Chapter 19.II: Congenital Heart Disease

Congenital heart disease encompasses a wide range of anomalies that result from abnormal fetal development of the heart. Defects can range from simple to complex. The age of presentation of these defects depends primarily on the physiologic impact of the anomaly. After birth, patients can present within minutes to hours with profound hypoxemia or hemodynamic collapse. Others may present weeks to months later with evidence of a new murmur or signs of congestive heart failure. Relatively asymptomatic lesions can go undetected until children are school age or adolescents. With current ultrasound imaging, many cardiac anomalies are identified on prenatal examination.

Early and accurate diagnosis of congenital heart disease requires careful identification of signs and symptoms of heart disease. The initial workup begins with a focused history and physical examination. Classification of heart murmurs can be highly suggestive of underlying cardiac anomalies. Early signs of heart disease include cyanosis, tachypnea, unequal pulses, and failure to thrive. Key symptoms of congenital heart disease in the patient’s history include feeding difficulties, irritability, and frequent respiratory infections.

Standard diagnostic studies include a chest radiograph (CXR) and electrocardiography (EKG). Some cardiac defects have pathognomonic findings on CXR. Other anomalies may be suspected based on heart size, increased or decreased pulmonary markings, aortic arch sidedness, or situs abnormalities (the heart located in the mid- or right chest rather than the typical location in the left chest). EKG can identify rhythm disturbances, axis deviation, atrial enlargement, and ventricular hypertrophy. Transthoracic echocardiography is often the only diagnostic test needed to provide the anatomic detail required for surgical planning. Cardiac catheterization, cardiac magnetic resonance imaging (cMRI), and computed tomography angiography (CTA) are used as adjunct diagnostic tests when additional information on flow, pressure, resistance, or anatomic detail is required.

The care of congenital heart disease patients requires a collaborative effort of a multidisciplinary team of cardiologists, surgeons, interventionalists, echocardiographers, and radiologists. For the majority of congenital heart defects, surgical correction or catheter-based intervention is necessary for definitive treatment. Careful timing and planning of operative and catheter-based interventions along with highly skilled preoperative and postoperative care are essential to a successful outcome.

Certain defects such as atrial septal defects (ASDs), ventricular septal defects (VSDs), and patent ductus arteriosus (PDA) may resolve spontaneously over the first several years of life. The remaining defects require intervention when the risk of surgery is reasonable, when symptoms can no longer be managed medically, and/or prior to the onset of irreversible complications.

Neonates presenting with ductal-dependent lesions require ductal blood flow to maintain systemic or pulmonary perfusion. Ductal patency is achieved with intravenous prostaglandin E₁ therapy. Supplemental oxygen is supplied only as necessary for cyanosis as newborns tolerate relative cyanosis (oxygen saturations > 70%) quite well. The remainder of therapy is directed toward managing congestive heart failure symptoms with diuretics, afterload reduction, and maximal caloric intake.

For most congenital heart defects, surgical correction is possible. For more complex defects, staged repair with early palliation as well as staged palliation remain options. The anticipated somatic growth of the child must be considered when determining the surgical approach. Invasive monitoring lines are essential for monitoring patients during surgery and postoperatively. All patients have arterial and central venous catheters placed along with peripheral intravenous catheters and a Foley catheter. For neonates, the umbilical vessels are the desired venous and arterial access. Avoidance of long-standing and repeated femoral lines is important because patency of these vessels is often essential for diagnostic and interventional catheter procedures later in life. Due to variable blood flow with perfusion techniques and underlying cardiac anomalies, it is possible to have differential cooling and rewarming. Therefore, temperature probes are placed in the nasopharynx, the rectum, and on the skin to allow for accurate monitoring.

Most surgical repairs require cardiopulmonary bypass. This involves drainage of venous blood from the patient via cannulae placed in the superior and inferior vena cava (for intracardiac repairs) or a single cannula in the right atrium. Blood passes through the bypass circuit, which warms or cools the blood to the desired temperature, adds oxygen and removes carbon dioxide, and pumps the blood back into the body via an arterial cannula, usually in the ascending aorta. Hypothermia may be employed to decrease the metabolic demands of the body and heart, which provides additional protection against ischemia. The degree of hypothermia, 18-34°C, depends on the complexity and time needed to complete the procedure. The heart can be arrested with high-potassium cardioplegic solution delivered through the coronary arteries antegrade (through a cannula proximal to an aortic cross-clamp in the aorta) or retrograde (through a cannula placed in the coronary sinus). Arresting the heart allows the surgeon to operate safely with a still and bloodless field. An additional vent can be placed via the right superior pulmonary vein to capture pulmonary venous return and to assist in deairing of the heart.

Hypothermic circulatory arrest is required for complex aortic arch reconstructions. This involves cooling the patient to 18°C for a minimum of 20 minutes to ensure even cooling of the brain and body. The head is packed in ice, the patient’s blood is drained into the venous reservoir, and the pump is turned off. The cannulae can then be removed from the field to aid in visualization and repair of the arch. No absolute safe duration of hypothermic circulatory arrest has been determined, but it is generally felt that it should be limited to no more than 45 minutes. Alternative techniques, such as regional cerebral perfusion and intermittent low-flow perfusion, have been employed to minimize the need for hypothermic circulatory arrest. To date, however, there is no literature to support that these techniques have additional benefit without additional risk.

Patients are brought to the intensive care unit intubated and mechanically ventilated. All patients have temporary pacing wires in place for management of bradyarrhythmias and tachyarrhythmias. Many patients have additional intracardiac lines in place for pulmonary artery and left atrial pressure monitoring. Drainage catheters are placed within the mediastinum to prevent accumulation of blood and fluid. These are usually removed 2-4 days following surgery. Prophylactic antibiotics are given preoperatively as well as postoperatively when drainage tubes are in place.

Cardiopulmonary bypass produces a significant inflammatory response due to activation of cytokines. Patients exhibit fluid retention and pulmonary dysfunction as a result, requiring aggressive use of diuretics and mechanical ventilation as needed. Bleeding is a common complication following cardiac surgery and infrequently requires surgical exploration (< 2%). Postoperative coagulopathy results from a multitude of factors, including hemodilution, platelet damage, factor consumption, immature hepatic production of clotting factors, and incomplete reversal of heparin with protamine sulfate. Approximately 30% of all patients will have some arrhythmia after surgery, ranging from simple premature ventricular contractions to malignant tachyarrhythmias. The risk for long-term arrhythmias requiring chronic medication or heart block requiring a permanent pacemaker is approximately 1%. Most patients require hemodynamic support with vasopressors along with afterload reduction as necessary for ventricular dysfunction. Dopamine, epinephrine, and vasopressin are the first-line vasopressors for pediatric patients. Milrinone is used primarily for afterload reduction. Critically ill neonates may have thyroid and adrenal hypofunction, which can further exacerbate postoperative hemodynamic instability. Profound hemodynamic compromise occasionally requires additional mechanical assistance. Extracorporeal membrane oxygenation (ECMO) is the most widely and acutely available mechanical support for the pediatric population. The survival for congenital heart disease patients requiring ECMO support is approximately 50%. For patients in low cardiac output state, it is essential to rule out residual defects or repair failures that could be readdressed surgically or in the catheterization laboratory.

The pediatric population has highly reactive pulmonary vasculature that is unique from the adult cardiac surgery population. Postoperative pulmonary hypertensive crises can occur in the newborn and infant population. Crises can be initiated with agitation such as endotracheal suctioning. Maneuvers to minimize and treat pulmonary hypertensive crises include high-dose opioid anesthesia with fentanyl, paralysis, respiratory alkalosis, high fraction of inspired oxygen, and inhaled nitric oxide. Chronic agents to treat persistent pulmonary hypertension include phosphodiesterase inhibitors (eg, sildenafil) and prostacyclin (eg, Flolan).

Cyanotic heart defects result from shunting of deoxygenated blood from the right side of the heart to the oxygenated left side of the heart or inadequate pulmonary blood flow. The relative mixing of deoxygenated and oxygenated blood produces desaturation of the arterial blood. The majority of cyanotic heart defects are diagnosed within the first few days to months of life. Cyanotic heart defects represent approximately 25% of all congenital heart defects.

The classic 5 T’s of cyanotic heart defects—(1) tetralogy of Fallot (TOF); (2) transposition of the great arteries (TGAs); (3) truncus arteriosus; (4) total anomalous pulmonary venous return; and (5) tricuspid atresia are presented in this chapter along with hypoplastic left heart syndrome (HLHS).

Tetralogy of Fallot

A. General Considerations

TOF is the most common cyanotic congenital heart defect. It occurs in 0.6 per 1000 live births and has a prevalence of about 4% among all patients with congenital heart disease. The pathologic anatomy is frequently described as having four components: VSD, overriding aorta, pulmonary stenosis, and right ventricular (RV) hypertrophy (Figure 19–27). Embryologically, the anatomy of TOF is thought to result from a single defect: anterior malalignment of the infundibular septum. The infundibular septum normally separates the primitive outflow tracts and fuses with the ventricular septum. Anterior malalignment of the infundibular septum creates a VSD due to failure of fusion with the ventricular septum and also displaces the aorta over the VSD and right ventricle. Infundibular malalignment also crowds the RV outflow tract, causing pulmonary stenosis and, secondarily, RV hypertrophy. Prominent muscle bands also extend from the septal insertion of the infundibular septum to the RV free wall and contribute to the obstruction of the RV outflow tract. The pulmonary valve is usually stenotic and is bicuspid in 58% of cases. Pulmonary atresia occurs in about 7% of cases. The branch pulmonary arteries in TOF may exhibit mild diffuse hypoplasia or discrete stenosis (most frequently of the left pulmonary artery at the site of ductal insertion). Coronary artery anomalies are frequently present. The origin of the left anterior descending artery from the right coronary artery, which occurs in 5% of cases, is clinically important because the vessel crosses the RV infundibulum and is vulnerable to injury at the time of surgery. A right aortic arch is present in 25% of patients. Associated defects include ASD, complete atrioventricular septal defect (AVSD), PDA, or multiple VSDs.

B. Clinical Findings

Patients with TOF develop cyanosis due to right-to-left shunting across the VSD. The degree of cyanosis depends on the severity of obstruction of the RV outflow tract. Frequently, cyanosis is mild at birth and may remain undetected for weeks or months. Neonates with severe infundibular obstruction or pulmonary atresia will develop symptoms shortly after birth and require a prostaglandin infusion to maintain ductal patency to ensure adequate pulmonary blood flow. In other patients, the RV outflow tract obstruction is minor, and the predominant physiology is that of a large VSD with left-to-right shunting and congestive heart failure.

The occurrence of intermittent cyanotic spells is a well-known feature of tetralogy. The etiology of “spelling” is still controversial but is clearly related to a transient imbalance between pulmonary and systemic blood flow. A spell may be triggered by hypovolemia or peripheral vasodilation (eg, after a bath or vigorous physical exertion). Spells may occur in neonates but are most frequently reported in infants between the ages of 3 and 18 months. Most spells resolve spontaneously within a few minutes, but some spells may be fatal. Older children have been observed to spontaneously squat to terminate spells. The squatting position is thought to increase systemic vascular resistance, which thereby favors pulmonary blood flow.

Cyanosis is the most frequent physical finding in TOF. Auscultation reveals a normal first heart sound and a single second heart sound. A systolic ejection murmur is present at the left upper sternal border. Older children may develop clubbing of the fingers and toes. Chest radiography typically demonstrates a boot-shaped heart due to elevation of the cardiac apex from RV hypertrophy. Pulmonary vascular markings are usually reduced. A right aortic arch may be present. An electrocardiogram shows RV hypertrophy. Echocardiography is definitive, and catheterization is not necessary in most cases.

C. Treatment

The medical management of TOF is directed toward the treatment and prevention of cyanotic spells. The immediate treatment of the spelling patient includes administration of oxygen, narcotics for sedation, and correction of acidosis. Transfusion is indicated for anemic infants. Alpha-agonists are useful for increasing systemic vascular resistance (which favors pulmonary blood flow). Some centers have used beta-blockers as a form of long-term therapy to suppress the incidence of spells. Long-term complications of untreated TOF include clubbing of the fingers and toes, severe dyspnea on exertion, brain abscesses (secondary to right-to-left shunting), paradoxical embolization, and polycythemia (which may lead to cerebral thrombosis). Long-term survival is unlikely for most patients with untreated TOF.

All patients with TOF should undergo surgical repair. Asymptomatic patients should be repaired electively between 4 and 6 months of age. Early repair is indicated for neonates with severe cyanosis and for infants who have had a documented spell or worsening cyanosis.

Classically, the repair of TOF was accomplished in two stages. During the first stage, pulmonary blood flow was augmented by creating a connection (or shunt) between a systemic artery and the pulmonary artery. At the second stage, the shunt was taken down, and a complete repair was performed. The first shunt procedure was the Blalock-Taussig shunt, in which the subclavian artery was mobilized and divided distally, and an end-to-side anastomosis was created between the inferiorly deflected subclavian and the ipsilateral pulmonary artery. The modified Blalock-Taussig shunt is the most common type of shunt used today and consists of an interposition graft (polytetrafluoroethylene) between the innominate or subclavian artery and the ipsilateral pulmonary artery. Creation of a shunt may be accomplished with or without the use of cardiopulmonary bypass.

Currently, one-stage repair of TOF is preferred by most centers. Initial palliation with a shunt is still indicated for some patients who present a high risk for complete repair, such as those with multiple congenital anomalies, significant prematurity, severe concurrent illness, or an anomalous coronary artery crossing a hypoplastic infundibulum.

Complete repair of TOF is performed using a median sternotomy and cardiopulmonary bypass with bicaval venous cannulation. By a transatrial approach, the RV outflow tract can be examined through the tricuspid valve. Muscle bundles obstructing the RV outflow tract are divided or resected. The VSD is closed with a patch. Pulmonary valvotomy is performed, when indicated, via a vertical incision in the main pulmonary artery. When the pulmonary valve annulus or infundibulum is severely hypoplastic, a transannular outflow tract patch may be necessary to relieve the obstruction. When an anomalous coronary artery crosses the infundibulum, a transannular incision may be contraindicated. In these cases, and in patients with pulmonary atresia, placement of a conduit (cryopreserved homograft or bioprosthetic heterograft) between the right ventricle (via a separate ventriculotomy) and main pulmonary artery will be necessary. Patients who undergo construction of a transannular patch develop pulmonary insufficiency as a consequence. This is surprisingly well tolerated in most infants, as long as the tricuspid valve is competent.

As these patients grow older, some will develop RV failure due to chronic pulmonary insufficiency, and pulmonary valve replacement may be necessary. Currently, pulmonary valve replacement is indicated for symptomatic patients or those at risk of life-threatening arrhythmias. For asymptomatic patients, it is generally agreed that pulmonary valve replacement should be undertaken before irreversible RV dysfunction occurs. cMRI has evolved as a valuable diagnostic tool for evaluating RV size, function, anatomic detail, and other hemodynamic parameters. An RV size “cutoff” is debated, but recent recommendations suggest considering valve replacement before RV end-diastolic volume index exceeds approximately 160 mL/m². Catheter-based pulmonary valve replacement is an option for some patients depending on the RV outflow tract anatomy.

D. Prognosis and Complications

The early mortality following repair of TOF is 1%-5%. The results are worse for patients with TOF and pulmonary atresia. Long-term complications include recurrent obstruction of the RV outflow tract and development of RV dysfunction due to chronic pulmonary insufficiency. Actuarial survival at 20 years is 90% with excellent functional status.

Transposition of Great Arteries

A. General Considerations

TGA is a congenital cardiac anomaly in which the aorta arises from the right ventricle and the pulmonary artery originates from the left ventricle (Figure 19–28). TGA is divided into dextro-looped (d-TGA) and levo-looped (l-TGA). The looping refers to the right or left looping of the primitive heart tube during fetal development, which determines whether the atria and ventricles are concordant (right atrium attaches to the right ventricle and left atrium attaches to the left ventricle) or discordant. l-TGA is associated with atrioventricular (AV) discordance (right atrium attaches to the left ventricle and left atrium attaches to the right ventricle) and is also termed congenitally corrected TGA. l-TGA is a rare variant of TGA and is beyond the scope of this chapter, which focuses on d-TGA. The defect can be subdivided into d-TGA with intact ventricular septum (IVS) (55%-60%) and d-TGA with VSD (40%-45%), one-third of which are hemodynamically insignificant. Pulmonic stenosis, causing significant left ventricular outflow tract obstruction, occurs rarely with an IVS and in approximately 10% of d-TGA/VSD.

B. Clinical Findings

d-TGA is a relatively common cardiac anomaly and is the most common form of congenital heart disease presenting as cyanosis in the first week of life. The malformation accounts for approximately 10% of all congenital cardiovascular malformations in infants. The degree of cyanosis depends on the amount of mixing between the pulmonary and systemic circulations. In d-TGA, oxygenated pulmonary venous blood is returned to the lungs, and desaturated systemic blood is returned to the body. Because the two circulations exist in parallel, some mixing between them must occur to allow oxygenated blood to reach the systemic circulation and the desaturated blood to reach the lungs. Mixing may occur at a number of levels, most commonly at the atrial level through an ASD or a patent foramen ovale (PFO). Generally, two levels of mixing are necessary to maintain adequate systemic oxygen delivery with a VSD or PDA serving as an additional site for cardiac mixing. In d-TGA, there can be no fixed shunt in one direction without an equal amount of blood passing in the other direction; otherwise, one circulation would eventually empty into the other. Therefore, the amount of desaturated blood reaching the lungs (effective pulmonary blood flow) must equal the amount of saturated blood reaching the aorta (effective systemic blood flow). Clinical characteristics are dependent on the degree of mixing and the amount of pulmonary blood flow. These factors relate to the specific anatomic subtype of d-TGA. Neonates with d-TGA/IVS (or small VSD) have mixing limited to the atrial level and PDA. The ASD may be restrictive, and the PDA generally will close over the first days to week of life. As the degree of mixing decreases, the patient becomes increasingly cyanotic and will eventually suffer cardiovascular collapse. Fortunately, the majority of these neonates will manifest cyanosis early in life, which is recognized by a nurse or physician within the first hour in 56% and in the first day in 92%. In d-TGA with a large VSD, there is additional opportunity for mixing and increased pulmonary blood flow. The neonate with d-TGA/VSD may manifest only mild cyanosis, which may be initially overlooked. However, generally within 2-6 weeks, signs and symptoms of congestive heart failure will emerge. Tachypnea and tachycardia become prominent, while cyanosis may remain mild. Auscultatory findings are consistent with congestive heart failure with increased pulmonary blood flow, including a pansystolic murmur, third heart sound, mid-diastolic rumble, gallop, and narrowly split second heart sound with an increased pulmonary component. Neonates with d-TGA and significant pulmonary stenosis present with severe cyanosis at birth. Lesser degrees of pulmonary stenosis will result in varying levels of cyanosis.

In cases of d-TGA, the electrocardiogram is normal at birth, demonstrating the typical pattern of RV dominance. Although the classic chest radiographic appearance of an egg-shaped heart with a narrow superior mediastinum may be seen, this finding is often obscured by an enlarged thymic shadow. The abnormal ventriculoarterial connection is clearly seen on echocardiography, which demonstrates that the posterior great vessel arising from the left ventricle is a pulmonary artery that bifurcates soon after its origin. The anterior great vessel is the aorta and arises from the RV. Associated lesions, including VSD, left ventricular outflow tract obstruction, and coarctation, may also be diagnosed. Although used less frequently for diagnosis, cardiac catheterization may be helpful to improve cardiac mixing by means of balloon atrial septostomy.

C. Treatment

The infant with d-TGA and severe cyanosis requires prompt diagnosis and treatment to improve mixing and increase the arterial oxygen saturation. The first intervention to improve mixing in a cyanotic newborn suspected of having TGA is to insure ductal patency by beginning an infusion of prostaglandin E₁. In the presence of a restrictive ASD, a balloon atrial septostomy, a technique developed by William Rashkind in 1966, is performed. The procedure involves inserting a balloon-tipped catheter across the foramen ovale into the left atrium. Inflation and forcible withdrawal of the catheter tears the septum primum and enlarges the ASD. Mixing generally increases immediately, with a substantial increase in arterial oxygen saturation. Without intervention, d-TGA is universally fatal. Untreated, 30% of neonates will die in the first week of life, 50% by the first month, 70% within 6 months, and 90% by 1 year. The definitive surgical treatment of patients with d-TGA has changed dramatically with the advent of the arterial switch operation (ASO). The ASO, first successfully performed by Jatene in 1975, has become the optimal surgical procedure for infants with this condition. Current techniques have reduced the operative mortality to 2%-4%. The operative technique involves transection of both great vessels and direct reanastomosis to reestablish ventriculoarterial concordance. Additionally, the coronary arteries are removed from the anterior aorta and relocated to the posterior great vessel (neoaorta). The extensive experience gained with this procedure has confirmed that any variant of coronary artery anatomy can be successfully repaired, although certain unusual forms impose a higher risk. Because many patients with d-TGA have an IVS, left ventricular pressure falls early in life as pulmonary vascular resistance decreases. In this situation, it is essential that the arterial repair be performed within the first 2-3 weeks of life, while the left ventricle is still able to meet systemic workloads. In patients presenting later, the left ventricle can be retrained with a preliminary pulmonary artery band and aortopulmonary shunt followed by the definitive arterial repair. Although patients with large VSDs do not require early repair because of their decreased left ventricular pressure, experience has indicated that even in this subgroup, the operation is best performed within the first month of life, before secondary complications such as pulmonary hypertension, congestive heart failure, or infection develop.

Patients with fixed left ventricular outflow tract obstruction are not candidates for the arterial repair because correction would result in systemic ventricular outflow tract obstruction. Most of these patients also have large VSDs. Palliation early in life with systemic-to-pulmonary artery shunting is an option, with definitive repair postponed until somatic growth results in cyanosis as the shunt is outgrown. At that time, the Rastelli procedure is performed, in which left ventricular blood is redirected through the VSD to the anterior aorta by placement of an intraventricular patch. The pulmonary artery is ligated, and right ventricle-to-distal pulmonary artery continuity is reestablished with a valve-bearing conduit. An increasing number of experienced centers currently recommend early complete repair in the neonatal period using a Rastelli procedure. Early repair eliminates the interim morbidity and mortality associated with a systemic-to-pulmonary artery shunt and chronic cyanosis.

D. Prognosis

Current hospital survival for the ASO is 96.6%-97.2%. Generally, dTGA/IVS has had a lower mortality than d-TGA/VSD or d-TGA/VSD/PS. Hospital mortality for d-TGA/IVS is 2.2%, compared to 4.3% for d-TGA/VSD. Long-term survivals at 5-10 years and 15-20 years are 92.2%-97.9% and 91.6%-96%, respectively. The most common cause for reintervention is supravalvar pulmonary stenosis, occurring in 19.7%-30.3%. A recent study of 40 patients undergoing a Rastelli operation over a 20-year period revealed a hospital mortality of 0%, with Kaplan–Meier survival of 93% at 5, 10, and 20 years. Freedom from conduit replacement was 86% at 5 years and 59% at 20 years.

Truncus Arteriosus

A. General Considerations

Truncus arteriosus is a rare anomaly that accounts for 0.4%-4% of all cases of congenital heart disease. A single arterial vessel arises from the heart, overriding the ventricular septum, and gives rise to the systemic, coronary, and pulmonary circulations. The Collett and Edwards classification of truncus arteriosus focuses on the origin of the pulmonary arteries from the common arterial trunk, as follows:

• Type I: Common arterial trunk gives rise to a main pulmonary artery and the aorta.

• Type II: Right and left pulmonary arteries arise directly from and in close proximity to the posterior wall of the truncus.

• Type III: Right and left pulmonary arteries arise from more widely separated orifices on the posterior truncal wall.

• Type IV: Branch pulmonary arteries are absent. Pulmo­nary blood flow is derived from aortopulmonary collaterals.

Persistent truncus arteriosus is the result of failed development of the aortopulmonary septum and subpulmonary infundibulum (conal septum). Normal septation leads to the development of both pulmonary and systemic outflow tracts, division of the semilunar valves, and formation of the aorta and pulmonary arteries. Failure of septation results in a VSD (absence of the infundibular septum), a single semilunar valve, and a single arterial trunk. Most cases are associated with a VSD with the superior margin of the defect formed by the truncal valve. The truncal valve leaflets are generally dysmorphic and their motion may be restricted. Leaflet number is highly variable, with about 65% tricuspid, 22% quadricuspid, 9% bicuspid, and rarely unicuspid or pentacuspid. As a result of these abnormally developed valve leaflets, a moderate or greater degree of truncal insufficiency is present in 20%-26% of patients. The pulmonary arteries are usually of normal size and most often arise from the left posterolateral aspect of the truncal artery, often in close proximity to the truncal valve and ostium of the left coronary artery.

Other cardiac anomalies are common and include an ASD (9%-20%), an interrupted aortic arch (10%-20%), and coronary ostial abnormalities (37%-49%) with the left coronary artery frequently noted to have a high origin, not uncommonly near the takeoff of the pulmonary arteries. Extracardiac anomalies are reported in approximately 28% of patients with truncus arteriosus. Described abnormalities include skeletal, genitourinary, gastrointestinal, and DiGeorge syndrome (11%).

B. Clinical Findings

The anatomy of truncus arteriosus results in obligatory mixing of systemic and pulmonary venous blood at the level of the VSD and truncal valve, which produces arterial saturations of 85%-90%. The systemic arterial saturation depends on the volume of pulmonary blood flow, which in turn is determined by the pulmonary vascular resistance (PVR). As the resistance begins to fall, excessive pulmonary circulation ensues and leads to pulmonary congestion and signs and symptoms of congestive heart failure. This nonrestrictive left-to-right shunt may cause early development of irreversible pulmonary vascular obstructive disease.

The presence of truncal valve abnormalities poses further hemodynamic burdens. Truncal valve regurgitation leads to ventricular dilation and low diastolic coronary perfusion pressures that can result in myocardial ischemia. Truncal valve stenosis promotes ventricular hypertrophy, increases the myocardial oxygen demand, and limits coronary and systemic perfusion, especially with the large volume of runoff into the pulmonary vascular bed.

Neonates with truncus arteriosus present with signs of congestive heart failure and collapsing peripheral pulses. Chest radiography shows marked cardiomegaly, pulmonary plethora, often with minimal thymus shadow, and a right aortic arch. The electrocardiogram most often depicts biventricular hypertrophy. Echocardiography is the diagnostic procedure of choice and can demonstrate the truncal vessel, the structure and function of the truncal valve, associated lesions such as interrupted aortic arch, and often the pulmonary arterial anatomy. Cardiac catheterization is not performed unless the anatomy is unclear, further information is needed about the status of the truncal valve, or the status of the pulmonary vasculature is unclear (ie, infants older than 3 months at diagnosis).

C. Treatment

The natural history of patients born with truncus arteriosus is early demise. Approximately 40% of infants are dead within 1 month, 70% by 3 months, and 90% by 1 year. Early death is caused by congestive heart failure. Survivors may do well for a period of time until the development of pulmonary vascular obstructive disease and Eisenmenger syndrome. The ultimate treatment of truncus arteriosus is surgical correction in the neonatal period. Medical treatment is palliative and directed toward controlling congestive heart failure with fluid restriction, diuretics, and afterload reduction. Complete repair entails separating the pulmonary arteries from the truncus, repairing the resulting defect in the aorta, closing the VSD, and restoring continuity of the RV outflow tract with an extracardiac conduit (Figure 19–29). Severe truncal valve regurgitation requires truncal valve repair or replacement. An associated interrupted aortic arch is repaired by constructing a primary end-to-end anastomosis of the distal ascending aorta with proximal augmentation if necessary.

D. Prognosis

The results of truncus arteriosus repair have improved greatly during the last two decades. Before the importance of early operation to avoid irreversible pulmonary vascular disease was appreciated, patients underwent repair at most institutions at an average age of 2-5 years with high mortality rates. Current hospital mortality for the neonatal repair of truncus arteriosus ranges between 4.3% and 17%, with the majority of deaths occurring in complex truncus arteriosus or in truncus arteriosus with associated severe truncal valve regurgitation. All patients will ultimately require reoperation for replacement of the right ventricle to pulmonary artery conduit with only 30%-42% being free from reoperation at 10 years. Thirty-year survival is approximately 75%-83%.

Total Anomalous Pulmonary Venous Connection

A. General Considerations

Total anomalous pulmonary venous connection (TAPVC) is a relatively uncommon congenital defect representing approximately 2% of all congenital heart anomalies. TAPVC encompasses a group of anomalies in which the pulmonary veins connect directly to the systemic venous circulation via persistent splanchnic connections. This abnormality results from failed transfer, in the normal developmental sequence, of pulmonary venous drainage from the splanchnic plexus to the left atrium. The most common classification system consists of four types: supracardiac (type 1), cardiac (type 2), infracardiac (type 3), and mixed (Figure 19–30). Partial anomalous pulmonary venous connection defines patients in whom some but not all venous drainage enters the left atrium, while the remaining veins connect to one or more persistent splanchnic veins.

TAPVC can also be classified by the presence of obstruction. Impingement from surrounding structures or inadequate caliber of the draining pulmonary vein(s) can result in varying degrees of obstruction. Obstruction in supracardiac TAPVC can occur by compression of the ascending vertical vein between the left main stem bronchus and left pulmonary artery or by narrowing at the insertion of the vertical vein into the innominate vein. Obstruction is always present in the infracardiac type because the pulmonary venous blood must pass through the sinusoids of the liver. Obstruction is uncommon in the cardiac type.

Supracardiac occurs in approximately 45% of patients. The common pulmonary vein drains superiorly into the innominate vein, superior vena cava, or azygous vein via an ascending vertical vein. Cardiac TAPVC occurs in approximately 25% of patients. The pulmonary venous confluence drains into the coronary sinus or, on rare occasions, individual pulmonary veins will connect directly into the right atrium. Infracardiac TAPVC occurs in approximately 25% of patients. The pulmonary venous confluence drains into a descending vertical vein through the diaphragm into the portal vein or ductus venosus. Finally, a mixed type of TAPVC occurs in approximately 5% of patients and can involve any or all components of the previous three types.

B. Clinical Findings

TAPVC produces a mixing lesion because oxygenated blood from the pulmonary system drains back into the systemic venous circulation. The size of the ASD dictates the distribution of blood flow. Most patients with unobstructed TAPVC have few or no symptoms in infancy and present with signs and symptoms similar to an ASD. In the neonate with obstructed TAPVC, venous drainage from the pulmonary vasculature is impaired, leading to pulmonary venous hypertension and pulmonary edema. In severe cases, this increased pressure will lead to reflexive vasoconstriction of the pulmonary vasculature with pulmonary hypertension. Patients with obstruction present early in life with profound cyanosis from pulmonary edema.

The diagnosis can be made with echocardiographic identification of the anomalous connection of the pulmonary venous confluence to the systemic venous system. The ASD and other associated anomalies can be delineated. Cardiac catheterization is rarely necessary unless accurate measurement of PVR is needed.

The management of TAPVC is surgical repair. In patients with obstruction, medical management for stabilization may be employed but is often unsuccessful and should not delay surgical intervention.

C. Treatment

The principle of operative repair is to establish an unobstructed communication between the pulmonary venous confluence and the left atrium, interrupt the connections with the systemic venous circulation, and close the ASD. The specific repair is dependent on the type of anomalous connection.

1. Supracardiac TAPVC The repair of supracardiac TAPVC may be performed with moderate hypothermia (28-32°C) and bicaval cannulation or with a brief period of hypothermic (18°C) circulatory arrest. The optimal approach is to retract the ascending aorta to the left and the superior vena cava to the right to expose the pulmonary venous confluence. This approach provides excellent exposure without distortion of the heart or venous structures. The vertical vein can be identified and ligated (just prior to opening the confluence) outside the pericardium at the level of the innominate vein. A transverse incision is made in the pulmonary venous confluence, and a parallel incision is placed in the dome of the left atrium beginning at the base of the left atrial appendage. The common pulmonary vein is then anastomosed to the left atrium, taking care to construct an unrestrictive connection. A right atriotomy is made to close the ASD.

2. Cardiac TAPVC The repair of cardiac TAPVC can be performed with bicaval cannulation and moderate hypothermia with the use of a vent or a cardiotomy sucker to capture the pulmonary venous return. A right atriotomy is performed with identification of the ASD and the orifice of the coronary sinus. The roof of the coronary sinus is excised into the left atrium. A patch of pericardium or prosthetic material is then placed to close the enlarged ASD, effectively channeling the pulmonary venous and coronary sinus return into the left atrium. The conduction system travels in proximity to the coronary sinus, and care must be taken while suturing the patch in this area to avoid heart block.

3. Infracardiac TAPVC For infracardiac connections, a brief period of hypothermic circulatory arrest is often required. The heart is rotated superiorly. The descending vertical vein is identified by opening the posterior pericardium. The connection to the descending vertical vein is ligated at the level of the diaphragm. An incision is made along the length of the pulmonary venous confluence with a parallel incision on the posterior wall of the left atrium. The pulmonary venous confluence is then anastomosed to the left atrium, taking care not to narrow the connection. Tissue from the descending vertical vein can be used in the anastomosis. A right atriotomy is performed through which the ASD is closed.

4. Recurrent pulmonary venous obstruction The app­roach to recurrent pulmonary venous obstruction is dependent on the level of obstruction. Obstruction can develop at the anastomosis or within the individual pulmonary veins. The latter may initially present as an anastomotic constriction, as the true extent of obstruction is not always apparent at first. Isolated narrowing of the anastomosis between the common pulmonary vein and left atrium often can be repaired with revision or patch augmentation of the anastomosis.

Obstruction of the individual pulmonary venous ostia is the greater challenge. Although the obstruction may initially appear to be limited to the ostium, progressive narrowing along the entire length of the vein into the hilum of the lung may occur with time. Repair of this lesion is technically challenging, and recurrent early obstruction is common. A new approach to recurrent pulmonary vein stenosis employs a “sutureless” technique utilizing in situ pericardium to create a neoatrium. The theory behind this repair is based on the concept that pulmonary venous obstruction results from inflammation induced locally by suture placement. Repair involves wide unroofing of the narrowed portion of each involved pulmonary vein from the left atrial anastomosis to the hilum. A wide flap of pericardium is then elevated with care taken to avoid disruption of posterior adhesions and injury to the phrenic nerve. This flap of pericardium is rotated over the unroofed pulmonary veins and sutured to the left atrial wall away from the venous ostia. A large neoatrium is then created into which pulmonary venous return can drain.

D. Prognosis

Early mortality in patients undergoing repair of TAPVC is associated with the initial degree of obstruction present. Early diagnosis and repair as well as optimal postoperative management, including aggressive treatment of pulmonary hypertension, have resulted in a dramatic reduction in operative risk. For patients surviving the perioperative period, the long-term survival and functional status are excellent.

Recurrent venous obstruction develops in 5%-17.5% of patients. Results following balloon angioplasty and/or stent insertion have been disappointing, and recurrent stenoses are the rule. Individual patch angioplasty of the ostia has also been utilized with poor long-term results. Lung transplantation has been considered in severe cases of extensive, bilateral disease. The mortality associated with reoperation for obstruction can be up to 59% when bilateral stenoses are present. The use of the sutureless technique for recurrent pulmonary vein obstruction has demonstrated improved survival and decreased recurrence.

Tricuspid Atresia

A. General Considerations

Tricuspid atresia refers to single-ventricle hearts that lack a communication between the right atrium and right ventricle. The only outlet for the right atrium is the ASD. If present, aneurysmal tissue of the septum primum may prolapse into the left atrium. The left atrium is normal in morphology but is often dilated. A normal communication with a mitral valve between the left atrium and left ventricle is present. The right ventricle is diminutive in size without an inlet portion. It is connected to the left ventricle by a VSD surrounded completely by muscle. The anatomic subtypes of tricuspid atresia are based on the relationship of the great arteries. Type I defects (70%) have normally related great vessels, type II (30%) have transposed great arteries, and type III (rare) have congenitally corrected TGAs. These types are further subclassified by the degree of obstruction to pulmonary blood flow, which is present in 45%-75% of patients. Aortic valve (10%) and aortic arch (25%) obstruction may also be present. Patients with tricuspid atresia are at increased risk for Wolff–Parkinson–White syndrome due to congenital and surgically acquired pathways.

B. Clinical Findings

The clinical presentation depends on the relationship of the great vessels and degree of restriction at the level of the atrial and ventricular septum. Most infants present with some degree of cyanosis. Systemic output is usually unobstructed. Prostaglandins may be necessary to maintain ductal patency in infants with severe obstruction to pulmonary blood flow.

C. Treatment

The initial palliation for most patients is the placement of a modified Blalock-Taussig shunt to maintain adequate pulmonary blood flow. A more complex initial palliation with a Norwood procedure may be necessary in the case of transposed great vessels. The remainder of the palliation involves a hemi-Fontan and Fontan procedure (discussed in the section on Hypoplastic Left Heart Syndrome).

D. Prognosis

The overall survival for tricuspid atresia is similar to that reported for other single-ventricle lesions palliated with a Fontan procedure. The survival is 83% at 1 year, 70% at 10 years, and 60% at 20 years.

Hypoplastic Left Heart Syndrome

A. General Considerations

A variety of congenital cardiovascular malformations may result in a functional single-ventricle anatomy, most commonly tricuspid atresia, pulmonary atresia, unbalanced AVSD, and HLHS. The most common lesion is HLHS. Approximately 1000 infants with HLHS are born in the United States each year. It is the most common severe congenital heart defect, comprising 7%-9% of all anomalies diagnosed within the first year of life. All single-ventricle lesions share the common physiology of only a single ventricle capable of supporting cardiac output. HLHS refers to a constellation of congenital cardiac anomalies characterized by marked hypoplasia or absence of the left ventricle and severe hypoplasia of the ascending aorta. The systemic circulation is dependent on the right ventricle via a PDA, and there is obligatory mixing of pulmonary and systemic venous blood in the right atrium. There is associated aortic valve stenosis or atresia and mitral valve stenosis or atresia. The descending aorta is essentially a continuation of the ductus arteriosus, and the ascending aorta and aortic arch represents a diminutive branch of this vessel. Initial management includes a prostaglandin infusion to maintain ductal patency and correction of metabolic acidosis. The patient may require intubation and ventilator adjustment to reduce supplemental oxygen and maintain a Pco₂ of about 40 mm Hg to avoid excessive pulmonary flow.

B. Treatment

Surgical approaches to the treatment of this problem include cardiac transplantation and staged reconstruction. In the context of improving results for staged reconstruction, risks of immunosuppression, and limited donor availability, competing risk analysis favors staged repair, and most centers pursue this option as primary therapy for HLHS. Transplantation is generally reserved for very high-risk patients, such as those with depressed RV function, severe tricuspid regurgitation, or significant coronary sinusoids.

The first successful palliation of HLHS was reported by Norwood on a series of infants operated between 1979 and 1981. This procedure has been technically refined over the years, but three essential components remain: atrial septectomy, anastomosis of the proximal pulmonary artery to the aorta with homograft augmentation of the aortic arch, and aortopulmonary shunt. A “hybrid Norwood” procedure is an alternate form of stage I palliation. This procedure involves bilateral pulmonary artery bands and PDA stenting with or without concommittant balloon atrial septostomy. The ultimate goal of surgical palliation in patients with a univentricular heart is the total diversion of all vena caval blood directly into the pulmonary arteries. The Fontan procedure was first successfully performed in a patient with tricuspid atresia but has since evolved as an excellent way to establish physiologic repair for patients with more complex forms of univentricular heart. The superior vena caval blood returns directly via an end-to-side anastomosis with the pulmonary artery (bidirectional Glenn) or through a right atrial-pulmonary artery connection (hemi-Fontan) performed at 4-6 months of age. The inferior vena caval flow is directed to the pulmonary artery with an intra-atrial baffle (lateral tunnel technique) or an extracardiac conduit at 2-4 years of age. All oxygenated pulmonary venous flow empties into the ventricular chamber through the AV valves to be ejected to the systemic circulation, while superior and inferior vena caval blood flows directly to the lungs to acquire oxygen prior to returning to the heart. For the Fontan procedure to be performed with a low operative mortality and an acceptable functional result, certain criteria must be met. Normal pulmonary artery pressure (< 20 mm Hg) and PVR (< 2 Woods units·m²) are the most important prerequisites. Additionally, it is essential that ventricular function and AV valve function be normal. Although the Fontan procedure cannot be considered a truly corrective operation, it offers benefits that cannot be equaled by those of any of the other palliative procedures. The major advantages include restoration of normal systemic oxygen saturation and reduction of ventricular volume overload.

C. Prognosis

Universally fatal only three decades ago, tremendous strides have been made in improving the outcomes for patients with HLHS. Of the three stages, the highest-risk stage of the repair remains the Norwood operation. During the 1990s, the hospital survival for the Norwood procedure across the United States was approximately 40%. A recent Society of Thoracic Surgeons Congenital Heart Surgery Database study reported 81% hospital survival rate for more than 2000 Norwood operations performed in 2009. Currently, interstage (time between the Norwood and hemi-Fontan operation) mortality is about 12%. Reported survivals for the hemi-Fontan and Fontan procedures have also been excellent at 98% for both operations. Overall, 75% of patients diagnosed with HLHS will survive through the Fontan procedure.

The current results for the Fontan procedure are excellent with hospital mortality ranging from 2% to 9%. The condition of survivors is generally good, and most attain a functional status of New York Heart Association class I or II. The long-term results have been reported with a 93% 5-year survival and a 91% 10-year survival. Although long-term results are encouraging, late complications may be seen. Continued surveillance for arrhythmias, congenital heart failure, protein-losing enteropathy, and hepatic dysfunction remains important.

1. Left-to-Right Shunting

Atrial Septal Defect

A. General Considerations

Cardiac septation occurs between the third and sixth weeks of fetal development. The septum primum, which arises from the roof of the common atrium and descends inferiorly, initially divides the common atrium. The ostium primum is the opening below the inferior edge of the septum primum, which is obliterated as the septum primum fuses with the endocardial cushions. The ostium secundum forms in the midportion of the septum primum prior to closure of the ostium primum. The septum secundum also arises from the roof of the atrium and descends along the right side of the septum primum and covers the ostium secundum. This creates a flap valve whereby blood from the inferior vena cava may preferentially stream beneath the edge of the septum secundum and through the ostium secundum into the left atrium. After birth, the increase in left atrial pressure usually closes this pathway.

An ASD is a hole in the atrial septum (Figure 19–31). ASDs are the third-most common congenital heart defect, occurring in 1 out of 1000 live births and representing 10% of congenital heart defects. The most common ASD is the secundum defect, which occurs when the ostium secundum is too large for complete coverage by the septum secundum. Ostium secundum defects account for about 80% of ASDs. An ostium primum ASD, representing 10% of ASDs, occurs as a result of failure of fusion of the septum primum with the endocardial cushions (ostium primum defect is discussed later in the section on Atrioventricular Septal Defects [AVSD]). A third type of ASD is the sinus venosus defect, seen in about 10% of cases. Sinus venosus ASDs are caused by abnormal fusion of the venous pathways with the atrium and are characterized by defects high in the atrial septum near the orifice of the superior vena cava or, less commonly, low in the atrial septum near the inferior vena cava. Sinus venosus defects are frequently associated with partial anomalous pulmonary venous connection, usually with the right upper pulmonary vein draining into the superior vena cava near the cavoatrial junction. The rarest type of ASD is the unroofed coronary sinus septal defect. This occurs when there is loss of the common wall between the coronary sinus and the left atrium adjacent to the atrial septum. This unroofing of the coronary sinus leads to a communication between the right and left atria at the site of the coronary sinus.

Failure of postnatal fusion of the septum secundum to the septum primum results in a persistent slit-like communication known as a PFO. PFOs are extremely common in the general population, and autopsy studies have demonstrated a prevalence of 27%. PFOs are generally considered separate from other ASDs because of the absence of significant shunting, but they remain important clinically because of the occurrence of paradoxical embolization. A paradoxical embolus is usually a blood clot arising from a systemic vein, which would normally pass to the lungs, but in the presence of a septal defect may instead cross into the systemic circulation.

B. Clinical Findings

ASDs lead to increased pulmonary blood flow secondary to left-to-right shunting. Shunting at the atrial level is determined by the size of the defect and by the relative ventricular compliance (ie, blood preferentially fills the more compliant ventricle). At birth, both chambers are equally compliant, but as PVR falls, the right ventricle remodels and becomes more compliant. Shunting across the atrial septum causes a volume load on the right heart. A volume load is created by additional venous return to a chamber during diastole.

The volume overload from an ASD is usually well tolerated, and patients are frequently asymptomatic. Symptoms tend to develop when the ratio of pulmonary to systemic blood flow (Q_p/Q_s) exceeds two. The most common symptoms are fatigue, shortness of breath, exercise intolerance, and recurrent respiratory infections. Older patients with untreated ASDs tend to develop atrial dysrhythmias, and adults may develop congestive heart failure and RV dysfunction. Pulmonary vascular obstructive disease may develop rarely as a late complication of untreated ASD. Paradoxical embolization is also an important potential complication of ASD.

The classic physical findings in patients with ASDs include fixed splitting of the second heart sound and a systolic ejection murmur at the left upper sternal border due to increased flow across a normal pulmonary valve. A diastolic flow murmur across the tricuspid valve is occasionally audible. A prominent RV lift and increased intensity of the pulmonary component of the second heart sound may occur with pulmonary hypertension. Chest radiography shows cardiomegaly, with enlargement of the right atrium, right ventricle, and pulmonary artery. EKG frequently demonstrates right axis deviation and an incomplete right bundle branch block. When right bundle branch block occurs with a leftward or superior axis, the diagnosis of AVSD should be considered. Echocardiography confirms the diagnosis of ASD and defines the anatomy. Cardiac catheterization is important in selected cases to assess PVR in older patients, but it is used more frequently with therapeutic intent for device closure of ASDs.

C. Treatment

Because of the long-term complications associated with ASD, repair is recommended for all patients with symptomatic defects and in asymptomatic patients in whom the Q_p/Q_s is greater than 1.5. Repair is usually performed in children prior to school age. Closure of ASDs may be performed surgically or using a device deployed in the cardiac catheterization lab.

Surgical repair is usually recommended for large secundum defects and for most other types of ASDs. The heart is usually exposed by median sternotomy. Other surgical approaches have been proposed, including minimally invasive techniques, but there are technical drawbacks associated with each of the alternative approaches. In most cases, a limited midline incision with a partial lower sternal split provides adequate exposure and a cosmetically acceptable scar. The atrial septum is exposed through a right atriotomy. Small secundum defects or PFOs may sometimes be closed primarily by suturing the edge of the septum primum to the edge of the septum secundum. More commonly, larger defects are closed using a patch (polytetrafluoroethylene or autologous pericardium) and a running polypropylene suture. When anomalous pulmonary venous drainage is present, a baffle is created to redirect the flow across the ASD. In all cases, care is taken to deair the left atrium to avoid the complication of air embolization.

The first transcatheter device closure of an ASD was performed in 1976. A number of devices are currently available for percutaneous closure of a secundum ASD, and success rates for device deployment are greater than 90%. Device closure has the advantages of fewer complications and a shorter hospitalization. Device closure of small to moderate secundum ASDs and PFOs has now become the standard of care at most large centers.

Occasionally, adults will present with a newly diagnosed ASD. Many studies have confirmed that ASD closure in adults over the age of 40 increases survival and limits the development of heart failure. When the Q_p/Q_s is less than 1.5 and the ratio of pulmonary to systemic vascular resistance (R_p/R_s) is greater than 0.7, significant pulmonary vascular obstructive disease is usually present. A PVR in excess of 10-12 Woods units·m² represents a contraindication to ASD closure.

D. Prognosis

Operative mortality for ASD repair is close to 0%. Atrial arrhythmias (1.2%) and postpericardiotomy syndrome (4.7%) are the most common postoperative complications. The long-term survival for patients undergoing ASD repair in childhood is normal. The major long-term complication following surgical closure of ASD is the development of supraventricular arrhythmias, although the risk is lowered when the ASD is closed in childhood. The persistence of this risk despite relief of right-sided volume overload is thought to be related to incomplete atrial remodeling or due to the presence of the atriotomy scar. Longer follow-up is required to determine whether device closure alters the risk of atrial dysrhythmias.

Ventricular Septal Defect

A. General Considerations

Ventricular septation is a complex process that requires accurate development and alignment of a number of structures including the muscular interventricular septum, the AV septum (arising from the endocardial cushions), and the infundibular septum (which divides the outflow tracts of the right and left ventricles). The membranous septum is a fibrous portion of the ventricular septum, which is adjacent to the central fibrous body (where the mitral, tricuspid, and aortic valve annuli make contact).

VSDs are the most common congenital heart anomalies (with the exception of bicuspid aortic valve, which occurs in about 1.3% of the population). VSDs are present in about 4 of 1000 live births and represent about 40% of congenital heart defects. VSDs are classified based on their location in the ventricular septum (Figure 19–32). The most common defects are perimembranous (80%), which are located in the area of the membranous septum. Inlet defects (5%) are located beneath the septal leaflet of the tricuspid valve and are sometimes called atrioventricular (AV) canal-type defects. Defects located high in the ventricular septum are outlet defects (10%). Outlet VSDs are typically adjacent to both the pulmonary and aortic valves. Outlet defects are also known by several other names, including supracristal, infundibular, or doubly committed subarterial. Outlet defects are more common in the Asian population. Muscular (or trabecular) VSDs (5%) are completely bordered by muscle. Muscular VSDs are frequently multiple and may be associated with perimembranous or outlet defects. The size of VSDs varies. By definition, a VSD is nonrestrictive when its size (or the cumulative size of multiple defects) is greater than or equal to the size of the aortic annulus.

B. Clinical Findings

A VSD causes increased pulmonary blood flow due to left-to-right shunting primarily during systole. This creates a volume load on the left heart (the left atrium and ventricle receive the increased venous return during diastole). The right ventricle is not volume loaded (blood is ejected from the left ventricle through the VSD and directly into the pulmonary circulation), but it does experience a pressure load. The volume of shunt flow is determined by the size of the defect and by the ratio of R_p/R_s. After birth, the PVR is still high, and shunting across a VSD is sometimes minimal. Over the first several weeks of life, shunting tends to increase as the PVR normally falls. Therefore, a patient with a large VSD may be asymptomatic at birth but eventually develop severe congestive heart failure.

The natural history for patients with isolated VSDs is highly variable. Most VSDs are restrictive and tend to close spontaneously during the first year of life. Large VSDs are nonrestrictive, resulting in RV and pulmonary pressures that are systemic or nearly systemic, and high pulmonary blood flow with Q_p/Q_s ratios greater than 2.5-3. Moderate VSDs are restrictive, with pulmonary pressures that are one-half systemic (or less) and Q_p/Q_s ratios of 1.5-2.5. Small VSDs are highly restrictive; RV pressures remain normal, and the Q_p/Q_s is less than 1.5. Patients with large VSDs tend to develop symptoms of congestive heart failure by 2 months of age. Untreated, excessive pulmonary blood flow leads to pulmonary vascular obstructive disease by the second year of life. Patients with smaller VSDs may remain asymptomatic. In patients with outlet VSDs, prolapse of the aortic valve may occur, producing aortic insufficiency.

Signs of heart failure in infants with large VSDs include tachypnea, hepatomegaly, poor feeding, and failure to thrive. On physical examination, there is a pansystolic murmur at the left sternal border. Usually, the murmur is louder with smaller defects. The precordium is active. The pulmonary component of the second heart sound is accentuated in the presence of pulmonary hypertension. Chest radiography shows increased pulmonary vascular markings and cardiomegaly. EKG is significant for RV hypertrophy.

Patients with small VSDs have little shunting and are usually asymptomatic, having only a pansystolic murmur. Patients with moderate VSDs manifest symptoms and signs proportional to the degree of shunting.

In patients who have developed significant pulmonary vascular obstructive disease, the volume of left-to-right shunting is decreased, and the murmur may disappear. Eisenmenger physiology results when the shunt flow reverses to right-to-left, creating cyanosis.

The diagnosis of VSD is confirmed by echocardiography, which accurately defines the anatomy and excludes the presence of associated defects. Cardiac catheterization is used selectively in older children and adults in whom elevated PVR is suspected. Pulmonary vascular resistance is calculated by the following formula:

where PA_mean is the mean pulmonary artery pressure and LA is the left atrial pressure. The units of resistance by this formulation (using pressures in millimeters of mercury and pulmonary flow in liters per minute) are Woods units (which can be expressed in dynes·sec/cm⁵ by multiplying by 80). PVR may be fixed or reactive, and at the time of cardiac catheterization, response to various pulmonary vasodilators may be assessed.

C. Treatment

The management of a patient with a VSD depends on the size of the defect, the type of the defect, the shunt volume, and the PVR. In general, patients with large defects who have intractable congestive heart failure or failure to thrive should undergo early surgical repair. If the congestive symptoms can be moderated by medical therapy, then surgery may be deferred until 6 months of age. Patients with moderate VSDs may be safely followed. If closure has not occurred by school age, then surgical closure is indicated. Small VSDs with Q_p/Q_s of less than 1.5 do not require closure. There is a small long-term risk of endocarditis for these patients, but this can be minimized with the appropriate use of prophylactic antibiotics. Patients with outlet VSDs have a significant risk of developing aortic insufficiency due to leaflet prolapse, and, therefore, all of these patients should undergo surgical closure. Older children and adults must undergo catheterization to assess the pulmonary circulation. When there is a fixed PVR greater than 8-10 Woods units·m², then surgery is contraindicated.

Exposure of the ventricular septum is most often achieved by making a right atriotomy and retracting the leaflets of the tricuspid valve. This provides access to perimembranous, inlet, and most trabecular VSDs. Outlet VSDs are frequently best exposed via a pulmonary arteriotomy because the defect lies just beneath the valve. Muscular VSDs located near the ventricular apex can be very difficult to expose, and an apical ventriculotomy may be necessary. Once the defect is exposed, it is closed using a polytetrafluoroethylene patch and a running polypropylene suture, although some centers may prefer other patch material or interrupted suture technique. It is important to understand the anatomy of the conduction tissue when closing VSDs. The AV node is an atrial structure that lies at the apex of an anatomic triangle (known as the triangle of Koch) formed by the coronary sinus, the tendon of Todaro (a prominent band leading from the inferior vena cava and inserting in the atrial septum), and the septal attachment of the tricuspid valve. The node then gives rise to the bundle of His, which penetrates the AV junction beneath the membranous septum. The bundle of His then bifurcates into right and left bundle branches, which pass along either side of the muscular ventricular septum. In the presence of a perimembranous VSD, the bundle of His passes along the posterior and inferior rim of the defect, generally on the left ventricular side. In this critical area, sutures must be placed superficially on the RV side a few millimeters from the edge of the defect. The bundle of His tends to run along the posterior and inferior margin of inlet VSDs as well. The conduction tissue is usually remote from outlet and trabecular VSDs.

Pulmonary artery banding is a palliative maneuver used to protect the pulmonary circulation from excessive blood flow. Pulmonary artery banding is currently performed only in patients who are felt to be poor candidates for VSD closure because of either associated illness or anatomic complexity, such as multiple muscular VSDs (“Swiss cheese” septum). A band is placed around the main pulmonary artery and tightened to achieve a distal pulmonary artery pressure of about one-half systemic. The band is secured to the adventitia of the pulmonary artery to prevent its migration. Distal migration may result in narrowing and poor growth of one or both branch pulmonary arteries, while proximal migration can cause deformity of the pulmonary valve. Later, when the patient is a candidate for VSD closure, the band must be removed. Repair of the main pulmonary artery at the band site is usually necessary and can typically be accomplished by scar resection and primary closure or patch repair.

Transcatheter devices allow closure of some VSDs in the cardiac catheterization lab. For specific VSDs, such as muscular, device closure may be preferable. Complications with device closure include complete heart block (3.8%), device embolization (0.01%), and aortic insufficiency (0.03%). For simple perimembranous VSDs, the risk of device closure is in excess of traditional surgical closure.

D. Prognosis

Surgical closure of a VSD is associated with a mortality of less than 1%. Potential complications include injury to the conduction tissue and injury to the tricuspid or aortic valves. Transient heart block may result from tissue swelling or injury from retraction, but permanent heart block occurs in less than 2% of cases. When heart block develops after surgery, patients are usually observed for a period of 7-10 days prior to permanent pacemaker implantation. Tricuspid insufficiency may be precipitated by annular distortion or chordal restriction by the VSD patch or sutures. The aortic valve may also be injured by inaccurate suturing (especially in perimembranous and outlet defects). A residual VSD is seen in about 5% of cases, and reoperation is indicated when significant shunting persists (Q_p/Q_s > 1.5) or the residual defect is larger than 2 mm in size. The Q_p/Q_s ratio can be calculated by measuring oxygen saturations and using the following formula derived from the Fick equation:

where Ao is the aortic (or systemic) saturation, SVC is the saturation in the superior vena cava, PV is the saturation in the pulmonary veins (which is usually estimated to be 95%-100%), and PA is the saturation in the pulmonary arteries. Intraoperative echocardiography is used routinely to identify residual defects, which can then be repaired before the patient leaves the operating room.

Atrioventricular Septal Defect

A. General Considerations

AVSDs represent a group of congenital abnormalities bound by a variable deficiency of the atrioventricular septum immediately above and below the AV valves. Other terms commonly applied to an AVSD include AV canal defects, endocardial cushion defects, and atrioventricular communis. Complete AVSDs have a single common AV valve orifice resulting in a single five-leaflet valve overlying both the right and left ventricles. Incomplete AVSDs have two separate AV valve orifices (tricuspid and mitral) with the mitral valve invariably having a cleft in the anterior leaflet. While most incomplete AVSDs have no ventricular level shunting, the classification of AVSDs as complete and incomplete depends only on the valve anatomy, not on the presence or absence of a VSD. Incomplete defects without associated ventricular level shunting have also been termed ostium primum ASDs, while those with a VSD have been described as intermediate or transitional AVSDs. AVSDs represent approximately 4% of congenital cardiac anomalies and are frequently associated with other cardiac malformations. AVSDs comprise 30%-40% of the cardiac abnormalities seen in patients with Down syndrome.

A complete AVSD is characterized by a common atrioventricular orifice, rather than separate mitral and tricuspid orifices, and a deficiency of endocardial cushion tissue, which results in an ASD and an inlet type of VSD (Figure 19–33). AVSDs were subclassified by Rastelli into the following three types according to the morphology of the anterior leaflet of the common AV valve:

• Type A: The anterior bridging leaflet is divided and attached to the septum by multiple chordae.

• Type B: The anterior bridging leaflet is attached to a papillary muscle in the right ventricle.

• Type C: The anterior bridging leaflet is free-floating with no attachments except to the valve annulus.

When both left and right AV valves equally share the common AV valve orifice, the AVSD is termed balanced. Occasionally, the orifice may favor the right AV valve (right dominance) or the left AV valve (left dominance). In marked right dominance, the left AV valve and left ventricle are hypoplastic and frequently coexist with other left-sided abnormalities, including aortic stenosis, hypoplasia of the aorta, and coarctation. Conversely, marked left dominance results in a deficient right AV valve with associated hypoplasia of the right ventricle, pulmonary stenosis or atresia, and TOF. Patients with severe imbalance require staged single-ventricle reconstruction.

The conduction tissue is displaced in an ASVD and is at risk during the surgical repair. The AV node is located posteriorly and inferiorly of its normal position toward the coronary sinus in the triangle of Koch. This triangle is bounded by the coronary sinus, the posterior attachment of the inferior bridging leaflet, and the rim of the ASD. The bundle of His courses posteriorly and inferiorly to run along the leftward aspect of the crest of the VSD, giving off the left bundle branch and continuing as the right bundle branch.

Cardiac anomalies associated with AVSDs include: PDA (10%) and TOF (10%). Important abnormalities of the left AV valve include single papillary muscle (parachute mitral valve) (2%-6%) and double orifice mitral valve (8%-14%). A persistent left superior vena cava with or without an unroofed coronary sinus is encountered in 3% of patients with an AVSD. Double-outlet right ventricle (2%) significantly complicates or may even preclude complete surgical correction. As mentioned previously, left ventricular outflow tract obstruction from subaortic stenosis or redundant AV valve tissue occurs in 4%-7%.

B. Clinical Findings

The predominant hemodynamic features of an AVSD are the result of left-to-right shunting at the atrial and ventricular levels. In the absence of ventricular level shunting, the hemodynamics and clinical presentation of a patient with an incomplete AVSD resemble that of a typical secundum ASD with right atrial and RV volume overload. Patients with a complete AVSD with both atrial-level and ventricular-level shunting generally present early in infancy with signs and symptoms of congestive heart failure. In addition, moderate or severe left AV valve regurgitation occurs in approximately 10% of patients with an AVSD worsening the clinical picture. On physical examination, the precordium is hyperactive, often with a prominent thrill. Auscultatory findings include a systolic murmur along the left sternal border, a high-pitched murmur at the apex from the left AV valve regurgitation, and a middiastolic flow murmur across the common A-V valve. In the presence of elevated PVR, there may be a split first heart sound. Significant cardiomegaly and pulmonary overcirculation are found on the CXR. Electrocardiogram reveals biventricular hypertrophy, atrial enlargement, prolonged PR interval, leftward axis, and counterclockwise frontal plane loop. Echocardiography is diagnostic, defining the atrial and ventricular level shunting, valvular anatomy, and any associated anomalies. Up to 90% of untreated individuals with a complete AVSD develop pulmonary vascular disease by 1 year of age due to the large left-to-right shunt, potentially exacerbated by the associated AV valve regurgitation. Patients with trisomy 21 tend to develop pulmonary vascular obstructive disease earlier than chromosomally normal infants due to small airway disease, chronic hypoventilation, and elevated Pco₂. Initial aggressive medical management is undertaken to relieve the symptoms of congestive heart failure. Elective surgical correction should be performed by age 3-6 months. Earlier intervention is indicated for failure of medical management.

Cardiac catheterization should be performed for patients over the age of 1 year, for patients with signs or symptoms of increased PVR, or in some cases to further evaluate other associated major cardiac anomalies. If the PVR is high, it is important to remeasure it while the child is breathing 100% oxygen with and without nitric oxide. If the pulmonary resistance falls, it implies that much of the elevated resistance is dynamic and can be managed in the perioperative period by ventilatory manipulation, supplemental oxygen, and nitric oxide. More recently, sildenafil has been shown to decrease elevation in PVR in children with congenital heart disease. Markedly elevated PVR (> 10 Woods units·m²) that does not respond to oxygen administration is generally considered a contraindication to repair.

C. Treatment

Operative treatment is almost always necessary as soon as symptoms are observed to prevent further clinical deterioration. Even in the absence of symptoms, operation is best performed before 6 months of age. Pulmonary artery banding, which permits delaying the repair until the child is larger, is no longer used today except in select complex or single-ventricle cases, extremely low birth weight or prematurity, and very poor clinical condition. This approach exposes the child to the risks of two operations, and the overall mortality exceeds that of primary repair in infancy. Patients with incomplete AVSDs usually require repair within the first few years of life.

Two techniques are widely employed for the repair of complete AVSDs: a 1-patch technique and a 2-patch technique. Incomplete AVSDs are repaired with the single-patch technique. Regardless of which approach is selected, the goals are to close the ASD and VSD and to separate the common AV valve into two nonstenotic, competent valves. The cleft in the anterior leaflet of the mitral valve is generally closed to lessen the risk of long-term mitral regurgitation. For the 2-patch technique, separate patches are used for the ASD and VSD. For the 1-patch technique, the superior and inferior bridging leaflets are divided along a line separating them into right and left components. A single patch is utilized to close both the ventricular and ASDs. The cut edges of the leaflets are then resuspended to the patch. For defects with a small VSD component, a modified single-patch technique may be employed. For this method, a single patch is sewn directly to the rim of the VSD, sandwiching the bridging leaflets between the patch and the crest of the VSD.

The short-term and long-term success of the operation is highly dependent on the status of the PVR and the surgeon’s ability to maintain competence of the mitral valve. In developed countries, it is fortunately relatively uncommon for patients to present late in with an AVSD and refractory PVR elevations. Although earlier reports recommend that the cleft in the left AV valve should not be closed and the valve should be treated as a trileaflet structure, most authors now believe that closure of the cleft is an important mechanism in preventing postoperative left AV valve regurgitation. Significant AV valve regurgitation at the conclusion of surgery, severe dysplasia of the left AV valve, and failure to close the cleft of the left AV valve have been identified as important risk factors for reoperation. Significant postoperative left AV valve regurgitation is also a risk factor for operative and long-term mortality. The cleft should not be completely closed in the presence of a single papillary muscle to avoid causing the left AV valve stenosis. In the case of a double-orifice valve, the bridging tissue should not be divided to create a single opening in the valve.

D. Prognosis

Operative mortality is related largely to associated cardiac anomalies and left AV valve regurgitation. Mortality for repair of uncomplicated incomplete AVSDs is 0%-1.6%, while the addition of left AV valve regurgitation increases mortality to 4%-6%. For complete AVSDs, the mortality without left AV valve regurgitation is approximately 4%-5%, compared with 13% when significant degrees of regurgitation are present. The difference in operative mortality between patients with and without regurgitation underscores the importance of careful management of the left AV valve.

The majority of reoperations after repair of AVSD are due to left AV valve regurgitation or the development of subaortic stenosis. Significant postoperative AV valve regurgitation occurs in 6%-26% of patients, necessitating reoperation for valve repair or replacement in 3%-12%. The incidence of permanent complete heart block is approximately 1%-2%. Heart block encountered in the immediate postoperative period may be transient due to edema of or trauma to the AV node or bundle of His. However, right bundle branch block is common (22%).

Patent Ductus Arteriosus

A. General Considerations

The ductus arteriosus is a normal fetal vascular structure that allows blood from the right ventricle to bypass the high-resistance pulmonary vascular bed and pass directly to the systemic circulation. The ductus communicates between the main pulmonary artery (or proximal left pulmonary artery) and the proximal descending thoracic aorta. Histologically, the media of the ductus contains a predominance of smooth muscle cells, while the media of the aorta and pulmonary artery contain well-developed elastic fibers. Vasocontrol of the ductus is mediated by two important mechanisms: oxygen tension and prostaglandin levels. During fetal development, low oxygen tension and high levels of circulating prostaglandin maintain ductal patency. During the final trimester, the ductus becomes less sensitive to prostaglandins and more sensitive to the effects of oxygen tension. Following birth, the rise in oxygen tension and fall in prostaglandins (which were previously supplied principally by the placenta) lead to ductal closure, which is usually complete by 12-24 hours. After closure, the ductus becomes a fibrous cord known as the ligamentum arteriosum. Failure of closure of the ductus leads to the condition called patent ductus arteriosus (PDA) which occurs in about 1 out of 1200 live births and accounts for 7% of congenital heart defect. The incidence is much higher in premature infants (> 20%). This elevated incidence is thought to be related to immaturity of the ductal wall resulting in impaired sensitivity to oxygen tension.

PDA may occur as an isolated defect, or it may occur in association with a number of other anomalies. Patency of the ductus arteriosus is desirable in a number of defects in which there is either inadequate pulmonary blood flow (such as pulmonary atresia) or inadequate systemic blood flow (as in severe coarctation of the aorta). The discovery that extrinsic delivery of prostaglandins can maintain ductal patency has played a critical role in improving the survival of these patients.

B. Clinical Findings

The physiologic manifestation of PDA is shunting of blood across the ductus. The shunt volume is determined by the size of the ductus and by the ratio of pulmonary to systemic vascular resistance. At birth, the PVR drops dramatically and continues to decline over the first several weeks of life. As a result, shunting across a PDA is from left-to-right. Excessive pulmonary blood flow can lead to congestive heart failure. In extreme cases, hypotension and systemic malperfusion may result. Patients with a large PDA who survive infancy tend to develop pulmonary vascular obstructive disease. Eisenmenger physiology results when the PVR exceeds the systemic vascular resistance, producing a reversal of shunting across the ductus to right-to-left. This leads to cyanosis and, eventually, RV failure. Small PDAs may persist to adulthood without producing any symptoms or physiologic derangement. Endocarditis and endarteritis have been reported as long-term complications of PDA.

In patients with PDA, symptoms are proportional to the shunt volume and the presence of associated defects. Left-to-right shunting produces volume overload of the left heart. Infants with congestive heart failure demonstrate symptoms of tachypnea, tachycardia, and poor feeding. Older children may present with recurrent respiratory infections, fatigue, and failure to thrive. Physical findings include a widened pulse pressure and a continuous “machinery” murmur heard best along the left upper sternal border. Chest radiography shows increased pulmonary vascular markings and left heart enlargement. Left ventricular hypertrophy and left atrial enlargement may be evident on the electrocardiogram. Echocardiography is the diagnostic method of choice. Diagnostic cardiac catheterization is performed only in older patients with suspected pulmonary hypertension to evaluate for pulmonary vascular obstructive disease. More frequently, catheterization is utilized for transcatheter occlusion of the ductus.

C. Treatment

PDA closure is performed for all symptomatic patients. Closure is also recommended for asymptomatic patients due to the risk of heart failure, pulmonary hypertension, and endocarditis. Closure of the ductus may be accomplished by one of three approaches: pharmacologic, surgical, and endovascular. Indomethacin, which is a prostaglandin inhibitor, stimulates PDA closure in premature infants. It is rarely effective in full-term infants. The dosing regimen is 0.1-0.2 mg/kg intravenously at 12- or 24-hour intervals for a total of three doses. This is effective in about 80% of premature babies. Due to its side effects, indomethacin is contraindicated in patients with sepsis, renal insufficiency, intracranial hemorrhage, or bleeding disorders. Failure of indomethacin after two complete courses results in referral for surgical closure.

The surgical approach to PDA is through a left posterolateral thoracotomy via the third or fourth intercostal space. The pleura is incised over the proximal descending thoracic aorta, which allows medial retraction of the vagus nerve. The recurrent laryngeal nerve curves behind the ductus and should be protected throughout the procedure. Dissection is then performed to demonstrate the pertinent anatomy. In many cases, the ductus is the largest vascular structure present, and it must not be confused with the aorta. Ductal tissue is extremely friable, so direct manipulation is minimized. In premature infants, the ductus is controlled with a single surgical clip; this procedure is commonly performed in the neonatal intensive care unit, thereby avoiding problems associated with patient transfer. In older patients, occlusion of the ductus is achieved with simple silk ligature or, preferably, by division between ligatures to minimize recurrence.

Recently, thoracoscopic techniques have been developed to perform PDA ligation. This approach has the potential benefits of decreased pain and quicker recovery. Disadvantages include a substantial learning curve and increased operating time.

A number of endovascular devices have been developed for the purpose of transcatheter occlusion of the PDA. This approach is very successful in older infants, children, and adults with small and moderate sized PDAs and has become the treatment of choice at many centers. Surgical therapy is reserved for PDAs having a large diameter or very short length.

Rarely, an adult will present with a significant PDA. These patients must be carefully evaluated for the presence of pulmonary vascular obstructive disease prior to ductal closure. If the patient is not a candidate for device closure, surgical closure can be problematic. Calcification of the ductal wall is common in adults, which makes ligation hazardous. In some cases, cardiopulmonary bypass may be required with patch closure of the ductus from within the pulmonary artery.

D. Prognosis

Closure of the ductus by surgical or transcatheter techniques is achieved with a mortality that approaches zero. Potential complications include pneumothorax, recurrent laryngeal nerve injury, and chylothorax (from injury to the thoracic duct). Long-term survival should be normal following PDA ligation in most patients. Survival in premature infants depends primarily on the extent of prematurity with its attendant complications.

2. Right-Sided Anomalies

Pulmonary Stenosis

A. General Considerations

Isolated pulmonary stenosis occurs in 5%-8% of all congenital cardiac anomalies. The pulmonary valve is usually trileaflet with fusion of the commissures. The valve can appear thickened and domed on echocardiography. Most patients have an associated PFO or a secundum ASD. Pulmonary stenosis may be valvar or subvalvar due to muscular narrowing of the infundibulum (Figure 19–34).

B. Clinical Findings

Young infants with severe pulmonary stenosis present with failure to thrive, right heart failure, and possibly hypoxic spells. Older children tend to have mild to moderate stenosis that is asymptomatic. They may, however, complain of shortness of breath with exertion or arrhythmias. The murmur of pulmonary stenosis tends to be prominent and therefore is not missed on routine examination. The presence of a systolic ejection murmur should prompt further workup, including an echocardiogram, which is diagnostic. Patients may be followed symptomatically with mild to moderate pulmonary stenosis. Surgical or catheter-based intervention should be considered for a gradient higher than 50 mm Hg, progressive ventricular hypertrophy, or new tricuspid regurgitation.

C. Treatment

Neonates presenting with profound cyanosis from severe pulmonary stenosis need to be placed on PGE₁ to maintain ductal patency. The ductus will maintain adequate pulmonary blood flow so that the patient can be stabilized. For isolated pulmonary stenosis, balloon valvuloplasty by an interventional cardiologist is highly successful and has replaced surgical intervention for the majority of patients. Asymptomatic infants with systemic RV pressures from pulmonary stenosis are also excellent candidates for balloon dilation. Surgical valvotomy or a transannular patch for pulmonary stenosis is reserved for patients who have failed balloon dilation, who have a severely hypoplastic valve annulus, or who have other associated anomalies including muscular infundibular narrowing. Older patients with progressive isolated pulmonary stenosis are excellent candidates for elective balloon dilation when they develop elevated RV pressures.

D. Prognosis

Early mortality for patients with critical pulmonary stenosis is 3%-10%. Restenosis occurs in 10%-25% of patients. Once the outflow obstruction is relieved, the RV hypertrophy and tricuspid insufficiency regress. Although overall survival is excellent for isolated pulmonary stenosis, over 50% of patients will require additional interventions, including repeat balloon dilation, pulmonary valve replacement, and ASD closure. Late atrial and ventricular arrhythmias occur in 38% of patients. Twenty-five year survival is 90%-96%.

Ebstein’s Anomaly

A. General Considerations

Ebstein’s malformation was first described by Wilhelm Ebstein in 1866 as a constellation of clinical findings resulting from an abnormality of the tricuspid valve. It has become evident over time that the malformation is a disease of the entire right ventricle and the development of the tricuspid valve. It involves a spectrum of anatomical abnormalities of variable severity, which include apical displacement of the septal and mural leaflets of the tricuspid valve, which have failed to delaminate from the underlying myocardium; thinning or atrialization of the inlet component of the right ventricle, with variable dilation; and malformation of the anterosuperior leaflet, with anomalous attachments, redundancy, and fenestrations. Several other cardiac anomalies are often associated with the RV changes, such as atrial and VSDs, obstruction of the RV outlet, and Wolff–Parkinson–White syndrome. Ebstein’s malformation can also afflict the left-sided systemic AV valve in the setting of congenitally corrected transposition.

B. Clinical Findings

The malformation is rare, accounting for no more than 1% of all congenital cardiac anomalies. Due to the significant anatomic variability in the abnormalities of the tricuspid valve and right ventricle, the age at presentation and severity of symptoms can also be highly variable. Patients who present in infancy have the poorest prognosis. There is a high rate of fetal death, hydrops, and pulmonary hypoplasia when the diagnosis is made during fetal life. Cyanosis is the most common presentation in infancy. These patients have severe tricuspid regurgitation with a poorly functioning right ventricle in the face of elevated pulmonary arterial resistance. The result is a state of low cardiac output dependent on right-to-left shunting across the fossa ovalis.

With less severe derangements of the tricuspid valve and preserved ventricular function, patients tend to present later in adolescence or early adulthood. Many patients are asymptomatic and present with a murmur noted on physical examination. In symptomatic patients, a common presentation involves the new onset of atrial arrhythmias or reentrant tachycardia. Exercise tolerance may be diminished, with cyanosis during extreme exertion if an ASD is present. Those patients with an intact atrial septum will often progress to congestive heart failure with increasing cardiomegaly.

Echocardiography is usually sufficient for accurate diagnosis and anatomic evaluation. The degree of displacement, tethering, and dysplasia of the valvar leaflets, as well as the amount of regurgitation, can be determined. Ventricular function and the extent of atrialization of the right ventricle can also be evaluated. Additional abnormalities, including the presence and direction of a shunt at the atrial level, can be assessed. Electrocardiographic findings include incomplete right bundle branch block, right axis deviation, ventricular preexcitation, and atrial arrhythmias. The CXR can vary from normal, in patients with mild anatomic abnormalities, to the classic “wall-to-wall” heart. Cardiac catheterization is rarely necessary.

C. Treatment

As noted previously, neonates often present with profound cyanosis and may require prostaglandins to maintain adequate flow of blood to the lungs during the early neonatal period when pulmonary resistance is high. It is important to distinguish functional from anatomic pulmonary atresia. In patients with functional atresia, it may be possible to wean them from the infusion of prostaglandins while maintaining adequate saturations of oxygen as pulmonary resistance falls. These patients can then be followed for development of further symptoms.

In neonates who cannot be weaned from prostaglandins due to unacceptable levels of hypoxemia, or in those with anatomic pulmonary atresia, it is necessary to construct a systemic-to-pulmonary shunt to maintain adequate pulmonary blood flow. For neonates who also develop significant symptoms of congestive heart failure while on prostaglandin, it is necessary to address the underlying valvar pathology. The options include closure of the tricuspid valve, with or without fenestration, along with construction of a modified Blalock-Taussig shunt, repair of the tricuspid valve if ventricular function is reasonable, or cardiac transplantation.

In the older patient with progressive symptoms, a variety of surgical options exist to address the malformed tricuspid valve. Most are based on techniques designed to mobilize the leading edge of the anterosuperior leaflet, aiming to create a competent monocusp valve with or without plication of the atrialized portion of the right ventricle. There is ongoing debate as to the necessity of obliterating the atrialized portion of the right ventricle. Historically, plication of this portion of the ventricle has been an integral part of most repairs, albeit that no clear physiologic benefit with regards to improved ventricular function has been demonstrated. In addition, the potential exists for injury to the right coronary artery as a result of the plication, which may adversely impact late outcomes and contribute to ventricular arrhythmias.

Replacement of the tricuspid valve is a final option. The late survival free from reoperation, however, has been equivalent to valvar repair. If replacement is required, heterografts are preferred over mechanical valves due to risks of thrombosis. Other options using tissue valves include the insertion of pulmonary autografts, mitral valve homografts, and “top hat” mounted pulmonary or aortic homografts. When replacing the valve, the sutures should be brought around the coronary sinus, leaving it to drain into the right ventricle so as to minimize potential injury to the AV node. An open antiarrhythmia procedure is frequently performed concomitantly.

D. Prognosis

Ebstein’s malformation is a rare but challenging congenital cardiac defect. The high degree of anatomic variability makes it difficult to have a standardized approach to these children. The symptomatic neonate carries a very grave prognosis. The presence of associated cardiac and other congenital anomalies often make survival impossible. Surgical options are limited at this age and often still result in a poor outcome. Medical management, if possible, is the best, as surgical success improves with age. If surgery is required, conversion to functional tricuspid atresia often offers the best survival, as the ventricle in the severely symptomatic neonate functions poorly. Transplantation remains an option, but the availability of organs limits its utility.

Patients who are not symptomatic in the neonatal period will often remain free from symptoms well into adolescence. Electrophysiologic symptoms usually precede symptoms of congestive heart failure. Indications for repair at these ages include symptoms, cyanosis, and progressive cardiomegaly.

3. Left-Sided Anomalies

Aortic Stenosis

A. General Considerations

Aortic stenosis is a form of left ventricular outflow tract obstruction that may occur at a valvar (70%), subvalvar (25%), or supravalvar (5%) level. Aortic stenosis occurs in about 4% of patients with congenital heart disease. The severity of aortic stenosis may be graded as mild (peak pressure gradient < 50 mm Hg), moderate (50 to 75 mm Hg), or severe (> 75 mm Hg).

Valvar aortic stenosis occurs secondary to maldevelopment of the aortic valve. Most commonly, a bicuspid valve is present, although tricuspid and unicuspid valves are also represented. In valvar aortic stenosis, the leaflets are thickened and frequently dysmorphic, and there is a variable degree of leaflet fusion along the commissures. The aortic annulus may be hypoplastic. In 20% of cases, valvar aortic stenosis is associated with other cardiac defects, most commonly coarctation of the aorta, PDA, VSD, or mitral stenosis. Men with valvar aortic stenosis outnumber women by a ratio of 4:1. There is a wide spectrum of clinical presentations of valvar aortic stenosis, but patients tend to present in one of two groups. Neonates and infants with severe aortic stenosis develop symptoms of rapidly progressive congestive heart failure, while older children generally have less severe obstruction and a more slowly progressive course.

Subvalvar aortic stenosis occurs below the level of the aortic valve and may be discrete (80%) or diffuse (20%). Discrete (or membranous) subaortic stenosis is rarely seen in infants and tends to progress over time. This lesion consists of a crescent or circumferential fibrous or fibromuscular membrane that protrudes into the left ventricular outflow tract. The pathogenesis of discrete subaortic stenosis is unknown, but it is thought to be an acquired lesion that develops secondary to a congenital abnormality of the left ventricular outflow tract in which abnormal flow patterns lead to endocardial injury with resultant fibrosis. Although the aortic valve leaflets are usually normal in discrete subaortic stenosis, the turbulent flow created by the obstruction can cause leaflet thickening and progressive aortic insufficiency. Diffuse subaortic stenosis is a more severe form of stenosis that creates a long, tunnel-like obstruction. Diffuse subaortic stenosis should be distinguished from hypertrophic cardiomyopathy. Both forms of subaortic stenosis are associated with a high risk of endocarditis.

Supravalvar aortic stenosis is characterized by thickening of the wall of the ascending aorta. The lesion may be localized (80%) to the region of the sinotubular ridge (at the level of the valve commissures), creating an hourglass deformity, or it may be more diffuse (20%), extending into the aortic arch and its branches. In both varieties, the aortic valve leaflets may be abnormal. The free edges of the aortic valve leaflets may adhere to the aortic wall in the region of intraluminal thickening, and this may lead to reduced coronary blood flow during diastole. Aortic wall thickening may also extend into the coronary ostia and further impair coronary blood flow. Associated cardiac lesions are common, particularly branch pulmonary artery stenoses. A genetic basis for supravalvar aortic stenosis has been established. About 50% of cases of supravalvar aortic stenosis are associated with Williams syndrome, in which a partial deletion of chromosome 7 (including the elastin gene) leads to the triad of supravalvar stenosis, mental retardation, and a characteristic “elfin” facies. Isolated mutations in the elastin gene have also been shown to produce familial supravalvar aortic stenosis with an autosomal dominant pattern of transmission. There is a significant incidence of endocarditis in patients with supravalvar aortic stenosis. Sudden death is frequently reported and is probably related to coronary obstruction.

B. Clinical Findings

Severe aortic stenosis is usually well-tolerated during fetal development. Although left ventricular output and antegrade flow across the aortic valve are decreased, the right ventricle compensates with increased output, and systemic perfusion is maintained by flow across the ductus. After birth, there is increased venous return to the left heart, and this exacerbates the pressure load created by the stenotic aortic valve, leading to left ventricular dysfunction. As the ductus closes during postnatal life, systemic malperfusion may develop with resulting hypotension, acidosis, and oliguria. Coronary perfusion is also impaired due to the combination of systemic hypotension and elevated left ventricular end-diastolic pressures. Patients with critical aortic stenosis typically exhibit severe left ventricular dysfunction. These patients usually show signs of distress soon after birth. On examination, there is impaired distal perfusion with poor capillary refill and diminished, thready pulses. A systolic ejection murmur may be absent if the cardiac output is severely diminished. Differential cyanosis may be observed due to perfusion of the lower body with desaturated blood shunting through the ductus. The electrocardiogram shows left ventricular hypertrophy, and the CXR displays cardiomegaly and pulmonary congestion. Echocardiography establishes the diagnosis.

In contrast to infants with critical aortic stenosis, older children with valvar aortic stenosis usually present with less severe stenosis (mild or moderate), and most are asymptomatic. Symptoms of angina, syncope, and congestive heart failure are not commonly reported. Congenital valvar aortic stenosis is a progressive lesion, however, and survival is dependent on the severity of stenosis and its rate of progression. Sudden cardiac death is the most common cause of mortality. Endocarditis occurs in less than 1% of patients. The diagnosis of valvar aortic stenosis in older children can frequently be made on physical examination. There is a classic systolic crescendo-decrescendo murmur at the upper sternal border, which radiates to the neck. An ejection click is often present. A visible apical impulse is suggestive of significant left ventricular hypertrophy. In severe cases, the pulse may be weak and delayed (pulsus tardus et parvus). The electrocardiogram shows left ventricular hypertrophy. The CXR is usually normal. Echocardiography accurately defines the level of stenosis and its severity. Using Doppler techniques, the pressure gradient across the stenotic valve may be estimated using a simplified form of the Bernoulli equation P = 4V², where P is the pressure gradient and V is the peak flow velocity. Cardiac catheterization is generally reserved for therapeutic intervention.

The clinical findings in subvalvar aortic stenosis are similar to those for valvar stenosis. The signs and symptoms of supravalvar aortic stenosis are similar to those in other forms of left ventricular outflow tract obstruction. The diagnosis is made by echocardiography, but cardiac catheterization or cardiac MRI is essential to define the aortic, coronary, and pulmonary arterial anatomy prior to surgical intervention.

C. Treatment

The neonate or infant with critical aortic stenosis represents a true emergency. Endotracheal intubation and inotropic support is routine. Ductal patency is maintained with prostaglandins, and acidosis is corrected. All patients with critical aortic stenosis require some form of urgent intervention. The approach is determined by the valve morphology and by the presence of associated defects. In its most extreme form, critical aortic stenosis may be associated with underdeveloped left-sided cardiac chambers and therefore may represent a form of HLHS. In these cases, single-ventricle palliation must be undertaken. For patients with adequate left-sided chambers, relief of aortic stenosis may be achieved by one of the following three approaches: percutaneous balloon valvuloplasty, surgical valvotomy, or aortic valve replacement. Balloon valvuloplasty is generally considered the procedure of choice when the aortic valve annulus is adequate and there are no associated cardiac defects. Alternatively, surgical valvotomy may be accomplished by closed or open techniques. The closed approach is performed using cardiopulmonary bypass without aortic cross-clamping. Dilators of increasing size are passed through a ventriculotomy in the left ventricular apex and advanced across the aortic valve. Some centers prefer open surgical valvotomy, which allows a precise valvotomy under direct vision, although aortic cross-clamping with cardioplegia is necessary. In all cases, the goal of therapy is to relieve stenosis without creating excessive aortic insufficiency. Dramatic clinical improvement is expected following balloon or surgical valve valvotomy, and early survivals of greater than 80% have been reported. The incidence of aortic insufficiency is slightly higher following balloon valvotomy. In most cases, however, stenosis will recur and repeat valvotomy or aortic valve replacement will eventually be required. Aortic valve replacement is problematic in the neonate due to small patient size. In these cases, many consider the best valve replacement to be a pulmonary autograft (Ross procedure) with enlargement of the aortic annulus (Konno aortoventriculoplasty). The Ross–Konno procedure has been used successfully for neonates with critical aortic stenosis in whom the aortic annulus is hypoplastic and for selected patients in whom valvuloplasty was unsuccessful. Survival following the Ross-Konno procedure in infants has been shown to be excellent. Growth of the pulmonary autograft has been documented, thereby making it an ideal valve replacement for children. Unfortunately, as part of the Ross procedure, the pulmonary valve must be replaced using a cryopreserved homograft, which does not grow, and homograft replacement must be anticipated at intervals as the patient grows.

All patients with severe valvar aortic stenosis should undergo intervention, as should all symptomatic patients with moderate stenosis. Asymptomatic patients with mild or moderate stenosis are generally observed. As described for critical aortic stenosis, the techniques used to relieve aortic stenosis in older patients include percutaneous balloon valvuloplasty, surgical valvulotomy, and valve replacement. Balloon valvuloplasty is usually performed as the primary intervention and is associated with a success rate of nearly 90% and a mortality of less than 1%. Open surgical valvotomy is an alternative approach with similar results. For valves that are severely dysplastic, develop restenosis after intervention, or become insufficient as a result of prior intervention, valve replacement may be necessary. For older children, there are more options for valve replacement. The choices include mechanical prostheses, bioprosthetic valves, and tissue substitutes, such as porcine xenografts, cryopreserved human allografts, and pulmonary autografts (Ross procedure). The mechanical valves are the most durable but require chronic anticoagulation. The bioprosthetic and tissue valves do not require long-term anticoagulation but tend to deteriorate over time (with the exception of the pulmonary autograft). The pulmonary autograft has the potential advantage of growth but the homograft used to replace the pulmonary valve will require replacement. Selection of the appropriate replacement valve is a complex decision requiring input from all involved parties.

Intervention for discrete subvalvar stenosis is usually undertaken when the gradient exceeds 30-50 mm Hg or when aortic insufficiency is present. In these patients, resection of the membrane is readily performed by a transaortic approach. In order to reduce the incidence of restenosis, many centers advocate concurrent performance of a septal myomectomy to alter the geometry of the left ventricular outflow tract.

When diffuse subaortic stenosis is associated with hypoplasia of the aortic annulus, repair is best achieved with a Konno aortoventriculoplasty, whereby an incision is carried across the aortic annulus and subjacent ventricular septum, the opening patched, and an aortic valve implanted. Patients with an adequate aortic annulus may undergo a septoplasty (modified Konno), in which the septal incision is confined to the immediate subvalvar area and a patch is used to widen the left ventricular outflow tract without replacing the aortic valve.

Operative intervention is indicated for patients with supravalvar aortic stenosis in whom the gradient exceeds 50 mm Hg. A number of operations have been proposed for the treatment of localized supravalvar stenosis. The classical repair involves a longitudinal incision across the obstruction in the ascending aorta, which is extended into the noncoronary sinus. The thickened, hypertrophic ridge is resected by endarterectomy, and the aortotomy is augmented with an elliptical patch. A variation of this repair involves creation of an inverted-Y aortotomy with one limb of the Y extended into the noncoronary sinus and the other into the right coronary sinus. A Y-shaped patch is then used to augment the aortotomy. Finally, the Brom repair is performed by transection of the ascending aorta beyond the supravalvar ridge. Separate incisions are then made through the supravalvar ridge into each sinus of Valsalva. Triangular patches are placed to augment each of these incisions, thereby relieving the supravalvar obstruction. Reconnection of the aortic root to the ascending aorta completes the repair. The repair of the diffuse type of supravalvar stenosis is performed under circulatory arrest with extensive patching of the ascending aorta, transverse arch, and involved arch arteries. Branch pulmonary stenoses are best managed using transcatheter techniques.

D. Prognosis

Operative mortality approaches zero for resection of discrete subaortic stenosis. The recurrence rate of discrete stenosis following membrane resection and myomectomy has been reported to be as low as 4%. Despite the technical complexity of repair of diffuse subaortic stenosis, excellent results have been reported with high survival and freedom from reoperation. The results of surgery for localized supravalvar aortic stenosis are generally good with low operative mortality and excellent long-term survival. The diffuse form is more difficult to treat, and recurrence is more likely. Overall results are much worse when severe bilateral pulmonary artery stenoses are present. The mortality for aortic valve replacement regardless of valve choice is 2%-5%. The need for reoperation is dependent on valve choice and patient size. Early and late ventricular arrhythmias may occur commonly in patients with significant left ventricular hypertrophy.

Aortic Coarctation

A. General Considerations

Coarctation of the aorta is a narrowing of the proximal descending thoracic aorta distal to the origin of the left subclavian artery, near the insertion of the ductus arteriosus (or ligamentum arteriosum). The severity of luminal narrowing and the length of the aorta affected are variable. Coarctation is thought to occur as a result of ectopic tissue from the ductus arteriosus that migrates into the wall of the adjacent aorta. After birth, as the ductus closes, the ectopic tissue in the aorta also constricts. Frequently, a posterior shelf of tissue is present at the point of most severe obstruction. The aortic obstruction caused by coarctation creates a pressure load on the left ventricle.

The incidence of coarctation is about 0.5 per 1000 live births, and its prevalence is about 7% of congenital heart defects. Coarctation is commonly associated with other heart defects, including bicuspid aortic valve (in more than 50% of cases), PDA, and VSD. Other left-sided obstructive lesions may also be present, such as aortic arch hypoplasia, aortic stenosis, mitral stenosis, and left ventricular hypoplasia. Coarctation is also recognized to occur in association with Turner syndrome.

B. Clinical Findings

Patients with severe coarctation present in the newborn period. Aortic obstruction is so significant that perfusion of the lower body is dependent upon flow from the ductus arteriosus. Spontaneous ductal closure typically worsens the aortic obstruction and may lead to malperfusion of tissues distal to the coarctation. The pressure load on the left ventricle may precipitate congestive heart failure. Patients may develop shock with severe acidosis, oliguria, and diminished distal pulses. Infants with severe coarctation will generally not survive without intervention.

Older children with coarctation are usually asymptomatic. The diagnosis is commonly made on the basis of hypertension in the upper extremities with decreased pulses in the lower extremities. Noninvasive blood pressure measurements in all four extremities help to quantify the severity of aortic obstruction. Older patients tend to develop extensive collateral arteries that bypass the obstruction. Life expectancy for these patients is 34 years without operation typically due to the development of heart failure. Other long-term complications of coarctation include aortic dissection (21%), endocarditis (18%) (frequently involving a bicuspid aortic valve), intracranial hemorrhage (12%) (from Berry aneurysms, which occur more commonly in patients with coarctation), endarteritis (in the poststenotic area of the aorta at the site of the jet of turbulent flow), and aortic aneurysm.

The diagnosis of coarctation can usually be made clinically. The infant with significant coarctation is frequently asymptomatic at birth but following closure of the ductus develops signs of heart failure such as irritability, tachypnea, and poor feeding. Lower extremity pulses are absent, and upper extremity pulses may be weak. Chest radiography shows cardiomegaly and pulmonary venous congestion. There is a left ventricular strain pattern on the electrocardiogram. Echocardiography is usually diagnostic, demonstrating narrowing of the aorta at the coarctation site with a loss of pulsatility in the descending aorta.

In older children and adults with coarctation, a pressure gradient between the arms and legs usually can be demonstrated by measuring cuff pressures in all four extremities. On chest radiography, rib notching may be evident, secondary to erosion of the inferior rib borders from the development of large intercostal collateral vessels. Echocardiography usually confirms the diagnosis. Anatomic details may also be clarified with CTA and cMRI. Cardiac catheterization is usually not necessary.

C. Treatment

Generally, all patients with coarctation should undergo surgical repair if the gradient is greater than 20 mm Hg. For neonates, the acute medical management includes initiation of PGE₁ for the purpose of reopening the ductus; this maneuver partially relieves the aortic obstruction and augments perfusion of the lower body due to improved antegrade flow across the arch as well as right-to-left flow across the ductus. Prostaglandins are usually effective for reopening the ductus when initiated within 3-7 days of life but are less successful thereafter.

Surgical repair of coarctation is usually performed through a left posterolateral thoracotomy via the third or fourth intercostal space. The descending thoracic aorta, ductus (or ligamentum), transverse aortic arch, and brachiocephalic vessels are mobilized. Care is taken to preserve the vagus nerve and its recurrent laryngeal branch.

The coarctation is usually evident externally by narrowing or posterior indentation; however, the degree of internal narrowing is usually much more severe. A dose of heparin (100 units/kg) may be given intravenously for patients younger than 2 years. Proximal and distal control of the aorta is achieved using clamps. Usually, the proximal clamp is positioned on the transverse arch between the innominate and left carotid vessels with concomitant occlusion of the left carotid and left subclavian. In infants and children, the preferred surgical approach to coarctation is resection with extended end-to-end repair. A generous resection of the coarctation segment is performed. The proximal aorta is then spatulated along the lesser curvature and the distal aorta along the greater curvature. An extended end-to-end anastomosis is then performed.

In older children and adults, it may not be possible to perform a resection with primary repair without creating excessive tension on the anastomosis, which may lead to hemorrhage or scarring with recurrent coarctation. An alternative strategy is necessary in these cases. Patch aortoplasty may be performed in children in whom further growth is anticipated. The subclavian flap repair augments the narrowed aorta using native arterial tissue. Blood flow to the left arm is maintained by collateral vessels, although long-term studies have demonstrated a slight discrepancy in limb length in some patients. Prosthetic patch material may also be used. By avoiding circumferential prosthetic material, growth potential of the native aorta is preserved. The disadvantage of patch repair is a high risk of aneurysm formation. In adults, where growth is no longer an issue, resection of the coarctation may be performed with subsequent placement of a prosthetic interposition graft (either Dacron or polytetrafluoroethylene).

One of the principal concerns during coarctation repair is interruption of distal aortic blood flow, especially to the spinal cord. The anterior spinal artery is fed by major radicular branches from intercostal arteries. In patients without well-formed collaterals, ischemia of the spinal cord may be precipitated by aortic cross-clamping, and paraplegia may result. Protective measures include induction of mild hypothermia, maintenance of a high proximal aortic pressure, and minimization of cross-clamp time. In older patients, distal aortic perfusion may be maintained by the technique of left heart bypass, where oxygenated blood is taken from the left atrium and delivered to the femoral artery or distal aorta using a centrifugal pump. Overall, the incidence of paraplegia following coarctation repair is less than 1%.

Transcatheter therapy has been proposed for the primary therapy of coarctation, but this approach is controversial due to the incidence of recurrent coarctation, need for multiple interventions, injury to the femoral vasculature (for access), and aneurysm formation. Improved results have been achieved with balloon angioplasty with concurrent stent placement in older children and adults in whom further aortic growth is not anticipated. Balloon angioplasty is widely accepted for the treatment of recurrent coarctation following surgery, with 88%-94% achieving a gradient less than 20 mm Hg.

D. Prognosis

The early mortality following repair of coarctation in neonates is 1%-3%, while the risk in older children and adults is about 1%-2%. The incidence of recurrent coarctation following resection and end-to-end repair is about 10% whereas catheter-based interventions are associated with reintervention rates of 25% for balloon angioplasty and 5%-40% for stent placement. The long-term survival following repair of coarctation is determined by the presence of associated defects and the persistence of hypertension.

Following repair, patients may develop severe hypertension. This can be managed using intravenous beta-blockers (eg, esmolol) or vasodilators (eg, sodium nitroprusside). Uncontrolled hypertension can lead to the complication of mesenteric arteritis. Hypertension usually resolves within days to weeks after repair, although older children and adults may require lifelong antihypertensive therapy. Repair of coarctation during infancy is thought to minimize the risk of late hypertension.

Vascular Rings

A. General Considerations

Vascular rings comprise a spectrum of vascular anomalies of the aortic arch, pulmonary artery, and brachiocephalic vessels. The clinically significant manifestation of these lesions is a varying degree of tracheoesophageal compression. These vascular anomalies can be divided into complete vascular rings and partial vascular rings. Complete vascular rings can be divided into double aortic arch and right aortic arch with left ligamentum arteriosum. These two categories can be further subdivided on the basis of the specific anatomy. Incomplete vascular rings include aberrant right subclavian artery, innominate artery compression, and pulmonary artery sling. Other rare variations, which have been described, include left aortic arch with right descending aorta and right ligamentum, and left aortic arch with aberrant right subclavian artery and right ligamentum. The incidence of clinically significant vascular rings is 1%-2% of all congenital heart defects.

Vascular rings and pulmonary slings have been described in conjunction with other cardiac defects, including, TOF, ASD, branch pulmonary artery stenosis, coarctation, AVSD, VSD, interrupted aortic arch, and aortopulmonary window. Significant associated cardiac anomalies occur in 11%-20% of patients with a vascular ring. A right aortic arch is generally associated with a greater incidence of coexisting anomalies.

By the end of the fourth week of embryonic development, the six aortic or branchial arches have formed between the dorsal aortae and ventral roots. Subsequent involution and migration of the arches results in the anatomically normal or abnormal development of the aorta and its branches. The majority of the first, second, and fifth arches regress. The third arch forms the common carotid artery and proximal internal carotid artery. The right fourth arch forms the proximal right subclavian artery. The left fourth arch contributes to the portion of the aortic arch from left carotid to left subclavian arteries. The proximal portion of the right sixth arch becomes the proximal portion of the right pulmonary artery, while the distal segment involutes. Similarly, the proximal left sixth arch contributes to the proximal left pulmonary artery, and the distal sixth arch becomes the ductus arteriosus.

The pulmonary artery is formed from two vascular precursors as well as through a combination of angiogenesis, the de novo development of new blood vessels, and vasculogenesis, the budding and migration of existing vessels. As stated previously, the proximal pulmonary arteries are based on the sixth arches, whereas the primitive lung buds initially derive their blood supply from the splanchnic plexus. Ultimately, these two segments of the pulmonary artery join to form the vascular network of the lung parenchyma.

B. Clinical Findings

Children with a complete vascular ring generally present within the first weeks to months of life. Typically, children with a double aortic arch present earlier in life than those with a right arch and retroesophageal left ligamentum. In the younger age group, respiratory symptoms predominate, as liquids are generally well tolerated. Respiratory symptoms may include stridor, nonproductive cough, apnea, or frequent respiratory infections. The cough is classically described as “seal bark,” or “brassy.” These symptoms may mimic asthma, respiratory infection, or reflux, and children with vascular rings are often initially misdiagnosed. With the transition to solid food, dysphagia becomes more apparent.

The presentation of a patient with an incomplete vascular ring is variable. Children with innominate artery compression usually present within the first 1-2 years of life with respiratory symptoms. Although, aberrant right subclavian artery is the most common arch abnormality, occurring in approximately 0.5%-1% of the population, it rarely causes symptoms. Classically, when symptoms do occur, they present in the seventh and eighth decade, as the aberrant vessel becomes ectatic and calcified, causing dysphagia lusoria due to impingement of the artery on the posterior esophagus. An aberrant right subclavian rarely causes symptoms except when it is of an abnormally large caliber or associated with tracheomalacia.

Children with pulmonary artery slings generally present with respiratory symptoms within the first few weeks to months of life. As with complete rings, respiratory symptoms may include stridor, nonproductive cough, apnea, or frequent respiratory infections and may mimic other conditions leading to misdiagnosis. Pulmonary artery slings are associated with complete tracheal rings in 30%-40% of patients, leading to focal or diffuse tracheal stenosis.

The methods for diagnosing a vascular ring are multiple because of the variability in presentation and the spectrum of diagnostic tests available. A child with a presumptive diagnosis of asthma or tracheomalacia may be referred to a pulmonologist and a diagnosis of vascular ring made or suspected initially by CXR and bronchoscopy. In some situations, the diagnosis is made by echocardiography during evaluation for concurrent cardiac defects. Regardless, the diagnosis generally begins with a CXR. Complementary studies may include barium esophagogram, CTa, cMRI, and bronchoscopy. Important modalities to define the tracheal anatomy in a patient with a pulmonary artery sling include CTA, cMRI, or bronchoscopy. Echocardiography may be diagnostic and may be used to rule out other cardiac anomalies. Tracheograms and cardiac catheterizations, which have been used extensively in the past, are rarely currently indicated.

C. Treatment

A double aortic arch occurs when the distal portion of the right dorsal aorta fails to regress. The two arches form a complete ring, encircling the trachea and esophagus. The right arch is dominant in the majority of the cases, followed by left dominant, with codominant arches being the least common. The left and right carotid and subclavian arteries generally arise from their respective arches. The ligamentum arteriosum and descending aorta usually remain on the left.

The approach to repair of a double aortic arch is via a left posterolateral thoracotomy. The procedure can easily be accomplished through a limited, muscle-sparing incision through the third or fourth intercostal space. The pleura is incised, after identifying the vagus and phrenic nerves. The ligamentum or ductus arteriosum is divided while preserving the recurrent laryngeal nerve. The nondominant arch is then divided between two vascular clamps at the point where brachiocephalic flow is optimally preserved. If there is concern regarding the location for division, the arches can be temporarily occluded at various points while monitoring pulse and blood pressure in each limb. If there is an atretic segment, the division is done at the point of the atresia. Dissection around the esophagus and trachea in the region of the ligamentum/ductus and nondominant arch allows for retraction of the vascular structures and lysis of any residual obstructing adhesions.

There are three anatomic variations for a right arch with a left ligamentum, which cause a complete vascular ring. If the left fourth arch regresses between the aorta and left subclavian, a right aortic arch with aberrant left subclavian artery results. The ligamentum arteriosum is retroesophageal, bridging the left pulmonary artery and aberrant left subclavian, forming a complete vascular ring. If the left fourth arch regresses after the origin of the left subclavian artery but before the arch reaches the dorsal aorta to communicate with the left sixth arch (which becomes the ductus arteriosum), there is mirror-image branching. The ligamentum arteriosum arises directly from the descending aorta, or from a Kommerell diverticulum off of the descending aorta, forming the complete ring. If communication is maintained between the left fourth and sixth arches, there is mirror-image branching with the ligamentum arising from the anterior, mirror-image left subclavian, and a ring is not formed.

The surgical approach for a right aortic arch with retroesophageal left ligamentum arteriosum is the same as for a double arch. The ligamentum is divided, and any adhesions around the esophagus and trachea are lysed. Rarely, the Kommerell diverticulum has been reported to cause compression even after division of the ligamentum. As such, it may be prudent to resect or suspend the diverticulum posteriorly.

In innominate artery compression syndrome, the aortic arch and ligamentum are in their normal leftward position. However, the innominate artery arises partially or totally to the left of midline. As the artery courses from left to right anterior to the trachea, it causes tracheal compression. The symptoms of innominate artery compression may be mild to severe. With mild symptoms and minimal tracheal compression on bronchoscopy, children can be observed expectantly because the symptoms may resolve with growth. Indications for surgery include apnea, severe respiratory distress, significant stridor, or recurrent respiratory tract infection. Several approaches for the correction of innominate artery compression syndrome have been described. These include simple division, division with reimplantation into the right side of the ascending aorta, and suspension to the overlying sternum.

An aberrant right subclavian artery occurs when there is regression of the right fourth arch between the right common carotid and right subclavian arteries. The right subclavian then arises from the leftward descending aorta, laying posterior to the esophagus as it crosses from left to right. Although the artery can compress the esophagus posteriorly, it is rarely the cause of symptoms in children. Surgical treatment involves simple division via a left posterolateral thoracotomy. Rarely, reimplantation or grafting from the right carotid or aortic arch may be necessary.

Normally, the right and left sixth aortic arches contribute to the proximal portions of their respective pulmonary arteries. If the proximal left sixth arch involutes and the bud from the left lung migrates rightward to meet the right pulmonary artery, a pulmonary artery sling is formed. Pulmonary artery slings are associated with complete tracheal rings and tracheal stenosis in 30%-40% of patients. Origin of the right upper lobe bronchus from the trachea (“pig bronchus” or “bronchus suis”) has been reported in frequent association with pulmonary artery sling.

Initial attempts at the repair of a pulmonary artery sling involved reimplantation after division of the left pulmonary artery and translocation of the trachea without cardiopulmonary bypass. These early reports had a high incidence of left pulmonary artery thrombosis. This has led some authors to advocate division of the trachea and translocation of the left pulmonary artery. This approach would seem sensible if the trachea were being divided in the course of tracheal reconstruction. However, currently most authors advocate the reimplantation of the left pulmonary artery, which has resulted in excellent results. The procedure is done via a median sternotomy on cardiopulmonary bypass to insure optimal visualization of the repair. Aortic cross-clamping is not necessary. The left pulmonary artery is divided off of the right pulmonary artery, translocated anterior to the trachea, and reimplanted into the main pulmonary artery.

Any necessary reconstruction of the trachea for complete tracheal rings is done concurrently with bronchoscopic assistance. Many techniques for tracheal reconstruction have been described, with resection and primary reanastomosis and sliding tracheoplasty offering the most reliable results.

Over 95% of vascular rings without concurrent cardiac defects can be performed through a left thoracotomy. A right thoracotomy is indicated for the rare cases where there is a right ligamentum arteriosum. A right ligamentum occurs in the setting of a left aortic arch with right descending aorta, where the ligamentum bridges from the descending aorta to the right pulmonary artery forming a complete ring. Right ligamentum arteriosum has also been described with a left aortic arch with aberrant right subclavian artery. In this case, the ligamentum may arise from the aberrant subclavian artery, from a diverticulum off of the arch, or directly from the left arch to the right pulmonary artery. In addition, a double aortic arch with an atretic segment proximal to the right carotid artery is more easily divided through a right thoracotomy. The approach to these anomalies is the same as for a left-sided ring division, with the caveat that the right recurrent laryngeal nerve will loop around the right ligamentum.

Repair of vascular rings has been described using video-assisted thoracoscopic surgery (VATS) both with and without robotic assistance. Candidates for thoracoscopic division are limited to those patients requiring only the division of nonpatent vascular structures. In general, VATS is used for patients weighing more than15 kg due to current size limitations of the instruments.

D. Prognosis

Hospital mortality for the repair of a vascular ring was 1.6% in a recent series of 183 patients by Ruzmetov and colleagues. Overall survival was 96% at 35 years. Eight patients were repaired utilizing left pulmonary artery division and reimplantation for pulmonary artery sling, three of whom also required cardiopulmonary bypass for tracheal reconstruction. Of the 183 patients there were no operative mortalities and eight late deaths. All deaths were in patients with other complex cardiac anomalies. The major source of morbidity, as well as mortality, in this and other series is related to the tracheal reconstruction.

Coronary Anomalies

A. General Considerations

Coronary artery anomalies occur in between 0.2% and 1.2% of the population. They can be classified as minor, secondary, or major on the basis of their clinical significance. Minor defects have no functional significance and are usually detected as incidental findings at cardiac catheterization. Secondary defects have no intrinsic significance but alter surgical management when they are present. An example of a secondary defect is an anomalous origin of the left anterior descending from the right coronary artery, which crosses the hypoplastic infundibulum in a patient with TOF. The presence of this vessel may prevent the safe performance of a transannular incision and thereby mandate the use of a conduit. Major defects are the most important form of coronary anomaly because they exert an intrinsically adverse effect on the myocardium. Major anomalies can be subdivided based on anatomy: coronary arteriovenous fistula, anomalous pulmonary origin of a coronary artery, anomalous aortic origin of a coronary artery, myocardial bridging, or coronary artery aneurysm.

Coronary arteriovenous fistula is the most common major coronary anomaly. An abnormal connection exists between a coronary artery (usually the right) and another vascular structure (usually one of the right heart chambers). Most fistulas are isolated and solitary. The fistula leads to left-to-right shunting, which can produce congestive heart failure. Other symptoms include angina, endocarditis, myocardial infarction, arrhythmia, and sudden death. The diagnosis is suggested by echocardiography and confirmed by catheterization.

The second-most common major coronary anomaly is the origin of a coronary artery from the pulmonary artery. The most common manifestation is the anomalous left coronary artery arising from the pulmonary artery (ALCAPA). The right coronary (or both coronaries) may also arise anomalously from the pulmonary artery but only in very rare cases. ALCAPA is usually well tolerated during fetal development, but after birth, the pulmonary systolic pressure usually drops (following ductal closure and decline in PVR) and the anomalous coronary is perfused with desaturated blood at low pressure. Collateral vessels develop between the normal right coronary artery and the abnormal left coronary, but the benefit is negated due to the development of coronary steal, whereby the collateral blood shunts left to right by retrograde flow in the anomalous coronary into the low-pressure pulmonary artery. Most patients will present between 6 weeks and 3 months of life. Typical symptoms include irritability, difficulty in feeding, and other signs of congestive heart failure. Untreated, ALCAPA is nearly always fatal. Rarely, patients will survive to adulthood and present with symptoms of angina or sudden death. On examination, patients with ALCAPA frequently have a holosystolic murmur of ischemic mitral regurgitation. The pulmonary component of the second heart sound may be pronounced because of pulmonary hypertension. Chest radiography is significant for cardiomegaly and pulmonary edema. Electrocardiographic evidence of ischemia and infarction is usually present. Echocardiography is usually diagnostic and is useful for assessing the severity of left ventricular dysfunction and ischemic mitral regurgitation that are commonly present. Catheterization is occasionally necessary to clarify the anatomy, but this technique is used less frequently because of the risk of inducing life-threatening arrhythmias.

Anomalous aortic origins of the coronary arteries are usually minor defects, but a potentially dangerous abnormality exists when the left main coronary artery arises from the right coronary sinus and passes between the pulmonary artery and aorta. This defect has been associated with cardiac symptoms and sudden death, as has the origin of the right coronary artery from the left coronary sinus (usually when the right coronary is dominant). The etiology of ischemia in both defects is thought to be related to the acute angle of origin and slit-like orifice of the anomalous vessel and the extrinsic compression created by the apposing walls of the aorta and pulmonary artery. These defects usually present in older patients. Symptomatic patients are treated surgically by coronary artery bypass.

Myocardial bridging occurs when a segment of an epicardial coronary artery (usually the left anterior descending) takes an intramyocardial course over a short segment. Although this is a common incidental finding at cardiac catheterization, this defect has been associated in some cases with myocardial ischemia. Treatment involves dividing the muscle bridge to free the coronary, coronary bypass beyond the bridge, or transcatheter stenting.

Coronary aneurysms occur rarely, usually in conjunction with an inflammatory condition such as Kawasaki syndrome, polyarteritis nodosa, Takayasu arteritis, or syphilis. Coronary aneurysms may thrombose or lead to distal coronary stenosis or embolization. Rupture occurs uncommonly. Treatment ranges from antiplatelet therapy to coronary artery bypass grafting, and possible transplantation.

B. Treatment

All symptomatic fistulas should be occluded, either surgically or by transcatheter techniques. In some cases, coronary bypass grafting may be necessary when distal flow is compromised by fistula occlusion. Treatment of asymptomatic fistulas is controversial, but occlusion should probably be undertaken when significant left-to-right shunting is present.

Surgical repair is indicated for all patients with ALCAPA. Historically, the initial surgical approach involved ligation of the proximal left coronary artery. This served to eliminate coronary steal and allow perfusion of the left coronary system by collaterals from the right. Despite the ease of simple ligation, most centers have abandoned this approach in favor of establishment of a 2-coronary system, which offers better long-term freedom from ischemia. In older patients, this may be achieved by proximal ligation of the left coronary artery in conjunction with coronary artery bypass, ideally with a left internal mammary graft. Coronary bypass is technically difficult in neonates, and a number of alternative operations have been devised to create a direct connection between the aorta and the anomalous coronary artery. Most commonly, this can be achieved by removing the origin of the left coronary artery (along with a button of adjacent pulmonary artery) and reimplanting the vessel directly into the side of the aorta. Another approach involves creation of a side-to-side connection between the aorta and pulmonary artery with placement of an intrapulmonary baffle to direct flow from this connection to the anomalous left coronary ostium.

C. Prognosis

Survival following surgical repair of ALCAPA has improved over the years. Recent reports have suggested an operative mortality of 0%-6%. Ventricular function tends to normalize after surgery. In most patients, mitral valve function also improves, but for patients with severe mitral regurgitation, concurrent mitral valve repair may be indicated.