Society of Cardiovascular Anesthesiologists

A Randomized Comparison of Off-Pump and On-Pump Multivessel Coronary-Artery Bypass Surgery

Khan NE, De Souza A, Mister R, Flather M, Clague J, Davies S, Collins P, Wang D, Sigwart U, Pepper J. N Engl J Med 2004; 350:21-8

Reviewer: Hong Liu, MD
University of California, Davis
Davis, CA

Objective:

The effect of the use of coronary-artery bypass surgery without cardiopulmonary bypass and cardiac arrest ("off pump") on graft patency remains uncertain. To address this question, a prospective, randomized, controlled study to compare graft-patency rates and clinical outcomes in off-pump surgery with conventional, "on-pump" surgery was conducted.

Methods:

In this study, 50 patients were randomized to undergo on-pump coronary-artery bypass grafting and 54 to undergo off-pump surgery. Surgical and anesthetic techniques were standardized for both groups. Clinical outcomes and troponin T levels were measured. Three months later, the patients underwent coronary angiography, including quantitative analysis to assess graft patency.

Results:

The mean age of the patients was 63 years, and 87 percent were men. The on-pump group received a mean of 3.4 grafts, and the off-pump group 3.1 (P=0.41). There were no deaths. There was no significant difference in the median postoperative length of stay between the two groups (seven days in each group). The area under the curve of troponin T levels was greater during the first 72 hours in the on-pump group compared to the off-pump group (30.96 hr x microg per liter vs. 19.33 hr x mcg per liter, P=0.02). At three months, 127 of 130 grafts were patent in the on-pump group (98 percent), as compared with 114 of 130 in the off-pump group (88 percent, P=0.002). The patency rate was greater for all graft territories in the on-pump group compared to the off-pump group.

Conclusion:

In this randomized study, off-pump coronary surgery was as safe as on-pump surgery and caused less myocardial damage. However, the graft-patency rate was lower at three months in the off-pump group compared to the on-pump group, and this difference may have implications with respect to long-term outcomes.

Comments:

Coronary-artery bypass grafting (CABG) performed with cardiopulmonary bypass and cardiac arrest ("on pump") provides a motionless, bloodless surgical field, allowing optimal conditions for the construction of coronary anastomoses and has become a well-established treatment modality for patients with coronary artery disease (1). However, the systematic inflammatory reaction initiated by the cardiopulmonary bypass (CPB) circuit results in mechanical trauma to blood cells, activation of immunological cascades, impaired hemostasis, and impaired neurological, renal, and gastrointestinal functions (2, 3). Following the first large series reported in 1991(4) and the development of new cardiac stabilization devices, the technique of the off-pump CABG has proliferated although it has not been universally adopted by all surgeons or all cardiac surgical centers. Only 8.8 percent of all coronary-artery bypass operations performed in the United States between January 1999 and January 2001 were performed off pump. Reported results of off-pump CABG in comparison to on-pump CABG reamin controverial especially in regards to graft patency. The authorss evauated graft patency and quality of grafts in a randomized study comparing on-pump with off-pump surgery.

The authors found that the patency rate for grafts performed off pump was lower at three months than that for grafts performed on pump (overall patency, 88 percent vs. 98 percent). The territory of the left anterior descending artery, often described as the easiest territory to graft off pump, also had a lower rate of patency in the off-pump group. Radial-artery grafts appear to be the most vulnerable conduit in the off-pump group. Although this study consisted of a limited number of cases, and may not reflect the experience of all surgeons or centers that perform this operation, the results provide us with valuable information, and further larger clinical trials with longer follow-up may be needed.

References:

Ghali WA, Quan H, Shrive FM, et al. Outcomes after coronary artery bypass surgery in Canada: 1992/93 to 2000/01. Can J Cardiol. 2003;19:774-781
Westaby S. Organ dysfunction after cardiopulmonary bypass: a systematic inflammatory reaction initiated by the extracorporal circuit. Intensive Care Med. 1987; 13: 89-95
Butler J, Rocker GM, Westaby S. Inflammatory response to cardiopulmonary bypass. Ann Thorac Surg. 1993; 55: 552-559
Benetti FJ, Naselli G, Wood M, Geffner L. Direct myocardial revascularization without extracorporeal circulation: experience in 700 patients. Chest 1991;100:312-316.

Table of Contents: