Technology insight: randomized trials of off-pump versus on-pump coronary artery bypass surgery

Coronary artery bypass grafting has proven a remarkably effective treatment for occlusive coronary artery disease, with demonstrable impact on both symptoms and survival. As conducted traditionally, cardiopulmonary bypass is required, and a global myocardial ischemic insult imposed with aortic occlusion under the protection of cardioplegic arrest. Despite the remarkable success of this approach, concerns over the systemic effects of bypass, including neurologic sequelae as well as ischemic myocardial injury, have stimulated development of techniques and technology to perform coronary bypass 'off-pump'. This technique obviates the need for the bypass machine and imposes only brief regional ischemia during construction of each individual anastomosis. Despite enthusiastic support by a devoted cohort of surgeons, and a host of nonrandomized retrospective studies demonstrating an apparent benefit to the off-pump technique, the technique has not been universally adopted. How can there be such controversy over what appears to be a superior approach? In part, many surgeons are concerned that the greater technical difficulty of the technique will impact long-term results adversely. There is also uncertainty with regard to the actual advantage of off-pump coronary artery bypass over the tried-and-true methods. Surgeons recognize that the results of any surgical series are particularly subject to the influence of subtle selection biases. Accordingly, prospective randomized studies add particular value to the debate. It is the aim of this review to examine the evidence for off-pump coronary artery bypass critically, from a surgeon's perspective, with particular emphasis on knowledge derived from a representative selection of published prospective randomized studies.