literature by Ad and colleagues revealed that a biatrial lesion set resulted in a significantly higher late freedom from AF compared with a left atrial lesion set alone (87% vs. 73%, P = 0.05).²⁰⁶ These results are not surprising, as our intraoperative mapping experience with such patients showed a distinct region of stable dominant frequency in the left atrium only 30% of the time.²⁰⁷ The dominant frequency was located in the right atrium 12% of the time and moved during the recording period in almost half of all patients. It must also be kept in mind that recurrent right atrial flutter is a known complication of performing only the left atrial lesions. When it does occur, atrial flutter can be treated with catheter-based ablation; however, recurrent left atrial flutter can be very difficult to ablate.

Pulmonary Vein Isolation

Pulmonary vein isolation (PVI) is an attractive therapeutic option due to the fact that it can be performed off of cardiopulmonary bypass (CPB) through small or thoracoscopic incisions. The results of PVI have been variable and highly dependent on patient selection since outcomes are consistently worse in patients with longstanding persistent AF. In a study from Edgerton et al, only 56% of patients were free from AF at 6 months (35% off antiarrhythmic drugs), and with concomitant procedures, the success rate of PVI has been even lower.²⁰⁸ Several devices are available to close the LAA at the time of PVI. These include staplers and epicardial clips that can be placed without the need for CPB.

While surgical PVI has had poorer results than a Cox-Maze procedure, it has had superior results to catheter-based PVI. The Atrial Fibrillation Catheter Ablation Versus Surgical Ablation Treatment (FAST) Trial, which was a two center, randomized clinical trial, compared catheter-based ablation to thoracoscopic PVI in patients with antiarrhythmic drug-refractory AF and either left atrial dilatation and hypertension or failed prior catheter-ablation.²⁰⁹ This study demonstrated that the 12-month freedom from AF and antiarrhythmic drugs was 37% for the catheter ablation group and 66% for the PVI group (P = 0.0022).

Acute Pericarditis

Pericarditis is characterized by infiltration of the cellular and fibrous pericardium by inflammatory cells. The exact incidence and prevalence of pericarditis is unknown, but it is estimated that pericarditis is found in approximately 1% of autopsies and accounts for up to 5% of presentations of nonischemic chest pain.^210,211 The etiologies of acute pericarditis are diverse and may result from primary pericardial disorders or occur secondary to a systemic illness.²¹² In developed countries, 80% to 90% of cases are now considered idiopathic or related to a viral pathogen, but nonviral infection, autoimmune diseases, myocardial infarction, radiation, malignancy, endocrinopathy, myocarditis, aortic dissection, uremia, trauma, pharmacological side effects, and previous cardiothoracic surgery must be included in the differential diagnosis. The relative incidences of peri-infarction pericarditis, which was once common, and postcardiac injury syndrome have been dramatically reduced with the advent of thrombolytics and coronary angioplasty.²¹²

Clinical Presentation and Diagnosis

Diagnosis of acute pericarditis typically requires the identification of at least two of four cardinal features (Table 21-16). The presentation may be confused with several more common cardiopulmonary conditions, particularly myocardial infarction, making a careful history and physical critical. Patients with pericarditis classically complain of sudden onset, retrosternal pain that may be pleuritic in nature. The pain may also be positional, with alleviation of pain when the patient is upright and leaning forward. Pain from pericarditis is typically sharp or stabbing, as opposed to the dull pain or pressure that is common with angina, and it typically does not crescendo. While both conditions cause pain that often radiates to the neck, arms, and shoulders, pericarditis pain may uniquely radiate to the trapezius ridge due to innervation from the phrenic nerve.^213,214

The presence of a pericardial friction rub is pathognomonic for pericarditis, but it tends to vary in intensity over time and may be absent in 15% to 65% of patients.^213,215 As such, the sensitivity of this physical finding is dependent on the frequency and quality of auscultation. A pericardial friction rub is best heard at the left lower sternal border and is typically described as a high-pitched scratchy or squeaky sound with a triphasic cadence corresponding to the movement of the heart during atrial systole, ventricular systole, and early ventricular diastole. However, it may be monophasic or biphasic in up to 50% of patients.

Electrocardiogram (EKG) changes typically progress through four stages representing global subepicardial myocarditis and subsequent recovery. Pericarditis patients may have concave ST deflections with diffuse changes, spanning the leads of multiple coronary artery distributions, but ST segment abnormalities are absent in 20% to 40% of patients.^216,217 Acute pericarditis should not result in the development of infarct patterns, such as Q-waves or loss of R-waves, and T-wave inversions from pericarditis tend to result later in the disease process after the ST segment has returned to baseline.

Echocardiography is routinely performed in the evaluation of acute pericarditis. Its role is primarily to assess for a pericardial effusion.Although, in a patient who can be demonstrated to have previously had normal cardiac function, it may be used to exclude segmental wall motion abnormalities that may suggest ischemia.

The remaining work-up should attempt to determine the underlying cause of the pericarditis and should be directed by the history and physical. Most inflammatory markers and laboratory tests are nonspecific, but C-reactive protein (CRP) may be useful in predicting recurrence risks and in guiding the duration of anti-inflammatory medications.²¹⁸ Rarely, other imaging modalities, such as CT scanning, pericardial biopsies, or pericardiocentesis may aid in diagnosis.

Treatment

The preferred treatment depends on the underlying cause of the pericarditis. The disease usually follows a self-limited and benign course and can be successfully treated with a short course of nonsteroidal anti-inflammatory agents (NSAIDs). Some patients may require judicious use of steroids or IV antibiotics. In cases of purulent pyogenic pericarditis, surgical exploration and drainage are occasionally necessary. Rarely, accumulation of fluid in the pericardium may lead to tamponade, requiring prompt evacuation of the pericardial space. While pericardiocentesis will typically suffice, surgical drainage may be required for thick, viscous, or clotted fluid or in patients with significant scarring from previous surgeries. More commonly, surgical intervention is required to manage recurrent disease.

Relapsing Pericarditis

As many as one-third of patients with acute pericarditis will develop at least one episode of relapse.²¹² While many of these patients can be treated medically during their initial relapse and do not experience further episodes, a subset of patients experience chronic relapsing pericarditis that can significantly impact their quality of life. Recurrence may develop either from the original etiology or from an autoimmune process that occurs as a consequence of damage from the initial episode. Relapsing pericarditis normally responds to a longer course of NSAIDS ± colchicine. While steroids may induce rapid symptomatic response, their use should be limited to patients who have multiple relapses and are unresponsive to first-line agents, as several studies have suggested that steroid administration may favor relapse.²¹⁹

Pericardiectomy may be considered a last resort treatment in patients with relapsing pericarditis who are severely symptomatic despite optimal medical management, are unable to tolerate steroids or have recurrence with tamponade. Evidence for this approach is lacking, as few studies have described pericardiectomy in this population.^220,221,222 The largest study and the only one to compare surgical treatment with medical management for patients with persistent relapsing pericarditis was a report of 184 patients from the Mayo Clinic.²²¹ About 58 patients were identified as having undergone a pericardiectomy after failed medical treatment, whereas the remainder were treated with medical management only. Compared to medical treatment only, pericardiectomy resulted in significantly fewer relapses (8.6% vs. 28.6%, P = 0.009) at long term follow-up, as well as a nonsignificant trend towards less medication and corticosteroid usage. Of note, 80% of patients in the pericardiectomy group who had relapses reported significant improvements in their symptoms and had fewer relapses than before pericardiectomy. No perioperative deaths were observed, and only 2 patients (3%) had major complications. Hence, at experienced centers pericardiectomy may be a safe and viable option in select patients with relapsing pericarditis.

Chronic Constrictive Pericarditis

Etiology, Pathology, and Pathophysiology

Constrictive pericarditis can occur after any pericardial disease process but remains a rare outcome of recurrent pericarditis. It results when chronic pericardial scarring and fibrosis cause adhesion of the visceral and parietal layers and resultant obliteration of the pericardial space. While the pericardium is often grossly thickened with either focal or diffuse calcification in chronic disease, constriction may occur with normal pericardial thickness in approximately 20% of cases.^212,223 In developed nations, idiopathic causes and cardiac surgery (accounting for almost 40% of cases in some series) are the predominant underlying etiologies, followed by mediastinal radiation, pyogenic infections (i.e., Staphylococcus), and other miscellaneous causes. Tuberculosis is an additional common cause in immunosuppressed patients and in developing or underdeveloped countries.

Clinically, pericardial constriction limits diastolic filling of the ventricles and mimics right heart failure since the right-sided chambers are more affected by a rise in filling pressures. Subsequent increases in central venous pressure result in the progressive development of hepatomegaly, ascites, peripheral edema, abdominal pain, dyspnea on exertion, anorexia, and nausea (in part due to hepatic and bowel congestion). In many patients, these symptoms develop insidiously over a course of years. Since many of these symptoms are similar to those seen in patients with restrictive cardiomyopathy, the distinction between the two entities is difficult, but it remains critical because the treatment is completely different for restriction. The primary difference is that restrictive cardiomyopathy is defined by a nondilated ventricle with a rigid myocardium that causes a significant decrease in myocardial compliance, which is not seen in constrictive pericarditis.

Clinical and Diagnostic Findings

Classic physical exam findings include jugular venous distention with Kussmaul’s sign, diminished cardiac apical impulses, peripheral edema, ascites, pulsatile liver, a pericardial knock, and, in advanced disease, signs of liver dysfunction, such as jaundice or cachexia. The “pericardial knock” is an early diastolic sound that reflects a sudden impediment to ventricular filling, similar to an S3 but of higher pitch.

Several findings are characteristic on noninvasive and invasive testing. CVP is often elevated 15 to 20 mm Hg or higher. EKG commonly demonstrates nonspecific low voltage QRS complexes and isolated repolarization abnormalities. Chest X-ray may demonstrate calcification of the pericardium, which is highly suggestive of constrictive pericarditis in patients with heart failure, but this is present in only 25% of cases.²¹⁹ Cardiac CT or MRI (cMRI) typically demonstrate increased pericardial thickness (>4 mm) and calcification, dilation of the inferior vena cava, deformed ventricular contours, and flattening or leftward shift of the ventricular septum. Pericardial adhesions may also be seen on tagged cine MRI studies.

As discussed, it is most important to distinguish pericardial constriction from restrictive cardiomyopathy, which is best done with either echocardiography or right heart catheterization. Findings favoring constriction on echocardiography include respiratory variation of ventricular septal motion and mitral inflow velocity, preserved or increased mitral annulus early diastolic filling velocity, and increased hepatic vein flow reversal with expiration.^212,219 Cardiac catheterization will show increased atrial pressures, equalization of end-diastolic pressure and early ventricular diastolic filling with a subsequent plateau, called the “square-root sign.” Additional findings upon catheterization that would favor constriction include respiratory variation in ventricular filling and increased ventricular interdependence, manifest as a discordant change in the total area of the LV and RV systolic pressure curve with respiration.

Surgical Treatment

Transient constrictive pericarditis may occur weeks to months after an initial injury and follows a self-limiting course of weeks to a few months. These patients are best treated with medical therapy alone. They often lack calcification of their pericardium, and the degree of late gadolinium enhancement of the pericardium on cardiac MRI has shown promise in predicting which patients may have resolution of the process.²²⁴ Still, there is no ideal way to distinguish these patients from those who will develop chronic constrictive pericarditis, which is permanent. Therefore, if a newly diagnosed patient is hemodynamically stable, it is recommended that conservative management is attempted for two to three months prior to performing a pericardiectomy.²²³ Surgical therapy should not be delayed indefinitely, however, as results are improved when the operation is performed earlier in the course of the disease. Additional factors that predict adverse long-term outcomes include older age and prior ionizing radiation, as well as cardiopulmonary and renal dysfunction.²¹⁹ Surgery should therefore be approached cautiously in patients with very advanced, “end-stage” constrictive pericarditis, patients with mixed constrictive-restrictive disease (often from radiation), and those with significant myocardial or renal dysfunction, as those patients are at increased risk from surgery and may not experience improvement of symptoms.

In order to minimize recurrence following pericardiectomy, complete pericardial resection is desirable. This is typically performed through either a median sternotomy or left anterolateral thoracotomy while on cardiopulmonary bypass. Radical pericardiectomy involves wide resection of the constricting pericardium from the anterior surface of the heart between the phrenic nerves and the diaphragmatic surface. Decortication of the right atrium and vena cavae is not universally performed, but doing so improves the risk of persistent disease or relapse.^225,226

The extent of myocardial involvement may also affect long-term outcomes, and, thus, the depth of decortication is an important consideration.²²⁵ Even when an adequate pericardiectomy is performed, epicardial sclerosis can cause persistent hemodynamic instability or a delayed response to surgery. Sclerotic epicardium is often thin and nearly transparent, but in cases of severe chronic constrictive pericarditis it can be difficult to remove it without injury to the heart.

Surgical Results

While most patients experience significant improvement in their symptoms following pericardiectomy, symptomatic relief may take several months. Since there is a significant perioperative morbidity and mortality, pericardiectomy is best performed by experienced surgeons at high-volume centers. Between 1970 and 1985, the operative mortality was reported to be 12%, but a lower mortality of approximately 4% to 8% was noted between 1977 and 2006 at several experienced centers.^{223,226,227,228,229,230}

Long-term survival is in part determined by etiology of the disease. In a report from the Cleveland Clinic, seven-year survival rates following pericardiectomy for idiopathic, postsurgical, and radiation-induced constrictive pericarditis were 88%, 66%, and 27%, respectively.²²⁷ Results are worst for radiation-induced disease because ionizing radiation is often associated with myocardial injury as well as pericardial disease.

Despite the risks, many patients experience significant benefits from surgical treatment. In one large series, 83% of patients were reported to be free of symptoms at last follow-up.²³⁰ This is in agreement with other studies that have shown a significant improvement in NYHA functional status from class III/IV preoperatively to class I/II following pericardiectomy in >95% of patients.^{226,228,229,230}

Overview and General Clinical Features

Cardiac neoplasms are rare, with an incidence ranging from 0.001% to 0.3% in autopsy studies and a 0.15% incidence in major echocardiographic series.^231,232 Benign cardiac tumors are most common and account for 75% of primary neoplasms. Approximately 50% of benign cardiac tumors are myxomas, with the remainder being papillary fibroelastomas, lipomas, rhabdomyomas, fibromas, hemangiomas, teratomas, lymphangiomas, and others, in order of decreasing frequency. Most malignant primary cardiac tumors are sarcomas (angiosarcoma, rhabdomyosarcoma, fibrosarcoma, leiomyosarcoma, and liposarcoma), with a small incidence of malignant lymphomas. Metastatic cardiac tumors, while still infrequent, have been reported to occur 100-fold more often than primary lesions.

Clinical Presentation

The clinical presentation of cardiac neoplasms varies greatly depending on the location of the tumor, as well as its size, rate of growth, invasiveness, and friability. While as many as 10% of patients are asymptomatic, most manifest some combination of symptoms from the classic triad resulting from blood flow obstruction, tumor embolization, and constitutional symptoms.^233,234 Systemic manifestations of disease include fever, myalgias, chills, night sweats, weight loss, and fatigue and occur in up to one-third of patients.

Obstruction of cardiac blood flow accounts for the majority of presenting symptoms.²³⁴ When the tumor is located in the left atrium, symptoms tend to mimic mitral valve disease with dyspnea and pulmonary edema; although more severe presentations with syncopal episodes, hypotension, and sudden cardiac death have been reported from temporary valve orifice occlusion. When the tumor is located in the right atrium, symptoms may mimic right heart failure and include hepatomegaly, ascites, and peripheral edema. Outflow tract obstruction is rare but may be caused by large ventricular tumors.²³⁵

Tumor lysis and embolization may also lead to neurologic presentations such as stroke, retinal artery occlusion, or cerebral aneurysms, particularly in the case of pedunculated tumors and those with frond-like projections.²³⁶ Embolic tumor cells are able to lodge and penetrate distant vessel walls via subintimal growth, which leads to weakening of the arterial wall and subsequent aneurysm formation. This has been documented as late as five years out from successful primary myxoma resection.²³⁷ Alternatively, embolic implants may metastasize and create space occupying lesions. While rare, myxomatous tumor emboli have also been identified in the coronary arteries, common iliac and femoral arteries, kidney, spleen, pancreas, and liver.²³⁶

Certain clinical features may be helpful in distinguishing benign from malignant primary cardiac tumors²³⁴ Malignant tumors, primarily sarcomas, do not demonstrate a gender preference and tend to present after the fourth decade of life. They are often multifocal within the right atrium, and intramyocardial invasion can lead to refractory congestive heart failure, arrhythmias, hemopericardium, and ischemia. Conversely, benign tumors, primarily myxomas, are typically unifocal in the left atrium, have a 3:1 female preference, and occur in younger patients. Arrhythmias and pericardial effusions are very rare in this population.

Diagnosis and Characterization of Cardiac Masses

Transthoracic echocardiography is the mainstay imaging technique for the detection of cardiac tumors.²³⁴ However, echocardiography is limited by dependence on an acoustic window, suboptimal visualization of extracardiac extension, and poor soft-tissue visualization. Transesophageal echocardiography is generally only beneficial for small localized tumors due to its limited field of view. Cardiac MRI is therefore the current standard for delineating the anatomical extent of the tumor and assessing the paracardiac space and great vessels. Advantages of cMRI over CT scans include better soft-tissue evaluation without the need for iodinated contrast and no exposure to ionizing radiation.

It is important in the initial workup to distinguish a cardiac tumor from an intracardiac thrombus, which may be common in the atria of patients with AF and can mimic echocardiographic features of atrial myxomas. This determination is critical, as an atrial thrombus may be expected to resolve with anticoagulation, whereas a tumor requires surgical intervention. Moreover, anticoagulation can potentially increase the risk of peripheral embolization in patients with cardiac tumors. Delayed enhancement cMRI is the best modality to separate these two entities.cMRI may show vascularization, areas of necrosis, hemorrhage, or calcification in cardiac tumors that are not present in thrombi.

Myxoma

Pathology and Genetics

Cardiac myxomas are the most common cardiac tumor and are characterized by several distinguishing features. About 75% of the time, they arise from the interatrial septum near the fossa ovalis in the left atrium.²³⁸ Most others will develop in the right atrium, but, less commonly, they can arise from valvular surfaces and the walls of other cardiac chambers. Macroscopically, these tumors are pedunculated with a gelatinous consistency, and the surface may be smooth (65%), villous, or friable.²³³ Size varies greatly with these tumors and ranges from 1 to 15 cm in diameter. Internally, myxomas are heterogeneous and often contain hemorrhage, cysts, necrosis, or calcification. Histologically, these tumors contain cells that arise from a multipotent mesenchyme and are contained within a mucopolysaccharide stroma.²³⁹

While the majority of myxomas occur spontaneously with the highest incidence in women aged 40 to 60 years old, approximately 7% of cases are familial as part of Carney complex.²³³ Carney complex is an autosomal dominant disorder characterized by two or more of the following conditions: atrial and extracardiac myxomas, schwannomas, cutaneous lentiginosis, spotty pigmentation, myxoid fibroadenomas of the breast, endocrine overactivity (pituitary adenomas or primary adrenal hyperplasia with Cushing’s syndrome), and testicular tumors. Compared to sporadic myxomas, those that occur as part of Carney complex are more commonly found in the right atrium (37% vs. 18%) or one of the ventricles (25% vs. 0%), more often multicentric (33% vs. 6%) and more likely to recur (20% vs. 3%).²³⁸ They also present earlier at an average age of 24 years old (range 4–48 years).

Pathophysiology

Larger tumors are more likely to be associated with cardiovascular symptoms from obstruction, and embolic symptoms tend to occur from organized thrombi present on friable or villous tumors (Fig. 21-15). The relative frequencies of symptoms was illustrated by a series of 112 patients who reported cardiovascular symptoms (67%), most commonly resembling mitral valve obstruction; systemic embolization (29%); neurologic deficits (20%); and constitutional symptoms (34%).²³³ Similar incidences of symptoms have been reported in other large studies.

Treatment

Cardiac myxomas should be promptly excised after diagnosis due to the significant risk of embolization and cardiovascular complications, including sudden death. Resection may be performed through either a median sternotomy or a minimally invasive right thoracotomy while on cardiopulmonary bypass. Care is taken not to manipulate the tumor before cross clamping of the aorta in order to avoid embolization. Left atrial tumors may be approached through a standard left atriotomy.²⁴⁰ Exposure of large tumors attached to the interatrial septum may be facilitated by an additional parallel incision in the right atrium, but this is rarely necessary. An ideal resection encompasses both the tumor and a portion of the cardiac wall or interatrial septum to which it is attached. In order to prevent recurrence, a full thickness excision of the attachment site is preferred, but partial thickness excisions and cryoablation of the base have been performed with good late results.²⁴⁰ The defect created in the atrial septum can either be repaired primarily or with a small patch. Finally, patients with valvular involvement may require additional valvular reconstruction or replacement, and rare cases of cardiac autotransplantation (with atrial reconstruction) or transplantation have been reported as strategies for complex cases of recurrent atrial myxoma.^241,242

Short- and long-term results following excision are excellent for benign cardiac myxomas. Operative mortality is low, and the probability of disease-free survival at 20 years has been reported to be as high as 92% for benign, sporadic myxomas.^233,240 Risk of recurrence is significantly higher for familial cases.

Other Benign Cardiac Tumors

There are several benign cardiac tumors apart from myxomas that are infrequent but have distinct pathophysiologic features.²³⁴ Papillary fibroelastomas are the second most common primary cardiac tumor, representing approximately 8% of all cases. These tumors typically occur in more elderly patients; are small (<1 cm in diameter) sessile, pedunculated masses that arise from the mitral or aortic valves; and frequently result in embolization. Fibroelastomas can almost always be resected with preservation of the native valve leaflets, and cryoablation of the valve leaflet after resection can help prevent recurrence. Lipomas are encapsulated tumors that usually arise from the epicardium and remain asymptomatic in most patients. Hemangiomas, which may arise from any cardiac structure, including the pericardium, account for 2% of benign cardiac tumors, and atrioventricular node tumors, which often lead to sudden cardiac death from heart block and ventricular fibrillation, are exceedingly rare.

In children, rhabdomyomas are the most common primary cardiac tumor, whereas fibromas are the most commonly resected cardiac tumor. Rhabdomyomas are myocardial hamartomas that are often multicentric in the ventricles. About 50% of cases are associated with tuberous sclerosis, and while resection is occasionally necessary, most disappear spontaneously. Fibromas are congenital lesions that one-third of the time are found in children younger than one-year old. These tumors, conversely, are ordinarily solitary lesions found in the inner interventricular septum, and they may present with heart failure, cyanosis, arrhythmias, syncopal episodes, chest pain, or sudden cardiac death.

Malignant Cardiac Tumors

Primary cardiac malignancies are very rare, but when they occur they tend to have a right-sided predominance and frequently demonstrate extracardiac extension and involvement.^234,243 Malignant cardiac tumors include angiosarcoma, osteosarcoma, leiomyosarcoma, rhabdomyosarcoma, liposarcoma, and primary cardiac lymphomas. Angiosarcomas are aggressive, rapidly invading adjacent structures, and 47% to 89% of patients present with lung, liver, or brain metastases by the time of diagnosis. Leiomyosarcomas are sessile masses with a mucous appearance that are typically found in the posterior wall of the left atrium. Rhabdomyosarcomas are bulky (>10 cm in diameter) tumors that usually occur in children and do not have a predilection for any particular chamber. They frequently invade nearby cardiac structures and are multicentric in 60% of cases. Finally, while not as frequent as secondary cardiac lymphomas, primary cardiac lymphomas are increasing in frequency due to lymphoproliferative disorders caused by Epstein-Barr virus in immunosuppressed patients. The absence of necrotic foci in lymphomas can be used to differentiate these tumors from cardiac sarcomas.

Metastatic Cardiac Tumors

Cardiac metastases have been found in approximately 10% of autopsies performed for malignant disease.²³⁴ Secondary cardiac tumors, unlike primary tumors, are therefore relatively common. They may arise from direct extension of mediastinal tumors, hematological spread, intracavitary extension from the inferior vena cava or lymphatic extension, although the latter is the most common mechanism.

While they can occur with most any primary tumor, they are generally observed late in the course of disease. Malignant melanomas have a high potential for cardiac involvement, but other soft tissue tumors such as lung cancer, breast cancer, sarcomas, renal carcinoma, esophageal cancer, hepatocellular carcinoma, and thyroid cancer may all progress to cardiac involvement. Cardiac metastases may also develop from leukemia and lymphoma in 25% to 40% of cases.²⁴⁴

Metastatic cardiac tumors are typically found in random locations, excluding the valvular tissue where lymphatics are absent, and they may be multifocal or diffusely extend along the epicardial surface. Signs of malignant cardiac involvement in cancer patients include pericardial effusion or tamponade, tachyarrhythmias, and heart failure symptoms. Workup is similar to other cardiac tumors. Treatment is generally with combined chemotherapy and radiation and is rarely effective.