On-pump and off-pump bypass surgery: tools for revascularization.

Abstract

Cardiopulmonary bypass (CPB) has been fundamental to the development of coronary bypass surgery. Although some early coronary operations were performed without CPB, widespread coronary surgery only occurred with the aid of perfusion, a support system that has allowed complex coronary reconstruction to be carried out with effective myocardial protection, end organ protection, and consistent and relative safety. See p 887 But CPB is not normal. Despite advances in perfusion technology, negative effects of CPB include blood trauma, activation of a series of inflammatory responses, nonpulsatile flow, and possible embolization of air or debris—most particularly embolization of atherosclerotic debris from the aorta. Within the last decade, increasing attention has been directed to the concept of decreasing perioperative risk by avoiding CPB: “off-pump” or “beating heart” bypass surgery. As a result of increased surgical experience and the development of enabling technology, such as stabilization and exposure devices, off-pump surgery has become increasingly feasible, and today, 20% to 25% of coronary operations in the United States are carried out without CPB. We now know that off-pump bypass surgery can be accomplished, but does it decrease risk, what risks are decreased, and for whom? As the off-pump concept moved into the surgical arena, the hope was that it would decrease perioperative morbidity and possibly mortality, and the fear was that revascularization would be more difficult, less complete, and less effective over the long term. Multiple studies have addressed these issues, including observational studies of large patient populations using statistical risk adjustment, observational trials of smaller patient subsets thought to specifically benefit from off-pump surgery, and randomized trials. All of these study designs suffer from some disadvantages. Nonrandomized studies have the disadvantages of bias in treatment selection and the possibility that differences in patient-related characteristics will mask the effect of surgical strategy, and randomized trials …