This will focus on the surgical technique that we feel provides the most effective and safe method of off-pump coronary revascularization.

Off-pump coronary artery bypass (OPCAB) has been practiced to some degree for many years, but it has regained popularity only recently with the development of devices that allow for superb exposure and stabilization of the anastomotic area. This technology continues to develop and improve over time. With the spectrum of patients presenting with coronary disease becoming more complex and higher risk, surgeons have been looking for surgical options that may reduce complications. OPCAB has this potential because it avoids cardiopulmonary bypass (CPB) and the associated morbidity.

OPCAB is not simply the standard coronary bypass operation performed without the assistance of CPB. Rather, it is a concept whose primary goal should be the reduction of morbidity and mortality. The technical result should be identical to that for a standard coronary artery bypass graft (CABG) operation: the same number, location, and quality of anastomoses. Further, OPCAB must be a reproducible technique, allowing it to be taught to other surgeons and incorporated into the training of cardiothoracic surgical residents. This aspect is something that has been studied in a scientific fashion at Gasthuisberg Hospital in Belgium. There are now objective data to support this technique, which can be safely taught to residents and can also be used to retrain established surgeons.¹ Ideally OPCAB should be applicable to the entire spectrum of patients. In Leuven, a practical algorithm is used to determine whether a particular patient has a bypass performed with or without CPB (Fig. 28-1). Obviously, for any patient in extremis, receiving cardiac compressions, or with malignant arrhythmias, emergent institution of CPB is lifesaving and necessary. In this patient subset, the authors perform CABG on CPB, but with a beating heart to minimize further ischemia. In more stable patients, the next branch in the decision tree involves whether the patient has had an acute infarct (within 3 days of surgery). Regardless of other risk factors or comorbidities (e.g., complexity of coronary lesions, cardiomegaly, redo surgery, ejection fraction), if the infarct is more than 3 days old, the procedure is performed off-pump. For an acute infarct, a pulmonary artery (PA) catheter is placed and the cardiac index (CI) is measured. If the CI is less than 1 L/min/m², the patient is placed on CPB and the revascularization is completed with the heart beating. For patients with a CI greater than 2 L/min/m², procedures are performed off-pump. In patients with a CI between 1 and 2 L/min/m², a determination is made as to the presence or absence of pulmonary edema. The authors believe that pulmonary vascular congestion is an indication of severe left ventricular dysfunction and indicates a patient who probably will not tolerate cardiac manipulation and may need assistance with oxygenation. These patients undergo CABG with CPB, but with the heart beating.

A less evident component of a successful OPCAB program is the ability to perform these procedures without undue stress on the operating team: surgeons, anesthesiologists, and nurses. Many teams feel averse to performing OPCAB because of the level of anxiety that results from conducting this technique under suboptimal conditions. Hemodynamic instability, ischemia, unpredictability, and perhaps an open confrontation between the anesthetic and surgical teams all contribute to this. The structured environment and organized, stepwise technique developed by one of the authors (Dr. Sergeant) has created an atmosphere of collegiality and open communication, eliminating these stressful triggers and leading to a pleasant operating environment.

This approach involves a number of factors geared toward minimizing risk and enhancing the safety of the procedure. The key to this is the optimization of intraoperative patient hemodynamics (i.e., heart rate/rhythm, blood pressure, cardiac filling pressures, electrolytes, and body temperature) before cardiac manipulation. This provides a stable platform that allows the surgeon to enucleate the heart from the pericardium safely during the anastomotic period. Further, it optimizes the myocardium to tolerate any transient ischemia that is produced. Without proper anesthetic conditioning, the entire concept of OPCAB can be unsafe and the operation should not be performed. Each step in the authors’ technique is designed to eliminate or reduce the risk associated with off-pump revascularization. Not all steps are essential for every coronary anastomosis in every patient. However, it is challenging to predict which circumstances will produce instability for any specific patient and/or anastomosis, and it is for this reason that the authors use the safeguards in every patient and for every anastomosis. Without such stringent controls, a certain percentage of patients will require urgent/emergent conversion to on-pump CABG, which clearly has been shown to result in significant morbidity and mortality.^1–3

Surgeons also must be able to perform anastomoses in smaller spaces and on vessels that may be at unfamiliar angles. To maintain hemodynamic stability, the heart must be manipulated so that mitral insufficiency is not created or worsened and the right heart may fill properly. In many cases this leads to the anastomoses being more technically challenging than what is encountered on-pump. It is important that the OPCAB surgeon retrain to become competent in creating high-quality anastomoses that are durable and achieve patency rates equivalent to those of anastomoses completed with CPB and an arrested heart. Methods to accomplish this are discussed later in this chapter.

The motivation for adopting the OPCAB approach to surgical coronary revascularization should focus upon reducing complications while preserving excellent long-term outcomes. In evaluating whether to use a new technique in one’s practice, it is important to identify the “drivers” that influence the decision. Inappropriate drivers probably will lead to failure of the reengineering process. Examples of inappropriate drivers include marketing, ambition, and excitement about a novel technique. In the authors’ early experience with OPCAB, we did not have the proper motivation and for that reason did not perform more than about 10 percent of CABGs off-pump. Further, these cases were very stressful and unpredictable in light of the authors’ desire to try out a new technique.

Coronary bypass surgery has achieved unparalleled long-term results that have been studied more extensively perhaps than the results of any other surgical procedure. Although surgeons have relied on this record to maintain patient referrals, the advent of drug-eluting intracoronary stents has produced excellent results as well. Percutaneous stenting, however, is associated with vastly reduced early morbidity and mortality. It was this realization that led the authors to the proper “driver” toward OCPAB surgery: the goal of eliminating early complications while maintaining the outstanding long-term results expected for CABG surgery. With this goal in mind, a technique was developed that minimizes risk for the patient at every possible step.

Economic Impact

It is important to discuss the impact of the OPCAB approach on the real costs of surgical coronary revascularization. There are two methods by which OPCAB may influence cost. The first is a “production line” effect that involves eliminating over 50 CPB-related instruments as well as the CPB circuit and reducing operating room personnel (e.g., no perfusionist, fewer surgeons/nurses). A second effect is realized in terms of reduced morbidity as a consequence of the new technique. This effect (e.g., reducing stroke or renal failure rates) may apply only to a very small number of patients but constitutes a huge cost benefit. Combined, these effects lead to dramatic overall cost reductions once a complete reengineering toward OPCAB has been realized.

Team Approach

A successful OPCAB program requires that all operating room staff (surgeons, anesthesiologists, and nurses) work together as a team with open lines of communication. This ensures that all members are able to anticipate each step and its potential complications so that they are prepared to correct any abnormalities. The authors also believe that it is essential for the surgeon and the anesthesiologist to engage in frequent collegial communication during the procedure so that both parties agree as each step in the operation is performed. This has the added benefit of producing a stress-free environment for all members of the operating team and leads to improved multidisciplinary care for the patient. If at any point and for any reason the anesthetist does not feel that the patient is stable enough to proceed, the manipulation is delayed until the hemodynamics have been optimized.

The authors’ OPCAB technique has evolved over time. Since 1999, new devices have become available and the authors’ experience with optimal anesthetic management and surgical manipulation has improved greatly. This goal of safe OPCAB and zero tolerance for conversion to CPB requires that every effort be made to ensure safety.

Patient Conditioning

The first step in a successful OPCAB procedure begins before the incision is made. It is critical that the patient’s hemodynamics be optimized to tolerate the stresses that surgical intervention will apply. To this end, patient hemodynamics must be “conditioned” adequately before any surgical manipulation of the heart. Thus, patients must have a normal heart rate [50–70 beats per minute (bpm)], normal systemic and pulmonary arterial pressures, normothermia, and normal electrolytes. For these reasons, monitoring in the authors’ institution includes radial arterial catheterization, central venous and Swan–Ganz catheterization, and transesophageal echocardiography (TEE) for all OPCAB cases. TEE permits the detection of new wall motion abnormalities that may indicate early myocardial ischemia. PA monitoring is used to follow diastolic pressures as an early indicator of cardiac ischemia; alternatives include direct left atrial or pulmonary arterial pressure monitoring. It is the role of the anesthesiologist to adjust the patient’s filling pressures to achieve pulmonary arterial diastolic (PAD) pressures between 10 and 15 mm Hg. In patients with certain preoperative conditions (e.g., atrial fibrillation, left ventricular hypertrophy), higher PADs are tolerated, reflecting the need for higher filling pressures. This is the exception, however, and the vast majority of patients will have the safest operation with PADs in the lower range. As will be described below, during most of the anastomotic period the heart lies outside the pericardium and the triangle of Einthoven, making detection of ischemia by electrocardiography (ECG) and TEE more difficult. Hence, the authors use the Swan–Ganz catheter as the primary mechanism to detect, treat, and follow this occurrence.

Another important role of the anesthesiologist is to optimize myocardial oxygen metabolism; this is achieved primarily by maintaining a normal heart rate. Patients are β-blocked adequately before surgery, with heart rates usually maintained around 60 bpm. However, if a patient has a heart rate greater than 80 bpm, intravenous metoprolol is given to ensure that the heart is well protected from catecholamine surges. Any patient whose heart rate is below 60 bpm has atrial pacing wires placed and is paced atrially throughout the procedure. Atrioventricular sequential pacing is used for patients with additional conduction abnormalities. Oxygen demand is optimized through the strict avoidance of any inotropic medications, maintenance of filling pressures by leg elevation without Trendelenburg and volume infusion, and nitrates and α₁-agonists as needed to optimize coronary perfusion pressure.

Serum electrolytes and acid–base balance also must be normalized to minimize triggers of arrhythmias. Serum potassium levels are checked hourly and repleted if they are less than 4.0 mEq/L as a protective measure against extrasystoles, atrial fibrillation, ventricular tachycardia, and ventricular fibrillation. In the authors’ concept, extrasystoles [premature ventricular contractions (PVCs)] are considered abnormal and should never occur. When a PVC does occur, its etiology must be determined. The surgeon may have caused the PVC by touching the heart, and if this is the case, the anesthesiologist is notified and the operation proceeds. However, if the PVC was spontaneous, the patient’s potassium level is checked. Levels below 4.0 mEq/L are repleted, but if they already are in the normal range, the abnormal beat is considered ischemic in origin until proved otherwise. The ECG–ST segments should be evaluated, as should the PA diastolic pressure and TEE for wall motion abnormalities. Only when all the members of the team are convinced that there is no ongoing ischemia does the operation continue. The authors have noticed, for instance, that a slightly misplaced stabilizer device may occlude coronary vessels, causing ischemia, which manifests as multiple PVCs. Only by adhering to these stringent principles can problems be identified and corrected in a timely fashion, avoiding hemodynamic compromise in the patient.

The patient’s body temperature is regulated by two means. First, the room is kept warm until the patient is prepped and draped. Subsequently, it may be lowered to a comfortable temperature for the surgical staff. Second, a heated water blanket is placed underneath the patient and maintained at 40°C throughout the procedure. With these techniques, it is rare for a patient to leave the operating theater with a core temperature below 36.3°C.

Incision

A median sternotomy is the incision of choice to perform OPCAB. This approach provides the most complete exposure for completion of all potential anastomoses while optimizing technical precision. Any coronary artery may be grafted with this exposure, and complex arterial reconstructions may be performed. Minimally invasive coronary artery bypass (MIDCAB) permits the use of a smaller minithoracotomy but is limited mainly to isolated revascularization of the anterior wall. More complex reconstructions are not possible. There also is concern that the quality of these anastomoses is reduced; this may translate into poorer long-term graft patency. For all these reasons, the authors strongly advocate a full median sternotomy for the optimal performance of OCPAB in all situations.

After the internal mammary artery (IMA) is mobilized from the chest wall, the pericardium is opened longitudinally, extending to the apex of the heart and completely along the diaphragm. The left pericardial edge is suspended from the retractor/drapes, but the right pericardial edge is left alone. This serves to rotate the heart slightly to the right, bringing the left anterior descending (LAD) artery closer to the midline of the operating field.

Conduit Harvest

It is the standard of care to use at least one IMA for coronary revascularization. Usually the left IMA is harvested, but there are certain circumstances in which either right or bilateral IMA grafting is indicated. Patients with a patent dialysis shunt in the left upper extremity are at risk for a steal syndrome if a left IMA conduit is used. Also, an IMA should not be harvested ipsilateral to a subclavian artery stenosis. Patients with extensive atherosclerosis may benefit from angiography of the IMAs and the subclavian arteries during cardiac catheterization. For younger patients who are not diabetic, many surgeons choose to use both IMAs to provide two pedicled arterial grafts; this technique has demonstrated long-term patency. The specific technique for taking the IMA off the chest wall is beyond the scope of this chapter. The authors routinely open the pleura during IMA harvest, but this is a matter of surgeon preference. The authors routinely leave the right pleura intact and do not place the heart into the right chest.

A reversed saphenous vein is the most common conduit for the remaining grafts. This conduit is easy to harvest, is usually in good supply, is easy to work with, and has well-documented long-term patency in most situations. Newer techniques of endoscopic harvesting have further popularized the use of the saphenous vein because this technique reduces lower extremity wound complications and discomfort dramatically. This has now become standard practice for most coronary revascularization procedures requiring saphenous vein harvest.

Alternative choices for a conduit are generally more difficult to harvest, are often more difficult to work with, and have lower long-term patency rates. These choices include the lesser saphenous vein, the cephalic/basilic vein, a radial artery, the gastroepiploic artery, and cryopreserved vein. Only in situations in which conduit availability is severely limited should these other choices be considered.

Anticoagulation

Anticoagulation consists of an intravenous heparin bolus administered at the completion of IMA harvesting to achieve a target activated clotting time (ACT) of 400 s or more; the heparin dose is usually 300 U/kg. ACT measurements are repeated every 20 min, and additional heparin is administered as necessary. Many authors routinely use a target ACT of 250 s despite a lack of evidence that this level is safe or prevents graft thrombosis. If the ACT level is too low to begin with or is not measured with adequate frequency, there is the potential for graft thrombosis. Furthermore, some data suggest that patients undergoing OPCAB have intrinsic hypercoagulable states (Fig. 28-2).³ The authors feel that full-dose heparin should be used in all circumstances during the anastomotic period to maximize graft patency. Because OPCAB patients do not develop coagulopathies related to CPB, the authors feel strongly that performing vascular anastomoses with only partial anticoagulation confers a significant risk of thrombotic complications. Full protamine reversal is instituted at the completion of all anastomoses.

Enucleation

In contrast to conventional CABG surgery, the left IMA to the LAD coronary artery is usually the first graft anastomosis performed in OPCAB procedures. This is the case because it is often the easiest to complete, requires minimal cardiac manipulation, and provides revascularization of the most critical myocardial region, conferring added protection from hemodynamic stability and arrhythmias during the remainder of the operation. The details of exposure for this anastomosis are described later in this chapter. After this step, the heart is enucleated from the pericardium so that the other coronaries may be visualized, stabilized, and grafted. This process is simple and consists of two parts.

First, a deep pericardial anchor stitch is placed with a long, heavy monofilament suture. The location of this stitch is of the utmost importance (Fig. 28-3). It should lie adjacent to the right inferior pulmonary vein, as far to the right as possible. This serves to lift the heart very effectively up out of the pericardium, bringing the atrioventricular groove closer to the surgeon. There has been much discussion in the literature regarding the use of various sling techniques^4,5 and we firmly believe this technique optimizes exposure with minimal risk if performed properly. Even more important, however, is the fact that this position prevents any distortion of the atrioventricular axis so that mitral insufficiency is not created or worsened if it is already present. A long sponge (opened up lengthwise) then is passed through the suture, and a tourniquet is advanced until the sponge is at the anchor stitch.