Chapter 25. Minimally Invasive Myocardial Revascularization

The term minimally invasive coronary artery bypass grafting is not well defined. According to one definition, avoidance of cardiopulmonary bypass (CPB) is considered essential in decreasing the morbidity associated with conventional coronary artery bypass grafting (CABG).1 Other authors consider the median sternotomy as a potential source for morbidity, referring to the risk of mediastinitis and the associated delayed return to daily life activities.2 Accordingly, a number of surgical strategies have evolved to avoid the need for extracorporeal circulation and to minimize surgical access. Furthermore, operative strategies as avoidance of aortic manipulation or complete arterial revascularization focus on improved short- and long-term results. At the same time, it was widely recognized that open harvesting techniques for bypass grafts often are associated with wound-healing problems, especially in diabetic patients. As a consequence, endoscopic harvesting techniques for both venous and radial artery grafts have been developed.

For decades, CABG was routinely performed with cardioplegic arrest and using CPB. An empty, nonbeating heart, a bloodless surgical field, and an easy exposure were regarded as essential for success of the procedure. Results were excellent, mortality declined constantly, and standard CABG became the "bread and butter" of our profession.3 Anecdotal reports on the deleterious effects of CPB and systematic reports examining the pathophysiology of extracorporeal circulation started to question the dogma of "the pump is your friend." CPB is associated with (1) a systemic inflammatory response, (2) release of cytokines, (3) activation of the clotting cascade, (4) metabolic changes, (5) microembolization and numerous other adverse effects. Although tolerated in most cases, these effects alone or in combination may cause substantial morbidity and thus affect the results of the procedure. With an ever-aging population and increasing comorbidity, surgeons all over the world sought to further minimize the risk of CABG, and it seemed logical to question the role of CPB in CABG.

The evolution of off-pump coronary artery bypass grafting (OPCAB) is closely linked to the development of stabilizers that became available in the early 1990s. Initially, pure pressure stabilizers were engineered, but it soon became obvious that exposure of the back wall of the heart would require additional means of support. With the introduction of vacuum-assisted stabilizers by the Utrecht group, local myocardial immobilization was greatly facilitated and independent of the area of revascularization and OPCAB gained popularity. Despite better stabilizers, it was recognized that OPCAB requires a team approach and awareness of the sudden hemodynamic changes that may occur during the procedure.

Anesthesia Requirements

In most centers, general anesthesia is applied, and the patient is intubated. Incidental reports indicate that the operation is also possible on the awake, spontaneously breathing patient under high epidural anesthesia.4 Standard monitoring is applied. In addition, some centers prefer online cardiac output measurement using the PICCO or similar methods.5 A Swan-Ganz catheter is usually not helpful and can potentially cause arrhythmia when the heart is manipulated during the procedure. It is of utmost importance that the patient is kept warm at all times during the procedure. Temperature management includes placing the patient on a warming blanket, using warm infusions, and keeping the room temperature high. Volume management is essential because it is the preferred means for counterbalancing hemodynamic changes. Exposure of the back wall of the heart usually causes some degree of right ventricular outflow obstruction that can be treated adequately by increasing venous return by tilting the operating room table to the right with the head low. Because no CPB is used and filtering is not possible, intravenous volume overload must be avoided, especially in end-stage renal failure (ESRF) patients. The use of inotropes should be reserved for those with severe hemodynamic alterations only because they invariably increase the heart rate and thus complicate the procedure. In a review of human factors associated with manual control and tracking, it was pointed out that the human operator can at his or her best track a three-dimensional (3D) motion (such as the beating heart) only up to a frequency of 1 Hz, which happens to equal a heart rate of 60 beats per minute.6 Higher frequencies cannot be tracked, thus the preferred heart rate should be kept in the range of 50 to 70 beats per minute to simplify suturing. In case of atrial fibrillation, pharmacologic slowing of the heart rate and temporary ventricular pacing using an epicardial pacing wire may facilitate the procedure. The use of a Cell Saver is recommended to minimize the risk for blood transfusion, which is rarely necessary. If less than 500 mL is collected, the blood usually is discarded.

Surgical Technique

After standard median sternotomy, single or bilateral internal thoracic artery (ITA) harvesting is performed. The patient is heparinized (150 to 200 units/kg, ie, about half of CPB dosage), keeping the activated clotting time (ACT) at a level above 300 seconds. In order to facilitate exposure of the heart, it is recommended to divide the pericardial and mediastinal attachments. Opening of the right pleura may become necessary in severely dilated hearts and some surgeons do it routinely to give the heart space during tilting, allowing easier access of the posterolateral wall. After the pericardium is opened, pericardial stay sutures are placed to aid in exposure of the heart. Numerous methods have been proposed for placing these sutures. Ideally, two or more sutures are placed beginning at the level of the right upper pulmonary vein all the way down distally to the lowest point of the epicardial sac (Fig. 25-1). To avoid damage to the myocardium, the sutures should be covered by plastic tubing; sponges may be used alternatively. Placement of the stay sutures should be done slowly because abrupt changes in positioning of the heart may cause undesired hemodynamic alterations or arrhythmia. The sequence for the grafts depends largely on the individual needs of the patient. In general, the left anterior descending (LAD) artery is the most important target vessel and the easiest to bypass. Therefore, revascularization should start with an ITA graft to the LAD. By lifting the stay sutures, the LAD comes easily into view. The stabilizer is placed at the site of the anastomosis, and dissection of the surrounding tissue is begun. If the vessel is covered by excessive fat or muscle, low-energy cautery and clipping of epicardial veins may help to ensure minimal bleeding from the surrounding tissue. Once the site for the anastomosis is identified, the stabilizer is placed in a way to ensure enough space for suturing and equal distance to the stabilizer feet. Mechanical compromize of large diagonal branches should be avoided. Vacuum stabilizers should be locked only after vacuum is applied and the stabilizer sucks to the surface. Only a small amount of pressure will then be required to immobilize the heart. Excess pressure from the stabilizer will cause increasing wall motion as the heart works with more force against its compression. Temporary occlusion of the target vessel can be achieved in many ways. Surrounding 4-0 felt-pledgeted sutures or silastic tapes are used widely. The occlusion tapes ought to be placed at a distance of at least 5 to 10 mm from the anastomosis to avoid compression and distortion of the target vessel at the level of the anastomosis and thus allow for easy suturing. The suture needs to be placed deep enough in the tissue to avoid damage of the target vessel. The corresponding coronary vein should be respected to avoid disturbing side bleedings. Distal coronary artery occlusion should be avoided in general and is rarely necessary even in occluded vessels with strong backflow. Care must be taken to stay outside stented areas because the occlusion tapes may bend or kink an implanted stent. The incision usually is made before the occlusion suture is tightened to ensure complete filling of the vessel, which will minimize the risk of back wall injury. The suture then is tightened gently until bleeding stops. If there is only minimal coronary blood flow, eg, in chronic total vessel occusion, tightening may not at all be necessary. A CO2 blower-mister is used to control residual bleeding from septal branches of the distal coronary at a rate not exceeding 5 L/min. Excessive blowing can cause dissection or injury to the intima of both the graft and the coronary artery or cause air embolism. The use of coronary artery shunts is controversial because they also may cause endothelial damage. If shunts are used, care must be taken to ensure atraumatic placement. A very new development is a transparent reverse thermosensitive gel (LeGoo, Pleuromed Inc., Woburn, MA) which can be injected after incision of the coronary vessel for temporary blockage of the blood flow allowing an almost bloodfree anastomotic site. The anstomosis can then be sutured without the need for a blower-mister, shunts, or occlusion snares. The gel completely dissolves with time (after approximately 15 minutes) or with the application of local cold.7,8

The circumflex artery and its branches are grafted next in a sequence that is dictated mainly by the individual coronary pathology and the preference of grafts. The distal circumflex artery is regarded as the most challenging vessel to graft during OPCAB because exposure may be difficult. In large hearts and more importantly in patients with right ventricular dysfunction, it may be necessary to open the right pleura and divide the right-sided pericardium low to the level of the phrenic nerve. This will allow displacement of the heart underneath the sternum into the right pleural cavity. This maneuver minimizes right outflow tract obstruction and exposes all posterior vessels. After the circumflex artery, the right coronary artery (RCA) and its branches are grafted. If the RCA is the dominant vessel and the stenosis is less than 80%, it may be necessary to use a shunt because ischemia of the atrioventricular (AV) nodal artery during occlusion of the RCA can cause acute total AV block. It is therefore advisable to place and connect a temporary pacing wire before occluding the vessel.

To maximize both the short- and long-term benefit of an OPCAB procedure, arterial grafting is preferred. This will obviate the need for aortic clamping, another source for emboli and independent predictor of stroke.9 In fact, some authors see avoidance of aortic manipulation as the key factor to bring the stroke risk of CABG below the stroke risk of PCI (Table 25-1).

If vein grafts are used, the proximal or distal anastomosis can be performed first. It is of utmost importance to partially clamp the aorta under low pressure to minimize the risk of aortic embolie and to avoid aortic dissection. This can be achieved medically or by a brief period of inflow occlusion by manually compressing the inferior vena cava. This maneuver also should be repeated for declamping. Intraoperative graft patency control using transient-time Doppler or other means is recommended. If the operative field is dry, heparin usually is not completely antagonized. Postoperatively, aspirin is begun on the day of operation.

Special Situations

In patients with unstable angina, acute cardiogenic shock, or with ejection fraction (EF) below 20%, the preoperative implantation of an intra-aortic counterpulsation pump (IACP) may be useful. Alternatively these patients can be operated on-pump beating heart to combine the advantages of preserved native coronary blood flow, deloading the heart and adequate organ perfusion.14,15 Patients with atrial fibrillation (AF) show an irregular contraction pattern that may distract during suturing (regular-motion patterns allow the development of coping strategies such as the "wait and see" strategy that are less effective when motion is unpredictable5). It therefore may be helpful to slow the heart rate pharmacologically and temporarily pace the patient in a VVI mode. If AF is paroxysmal, epicardial ablation for pulmonary vein isolation on the beating heart may be applied before bypass grafting.

Results

The number of OPCABs performed has reached 30% of all coronary revascularizations worldwide, in some countries especially with limited medical and financial resources exceeding today 80%. In some units, OPCAB is used almost exclusively with no patient selection.

When discussing outcomes, it is important to keep in mind that despite the fact that propensity scoring was applied for most analyses, some selection bias cannot be excluded. As pointed out by Sergeant and colleagues and also Puskas and coworkers, clinically relevant reductions of mortality, stroke, and renal failure with the OPCAB approach mandate large cohorts of patients to reach statistical significance in the presence of above-standard on-pump performance.16,17

When the first reports on OPCAB were published, concerns were raised regarding (1) incomplete revascularization18–21 and (2) impaired graft patency owing to a more challenging technique.22 These fears are fueled by some larger prospective studies. Khan and colleagues found a reduced graft patency in OPCAB patients after 3 months with no difference in all other outcome parameters.22 In the ROOBY trial including more than a thousand patients in each group, the one-year outcome regarding cardiac death was inferior in the OPCAB group as well as the graft patency rate exept for the LIMA-LAD graft.23 Other studies like the SMART and Prague IV study that provide angiographic data on graft patency reveal equal patency rates for on- and off-pump bypass surgery.24–26

Regarding operative and short-term mortality, most studies are in favor of OPCAB. In a retrospective analysis of the Society of Thoracic Surgeons database for the years 1999 and 2000, including 17,969 OPCAB patients (8.8% of total), a significant survival advantage with OPCAB compared with on-pump CABG was demonstrated by risk-adjusted multivariate logistic regression analysis (OR 0.76, 95% CI 0.68 to 0.84) and conditional logistic regression of propensity-matched groups (OR 0.83, 95% CI 0.73 to 0.96).27 Similar results have been reported from another multicenter analysis consisting of some 7283 patients by Mack and colleagues. Following propensity score matching and multivariate regression analysis, the use of CPB was identified as an independent predictor of mortality (OR 2.08, 95% CI 1.52 to 2.83, p < .001).28 Especially in high-risk populations (eg, the elderly, those with EFs below 30%, and obese patients), OPCAB seems to offer a survival benefit.17,29–31 There are only sparse data on the midterm outcome. After 2 and 4 years, similar survival has been reported.18,32

There is growing evidence that neurocognitive outcome is better and stroke rate is reduced after OPCAB.33–35 According to a number of studies, CPB is an independent predictor of adverse neurologic outcome.36 The embolic burden measured by transit-time Doppler of the medial cerebral artery is reduced significantly during OPCAB.37–39 The risk of acute renal failure is decreased in off-pump surgery,40–42 especially in high-risk groups with preoperative renal insufficiency.43,44

The incidence of postoperative atrial fibrillation is reduced after OPCAB,44,45 and biochemical markers for myocardial injury (eg, creatinine kinase and troponin) are reduced after OPCAB.46–48 Blood loss is less, and transfusion rate is reduced.17 Overall, OPCAB reduces hospital costs by 15 to 35%31,49 possibly owing to decrease in length of stay and resource utilization.31

In a thorough meta-analysis, the International Society for Minimally Invasive Cardiac Surgery Consensus Group published the evidence for OPCAB.17 Accordingly, OPCAB reduces mortality and length of stay and the incidence of postoperative myocardial infarction (MI), renal failure, AF, and transfusion rate in mixed-risk and high-risk patients (Fig. 25-2).

In conclusion, OPCAB is a highly demanding procedure with a prolonged learning curve compared with conventional byass graft surgery. Some surgeons perform OPCAB almost exclusively, whereas others never use it at all. Comparisons are therefore difficult and maybe OPCAB is not the best option for every patient or for all cardiac surgeons. It is, however, an important option and must be mastered with the same technical precision as conventional CABG.50

One goal of minimally invasive cardiac surgery has been to avoid sternotomy to reduce the amount of surgical trauma and avoid wound complications. Therefore, coronary artery bypass techniques on the beating heart without sternotomy were developed. The operation was termed minimally invasive direct coronary artery bypass (MIDCAB), and since its introduction in the mid-1990s,51–55 it has found a widespread application. In some centers, MIDCAB is the preferred method of surgical revascularization for isolated coronary artery disease (CAD) of the LAD. In addition, MIDCAB is a valuable alternative to standard CABG or OPCAB in selected high-risk patients with multivessel disease and extensive comorbidity, who are at a prohibitively high risk for sternotomy.

Anesthesia

Standard monitoring is applied, and temperature management as for OPCAB is applied. Because single-lung ventilation is applied by using a double-lumen tube or bronchus blocker to provide selective right lung ventilation, short-acting anesthetics are used to allow for fast extubation.

Surgical Technique

Standard MIDCAB usually is performed through a left anterolateral minithoracotomy in a 10 to 20 degrees right lateral position. After making a 5- to 6-cm skin incision in the fifth intercostal space or the inframammary fold, the pectoralis muscle is displaced bluntly with minimal division following the muscle fiber orientation (muscle-sparing approach). This will decrease the likelihood of lung herniation that has been reported infrequently with this approach. The chest then usually is entered one intercostal space higher than the actual incision. Excessive rib spreading must be avoided at all times to prevent dislocation or fracture. Removal of a rib is almost never necessary. Take-down of the LITA usually is performed under direct vision, but endoscopic ITA takedown using a harmonic scalpel or telemanipulation systems has also been reported.55–57

The intrathoracic fascia is divided to facilitate take-down of the LITA, which usually is done in a pedicled manner. Takedown is performed from the fifth intercostal space to the origin of the subclavian artery. Using a sceletonized technique offers the advantage of gaining more graft length, but is, of course, more time consuming. Additional length can also be gained by dividing the mammary vein at its junction with the subclavian vein. Side branches are clipped or cauterized based on the preference of the surgeon. Heparin is administered prior to distal transsection of the graft. As in sternotomy OPCAB the ACT is kept at a level above 300 seconds. The pericardium should be opened above the course of the LAD and extended to the groove between the aorta and the pulmonary artery. This will facilitate location of the target vessel if excess epicardial fat or an intramuscular course is present. After that the target vessel is identified. To enhance exposure, one or two pericardial stay sutures may be used to position the heart. It is of utmost importance to have the region of anastomosis in direct and comfortable view. Standard reusable pressure stabilizers are then used to immobilize the target region (Fig. 25-3). Vacuum stabilizers in general are too bulky and not required for a single anastomosis to the LAD. Proximal LAD occlusion is performed using a 4-0 felt-pledgeted suture or vessel loops. Ischemic preconditioning is not helpful, but some surgeons use it to feel more comfortable when knowing that ischemia is well tolterated. The use of shunts is rarely necessary, but they may be applied based on the preference of the surgeon and indicated when strong coronary backflow is evident. Distal occlusion should be avoided whenever possible (99% of patients). A blower-mister is used in all cases to achieve a bloodless field. The anastomosis then is performed in a standard fashion using a 7-0 or 8-0 polypropylene running suture. Finally the LITA can be fixed on the pericardial tissue. Graft patency assessment is performed routinely using transit-time Doppler. A single chest tube is inserted into the left pleural space, and intercostal nerve blockade is applied using local anesthetics. Before closing the chest with one or two strong rib sutures the single lung ventilation is stopped and the left lung is inflated under direct view to control tension free course of the LITA. This is facilitated by keeping the LITA aside to the mediastinum using the suction tip or long forceps. Extubation usually is performed on the table for a few hours postoperatively. Patients are routinely started on antiplatelet therapy on the day of operation.

Results

A number of papers have reported excellent results with this approach. Immediate angiographic patency rates are in the range of 94 to 98% and thus similar to those reported for conventional CABG.54,58 At 6 months, patency rates of 94% have been reported.59 Reported in-hospital mortality for MIDCAB is less than 1% and compares favorably with the off-pump single-bypass mortality of 1.4% and with the mortality of single bypass with CPB of 3.6% that was been reported in the registry of the German Society for Thoracic and Cardiovascular Surgery.60 and is also lower than the 2.4% mortality that is reported from the STS database.61 The rates of perioperative major complications such as myocardial infarction and the need for target-vessel reintervention are low and comparable with standard CABG. However, because of an aortic surgery perioperative stroke is rare and the rate considerably lower compared with conventional techniques.

In our own series of 1918 patients who underwent MIDCAB from 1996 to 2009, in-hospital mortality was 0.8% (predicted mortality by Euroscore 3.8%), and stroke rate was 0.3%. Conversion to sternotomy was necessary in 1.6%. A total of 745 patients received routine postoperative angiogram demonstrating a 96.3% early patency rate. At 6-month follow-up, graft patency was 95.2% (n = 423). Five-year survival is 91.5% (95% CI 89.51 to 93.5%). (Fig. 25-4A) The freedom from MACCE and angina after 5 and 7 years was 88.6% (95% CI 86.4 to 90.9%) (see Fig. 25-4B). These results are in accordance with the findings of other groups.59,62,63

A few randomized trials comparing MIDCAB versus bare metal stenting in isolated proximal LAD lesions have demonstrated better early patency and superior freedom from target-vessel reintervention and angina for the MIDCAB group up to 5 years of follow-up.64–69

Some studies have pointed out that the lateral approach is associated with higher pain levels than sternotomy, mainly owing to the excessive rib spreading required for visualizing the LITA during takedown.55 Rib dislocation or fracture has been reported infrequently with this approach. Direct harvesting of the LITA is regarded as technically challenging and has been one of the arguments for many surgeons to disregard MIDCAB as the primary operation for patients who require surgical revascularization of the LAD. Limited working space and incomplete vision are blamed for insufficient graft length, incomplete mobilization, and the occasional reports of LITA injury or injury of the subclavian vein.

MIDCAB is a highly demanding technical procedure that should be started by surgeons who have sufficient experience in conventional and off-pump surgery. It has been shown that the complication rate of MIDCAB (namely conversion to sternotomy, reexploration for bleeding, and reintervention on the target vessel) is significantly lowered after an experience of 100 to 150 MIDCAB procedures.70 Therefore, it can be recommended to concentrate this operation on dedicated and experienced surgeons.

Even with improved outcomes of interventional procedures and less in-stent restenosis with the use of drug-eluting stents,71 MIDCAB, based on its very good long-term results,72 will remain an alternative revascularization strategy to PCI for patients with single-vessel disease, especially for complex ostial lesions, chronic occlusions, and in-stent restenosis.

The possibly least invasive approach for surgical revascularization is total endoscopic coronary artery bypass grafting (TECAB) on the beating heart. Working through ports has long been known for limiting the available space to perform motions, for substantially decreasing the dexterity of the operator, and for altering the hand-eye coordination.73 Active assistance, an indispensable component of open surgery, is difficult in thoracoscopic procedures. The transition from limited-access cardiac surgery to endoscopic cardiac surgery therefore complicates the procedure substantially and has rendered previous attempts at endoscopic CABG using conventional endoscopic instruments impossible. To overcome some of the instrument-related limitations, computer-enhanced instrumentation systems have been developed.

Principles of Telemanipulator-Assisted Cardiac Surgery

With the usage of telemanipulation devices the operator involved in the interaction is physically removed but not necessarily remote from the operation table. He instead operates at an input manipulator (surgical console, master console) from which he steers the executing manipulator (slave console) which is situated at the patient site. The slave console consists of all nessesary electromechanical equipment to operate two or three exchangable endoscopic instruments plus a high definition 3D endoscopic camera. Both haptic and visual information is fed back to the master console. This way a virtual 3D operative field is created wherein the surgeon can manipulate steering handles with a perfect hand-eye alignment. The introduction of telemanipulation technology to endoscopic surgery was able to address the key performance limitations of conventional endoscopic surgery, namely, reduced articulation, monocular vision, and loss of hand-eye coordination.

Surgical Technique

Standard monitoring for cardiac surgery is applied. Defibrillator pads are placed on the back and to the right side of the chest. Single-lung ventilation of the right lung is applied using a double-lumen endotracheal tube or a bronchus blocker. Temperature management follows the principles of OPCAB surgery. After draping the instrument arms and camera arm, camera and scope calibration are performed and the endostabilizer is prepared. A holding arm for the endostabilizer is mounted to the operating table rail on the patient's right side, and the operating table is rotated 10 to 15 degrees to raise the patient's left side.

After single right-lung ventilation is initiated, the camera port is placed in the fifth intercostal space 2 cm medial to the anterior axillary line. CO2 insufflation is begun for adequate visualization and to create working space as tolerated hemodynamically (usually 10 to 12 mm Hg of insufflation pressure). A 30-degree scope angled up is used for takedown of the LITA. The right instrument port is placed in the third intercostal space medial to the anterior axillary line, and the left instrument port is placed in the seventh intercostal space medial to the anterior axillary line. The instrument arms are centered for optimal range of motion by adjusting the respective setup joints, and the instruments are inserted. LITA takedown starts by dividing the intrathoracic fascia covering the LITA with low-power monopolar cautery. The LITA is dissected bluntly off the chest wall moving from the lateral to the medial aspect as a pedicle, keeping the lateral veins. Side branches are cauterized or clipped. Dissection is performed from the first intercostal space to the level of the bifurcation. The pedicle is not detached from the chest wall until the anastomosis is finally performed to avoid torsion of the graft. The distal end of the graft is skeletonized to facilitate suturing of the anastomosis. Epicardial fat is removed, and the mediastinal and diaphragmatic attachments to the pericardium are dissected bluntly to widen the available space. The pericardiotomy is performed with a longitudinal incision in the pericardium over the suspected course of the LAD. The ideal site for the anastomosis is determined by the absence of visible atheromatous plaques and avoiding proximity to bifurcations. At this point, changing the angle of the endoscope from looking upward to looking downward may enhance visualization. After heparinization (an ACT of 300 seconds is recommended), a vascular clamp is placed approximately 2 cm proximal to the transsection site. The LITA is clipped distally, cut, and spatulated in preparation for the anastomosis in situ. Graft patency is confirmed by briefly releasing the vascular clamp. The LITA pedicle is still left attached to the chest wall in order to keep orientation of the graft until the anastomosis is performed. A 12-mm subxyphoid cannula is inserted under endoscopic vision. Before introduction of the endostabilizer, temporary silastic occlusion tapes and a 7-cm 7-0 double-armed Prolene suture are introduced through this port and stored in the mediastinum. Some surgeons prefer Gore-Tex sutures to avoid the memory effect. Alternatively, nitinol clips (U-clips) may be used. The endostabilizer then is introduced under endoscopic vision by the patient-side surgeon (Fig. 25-5). Vacuum lines and irrigating saline line are connected, and the multilink irrigator is advanced into the field of view. The console surgeon then positions the stabilizer feet parallel to the LAD target site. After suction is applied, the feet are locked into position. After blunt dissection of the anastomotic target site, the silastic tapes are placed proximal and distal to the anastomotic site, and temporary occlusion is applied. After a 5- to 6-mm arteriotomy is performed, transsection of the LITA is completed, and the graft is brought in close proximity of the target site. The anastomosis is best performed by beginning at the middle of the medial wall (12 o'clock position), suturing inside-out on the LITA and outside-in on the LAD toward and around the heel. Care has to be taken to tension the suture continuously. After the needles are broken off, an instrument knot is tied. The occlusion tapes and vascular clamp are released and evacuated through an instrument port. The pedicle may be fixed to the epicardium by stay sutures. For graft patency, control transient time Doppler flow measurements can be performed endoscopically if a probe without a handle is available. This probe can be advanced through the stabilizer port. Alternatively, intraoperative angiography has been performed using a mobile angiography unit or modern C-arm systems when TECAB operation is performed in a hybrid suite. After the pleural space is drained under vision, the stabilizer and instruments are withdrawn, and the left lung is ventilated. A chest tube is inserted through one of the port holes. In case a four-arm system is used, the fourth arm is introduced after harvesting of the LITA in the third intercostal space in the anterior axillary line. It may be used to provide countertraction during epicardial fat removal and pericardiotomy and to present the pedicle during the anastomosis. The new version of the da Vinci system also will allow the use of a remotely controlled stabilizer that is placed on the fourth arm and thus can be adjusted from the console.

Results

Initially, TECAB was performed on the arrested heart using the Port-Access platform with femorofemoral cardiopulmonary bypass, endoaortic balloon clamping, and cardioplegic arrest. CPB time and cross-clamp times were in the range of 80 to 120 and 40 to 60 minutes, respectively. The reported patency rate for the TECAB procedure on the arrested heart ranged from 95 to 100% prior to discharge and 96% at 3-month follow-up angiography.74–77 A large single center study including 100 patients reported, besides good overall results and patency rates, anastomotic times of 10 to 30 minutes after a longer learning curve. Even more pronounced than in MIDCAB procedures (see previous) they also acknowledged that the learning curve continues beyond 100 operations.78

Endoscopic CABG on the beating heart is even more challenging.74,79,80 Based on an intention to treat basis, the conversion rate (elective conversion to a MIDCAB procedure) in a five-center registry was 33% (37 of 117). Conversions were mostly because of calcified target vessels or the inability to locate or dissect the LAD and rarely because of other conditions such as arrhythmia or hemodynamic instability. The patency rates for completed beating-heart TECAB procedures are in the range of 92 to 94%.61

TECAB can be performed safely but is currently restricted to few indications (eg, single-vessel bypass grafting of the LAD and occasionally double-vessel grafting), but it has the potential for endoscopic multivessel procedures.81,82 A more commonly applied technique is an endoscopic harvesting of both internal mammary arteries and direct coronary anastomosis via a mini-thoracotomy. This yields excellent results and very short recovery times for the patients.82,83

Despite the use of advanced telemanipulator technology, the TECAB procedure remains technically demanding and is performed infrequently worldwide. Long operation times, extensive use of material and operation room capacity combined with a stretched learning curve and well established minimally invasive alternatives have confined TECAB to few centers and single dedicated surgeons.

Talking about minimally invasive surgical revascularization almost always means revascularization of the anterior wall with the left internal mammary artery. The classical MIDCAB operation is only rarely extended to bypass a diagonal or even intermediate branch as well, typically with a Y-graft using a vein or radial artery.

Recent reports have proved the feasibility of complete revascularization for mutivessel disease. Through minimal incisions under direct vision or endoscopically with the help of a telemanipulator, harvesting of both mammary arteries is possible.84 For proximal anastomoses the aorta can be mobilized and partially clamped or the mammary arteries serve as feeding grafts for a radial artery or saphenous vein.

Accessibility of all areas of the heart is made possible by special stabilizers and suction retractors that allow distal anastomoses even on the beating heart (Fig. 25-6). As an alterative, the Heartport system for endoaortic clamping and cardioplegia can be used.

These techniques have not yet found entry into the clinical routine. However, the published series of patients show excellent results often times superior to conventional CABG or OPCAB.84 It can be assumed that all these operations were performed by dedicated, experienced surgeons on selected patients. Only a more widespread application of these procedures and the treatment of a broader variety of patients together with randomized studies would bring light to their significance in the future.

The hybrid approach for patients with multivessel coronary artery disease seeks to combine the advantages of percutaneous coronary intervention (PCI) and minimally invasive CABG. The principle was first described by Angelini in 1996.85 The goal is to minimize the surgical trauma but still gain complete revascularization. The rationale is that the excellent long-term results of LIMA to LAD grafting72,86 cannot be transferred to other areas of revascularization. This is particularly true for the still widespread venous bypass grafting. Here PCI can potentially achieve similar long-term results, yet with a somewhat higher rate of reintervention. Although recent studies underline the superiority of complete surgical revascularization,87 the avoidance of sternotomy seems to be very appealing to both patients and treating cardiologists.

However, combining the benefits of two different procedures also means adding the different risk inherent to each type of procedure. The risk of a surgical procedure, including the risk of general anesthesia and artificial ventilation, is combined with an increased risk of inferior PCI long-term outcome that includes the necessity of reinterventions and the possibility of eventual surgical multiple bypass grafting. Therefore the indication for hybrid revascularization should be discussed and agreed on by the treating cardiologist, cardiac surgeon, and, most important, the patient himself.

Indication for the Hybrid Approach

Current recommendations for coronary artery revascularization do not include hybrid procedures. This is because of limited availability of outcome data and a lack of randomized trials. Thus, choosing a hybrid approach is usually based on an individual decision. In all cases the patients with multivessel disease including the proximal LAD need to be informed that the best evidence-based treatment is a sternotomy CABG procedure. However, the different reasons for choosing a hybrid approach can be summarized as follows:

• Multimorbid or high risk patients: This is probably the best accepted indication and includes patients with a high risk for sternotomy associated problems such as mediastinitis or with reduced life expectancy. Patients with malignancies, redo patients with a history of deep sternal wound infections, patients dependent on crutches or a wheel chair or patients with additional risk factors such as diabetes, severe obesety, COPD, end stage peripheral occlusive disease, porcelain aorta, and history of stroke with paraplegia might also benefit from the hybrid aproach.
• Rescue PCI of CX/RCA: Patients with acute coronary syndromes presenting a culprit lesion in the circumflex or right coronary artery and additional stenosis of the LAD may undergo primary emergency PCI of the culprit lesion by the referring cardiologist. A MIDCAB procedure is usually scheduled 4 to 6 weeks later. A control angiogram confirming the patency of the stent should be done prior to surgery. In the presence of in-stent restenosis the patient can be scheduled for a standard bypass procedure.
• Patient preference: Some well informed patients want to avoid sternotomy and opt for a hybrid approach. Patients need to be informed that they might require future reinterventions including repeat target vessel revascularization or bypass surgery. Because the choice of the hybrid revascularization in these patients is not for medical reasons it deserves informed collaboration of patient, interventional cardiologist, and cardiac surgeon.

Timing of the Procedures

The optimal timing and order of revascularization is still discussed controversly.88 All three possible scenarios have inherent benefits and drawbacks:

• PCI before CABG: Performing the percutaneous intervention first is usually associated with an increased bleeding risk for the subsequent surgery because of double antiplatelet therapy. This can be avoided in stable patients who received a bare metal stent by postponing the CABG procedure for more than 4 weeks. When the interval between the two procedures is even longer, a preoperative control angiogram is reasonable to exclude early in-stent restenosis.

• The PCI-first strategy is most commonly applied when a culprit lesion other than the LAD requires urgent therapy.89

• CABG before PCI: This is the most frequently applied order. The percutaneous intervention is done after the patient has recovered from surgery. After protection of the anterior wall, the percutaneous aproach to the other coronary vessels is safer, even for the left main.90 A welcome side effect is the angiographic contoll of the minimally invasive bypass procedure.
• Simultaneous revascularization: The growing number of novel operating suites that provide true integration of surgical and fluoroscopic capabilities allows for complete hybrid revascularization in one session without moving the patient. After performing a standard MIDCAB/TECAB procedure the bypass quality is verified and the percutanous intervention is undertaken with the patient still under general anesthesia. In the rare case of a failed PCI easy conversion to conventional bypass surgery is possible. Patient acceptance for this approach is high yet it requires good collaboration and syncronizing of the schedules of the cardiologist and the cardiac surgeon.

Results

Although the concept of hybrid revascularization has been applied for almost 15 years the series of published results is not long and the reports oftentimes only involve some 20 to 50 patients. Additionally, the patients represent a very heterogeneous group with a wide range of risk profiles. The various means of revascularization both surgically (MIDCAB or TECAB) and interventionally (different types of bare metal stents and drug eluting stents) and their possible combinations further impair the comparibility. Randomized studies are not available.

There is a general consent that hybrid integrated revascularization is feasible and safe.91–95 Friedrich and colleagues reviewed the published results of eighteen studies including 367 patients. At six months, the LIMA stenosis rate was 2% and in-stent restenosis was 12%.91 A larger single center series was recently published by our group.89 During the follow-up period (208 patient years) 8 patients died. Kaplan-Meier survival was 92.5% (95% CI 86.5% to 98.4%) at one year and 84.8% (95% CI 73.5% to 94.9%) at 5 years. Twenty-three patients had an angiogram for recurrent symptoms of angina. One patient showed an occluded LIMA bypass. Five patients showed significant in-stent restenosis with the need for reintervention. At one year freedom from MACCE and angina was 85.5% (95% CI 76.9% to 94.1%) and 75.5% (95% CI 62.7% to 87.3%), respectively. (Fig. 25-7)

To minimize the overall trauma and wound healing problems of a bypass procedure, conduit harvest should be performed through limited incisions or endoscopically. There is a body of evidence indicating that although the quality of the conduit is not impaired by an endoscopic harvest, wound infections and other complications of the harvesting procedure are decreased substantially. The cosmetic advantage is obvious.

Endoscopic Saphenous Vein Harvesting

Despite the fact that arterial grafting yields better long-term results than venous grafting, and despite increased use of the IMA and other arterial grafts, the greater saphenous vein is still used frequently for CABG. The standard longitudinal open harvesting technique of the greater saphenous vein is associated with a 2 to 25% rate of wound complications (eg, dehiscence, delayed healing, infection, cellulitis, sepsis, and occasionally, limb amputation), complicating ambulation of the patient, prolonging hospitalization, and causing an economic burden.96–99 In addition, open saphenous vein harvest is associated with postoperative pain, swelling, neuropathy, long-term pain, and scarring impairing patient satisfaction.

Various techniques for endoscopic vein harvest exist that require one or two 2-cm incisions. For a single-incision technique, the greater saphenous vein is identified through a 2-cm longitudinal incision at the crease of the knee posterior to the medial femoral condyle. A space anterior and posterior at the surface of the vein is dissected, and a subcutaneous retractor or dissection cannula is introduced. An endoscope is inserted into the subcutaneous tissue. Exposure can be enhanced by insufflating CO2. The vein is mobilized circumferentially, and side branches are either clipped, coagulated using bipolar endoscopic cautery scissors, or vaporized using a harmonic scalpel. Whenever bipolar cautery is applied, a distance of at least 2 mm between the scissors and the vein should be kept in order to avoid thermal graft damage. Proximal and distal control of the greater saphenous vein is accomplished with endoscopic application of a Prolene suture, clips, or ligation loops. With this technique, the entire length of the vein can be harvested from the saphenous-femoral junction to the medial malleolus through a single incision. The wound is closed in a standard fashion, and the leg is wrapped circumferentially with bandages. In experienced hands, the procedure takes between 15 and 30 minutes.100 As with all endoscopic techniques, a learning curve is associated with endoscopic vein harvesting, with training involving approximately 30 patients and a conversion rate ranging from 0 to 22%.

Results

The ISMICS Consensus Group reviewed the results of 1319 randomized and 8023 nonrandomized patients. In this meta-analysis, the risk of wound complications was reduced significantly by 69% with endoscopic vein harvesting compared with the open technique (OR 0.31, 95% CI 0.23 to 0.43; p < .0001).101 The need for surgical intervention for wound infection also was reduced significantly (OR 0.29, 95% CI 0.12 to 0.70; p = .007). With regard to the incidence of moderate to severe postoperative pain, a reduction of 74% was found with endoscopic vein harvesting compared with the open technique (OR 0.26, 95% CI 0.12 to 0.55; p < .0001), and this reduction was 90% at 4 to 6-weeks follow-up (OR 0.10, 95% CI 0.03 to 0.37; p < .0001). The incidence of mobility disturbance at discharge was reduced by 69% (OR 0.31, 95% CI 0.15 to 0.65; p = .002).

One recent study reported worse angiographic and clinical outcome in patients after endoscopic vein harvest.102 Most studies, however, found no difference for myocardial infarction, angina recurrence or reintervention, and death over the short and midterm.101,103 However, the number of trials looking at cardiac outcomes and providing angiographic data on patency rates are too limited to allow any meaningful conclusion. The few trials that looked at vascular integrity and vessel wall trauma did not find a difference for the endoscopic versus open technique.104,105

Endoscopic Radial Artery Harvest

Use of the radial artery for CABG has regained popularity over the last decade. In conventional radial artery harvest, the incision runs from below the antecubital fossa to the wrist, along the medial border of the brachioradialis muscle. Although wound complications are reported infrequently, delayed healing of the forearm can cause severe discomfort.106 Objective sensory loss in 10% of patients and forearm scar discomfort in 33% undergoing open radial artery harvest have been reported.107,108 Endoscopic techniques for graft harvest have been developed subsequently.109

Surgical Technique

Collateral circulation from the ulnar artery to the palmar arch has to be verified pre- or intraoperatively using either the standard Allen test or modification of the test by applying Doppler or measuring oxygen saturation in patients in whom the signs of visual reperfusion are in doubt. In order to prevent brachial plexus injury, the arm should not be overextended above 90 degrees. One centimeter superior to the radial styloid prominence, a 2- to 3-cm incision is made, and the radial artery is identified and dissected. A subcutaneous retractor and a 5-mm, 30-degree endoscope are placed into the incision. By bluntly advancing the retractor through the subcutaneous tissue, the radial artery is visualized. Side branches and surrounding tissue are divided using an ultrasonic harmonic or thermowelding scalpel that is placed underneath the retractor. The fascia between the brachioradialis and flexor carpi radialis muscles is divided anterior to the radial artery with the scalpel to increase the space for insertion of the subcutaneous retractor.110 After division of all side branches, a vessel retractor is advanced from the distal incision to verify complete isolation of the conduit. The proximal radial artery is occluded using an Endoloop or clipped distal to the origin of the ulnar artery branch and transsected with endoscopic scissors. The graft is recovered through the distal incision, and the distal end is ligated. The incision is closed in a standard fashion.

Results

The reported incidences of neurologic complications after standard open harvesting technique of the radial artery vary in the literature from 2.4 to 30% and can be related to injury of the superficial radial nerve or the lateral antebrachial cutaneous nerve. With endoscopic technique, the latter usually is not encountered, because the dissection is performed underneath the brachioradialis muscle. Superficial radial nerve injury, however, still may occur during distal dissection.110 With regard to wound infections, endoscopic radial artery harvest is associated with a lower rate of infection (0 to 2.7%) compared with the open technique.100,111

Graft patency, clinical outcome, histological integrity, and in- vitro vasoreactivity are equal to open graft harvest.112–114 Thus, endoscopic radial artery harvesting can be recommended for better patient satisfaction and fewer wound healing complications.115

In summary, minimally invasive bypass surgery continues to play an increasing role in surgical revascularization. There is growing evidence in favor of OPCAB, which is already the preferred method of bypass grafting in many centers. MIDCAB is still limited to patients with single-vessel disease, and excellent long-term data confirm the efficacy of this approach. Endoscopic bypass grafting using robotic assistance is still an evolving procedure that is applied only to selected patients, and its continued application will strongly depend on technological improvements. As for endoscopic vein graft harvesting, there is a body of evidence suggesting superior results compared with an open harvesting technique, which also may be true for the technique of endoscopic radial artery harvest in the future.