Long-term survival benefit seen in on-pump vs off-pump CABG

There is a small but significant long-term survival benefit of on-pump coronary artery bypass graft (CABG) surgery when compared to off-pump procedures, according to a meta-analysis published online Feb. 26 in the Journal of the American College of Cardiology.

Neil A. Smart, PhD, and colleagues looked at outcomes of six randomized clinical trials (RCTs) containing 8,145 participants. They only included studies with follow-up periods of at least four years.

Overall mortality was 12.3 percent in the on-pump group versus 13.9 percent in those who received “beating heart” procedures—a 16 percent relative risk reduction. There were insignificant differences in the odds of myocardial infarction, stroke, angina and the need for revascularization.

The researchers conducted the meta-analysis to incorporate the publication of two large RCTs that recently published five-year outcomes, and because most prior research comparing on- versus off-pump CABG evaluated short-term outcomes.

In five of the six RCTs they included, on-pump CABG had better long-term survival rates, although that difference only reached statistical significance in one of the trials. However, the pooled analysis did meet statistical significance—a pattern mirrored in retrospective studies.

“On the whole, these (retrospective) studies have shown no difference in mortality between off-pump and on-pump CABG,” the authors noted. “In the two exceptions, long-term survival rates were significantly better in the on-pump group. This bears some similarities to the current meta-analysis in which individual studies showed no differences in survival, but the overall mortality was statistically in favor of the on-pump group, although whether the absolute difference is of clinical significance may be more uncertain.”

The quality of the studies included in the meta-analysis was moderate, with them scoring between 2 and 4 on a scale of 6. Another limitation was the studies used different techniques for myocardial protection during on-pump CABG.

In a related editorial, two cardiovascular surgeons from New York City called for additional randomized trials to help determine which specific patients may benefit from each approach. Until that data is available, they said, it is more important they are operated on by a surgeon with a strong track record than whether they undergo CABG via one technique or the other.

David H. Adams, MD, and Joanna Chikwe, MD, also pointed out technological and clinical advances have made CABG operations safer—especially on-pump, which relies less on technical expertise.

“In 2018, CABG patients can and should expect to be on optimal medical therapy pre- and post-operatively, have effective perioperative blood conservation and glycemic control strategies in place, undergo intraoperative transesophageal echocardiography and epiaortic ultrasound to assess the ascending aorta, benefit from the evolution of cardiopulmonary bypass support that is almost unrecognizable from the technology of even 10 years ago, and receive care from multidisciplinary teams that bring a level of experienced sophistication and safety that was primarily available in only select centers until relatively recently,” wrote Adams, with Icahn School of Medicine at Mount Sinai; and Chikwe, with Stony Brook University.

The editorialists concluded the on-pump technique should remain the standard of care “given the equivalent short-term safety of both approaches and the superior long-term outcomes now reported.”