No major differences in 30-day outcomes in high-risk patients randomized to off-pump versus on-pump coronary bypass surgery: The Best Bypass Surgery Trial
Møller CH, Perko MJ, Lund JT, Andersen LW, Kelbaek H, Madsen JK, Winkel P, Gluud C, Steinbrüchel DA.
Circulation 2010 Feb 2;121(4):498-504.
Reviewer: Mohammed Minhaj, MD
University of Chicago Medical Center, Chicago, IL
In low-risk patients, off-pump coronary artery bypass graft (CABG) surgery appears to be safe when compared to CABG with the use of cardiopulmonary bypass (CPB or “on-pump”). Observational studies in high risk patients even suggest that off-pump surgery may be even more beneficial in high-risk patients. The authors’ goal was to test this hypothesis in a randomized, controlled, trial in high-risk patients. The study randomly assigned 341 patients with EuroSCORE ≥ 5 and 3-vessel disease to have CABG surgery either on- or off-pump. The primary outcome was a composite of adverse cardiac and cerebrovascular events, including mortality, myocardial infarction, stroke, low cardiac output, re-operations, shock, etc. The two groups were similar at baseline and the mean number of grafts per patient did not differ significantly between the two groups. Fewer grafts were performed to the lateral part of the left ventricle territory during off-pump surgery vs. on-pump surgery. There were no significant differences in the primary composite outcomes or the individual outcomes at 30 days. The authors concluded that both on- and off-pump CABG surgery could be performed on high-risk patients with low short-term complication risk.
The goal of this study was to examine whether there were any differences in patients who were deemed “high-risk” as most randomized trials comparing on- and off-pump CABG were comprised of “low-risk” subjects (e.g., younger patients with better ventricular function). There have been trials suggesting benefits to an off-pump approach in “high-risk” patients, but these have been observational and not randomized. These observational trials have suggested that off-pump CABG is associated with reduced perioperative morbidity and mortality.
However, this study demonstrated that at least in the short-term there is no difference between pursuing an off-pump or on-pump approach to CABG surgery. A concerning trend however, is the fact that while the numbers of grafts were not different between the two groups, patients in the off-pump CABG group had fewer grafts on the lateral aspect of their ventricles. Whether this has long-term sequelae needs to be answered especially since another cause for waning enthusiasm regarding the off-pump approach has been the concept of “incomplete revascularization”— meta analyses of off-pump data suggest that patients receive fewer grafts when an off-pump approach is undertaken. Future studies examining the consequences of fewer grafts overall or in the lateral wall of the ventricle need to be conducted.
There were several strengths to this paper, including the fact that no patients were lost to follow-up, that outcomes were assessed by blinded individuals to reduce bias and a high (~85%) rate of inclusion of eligible patients. However, this study also had some limitations. It was at a single-center with a small group of cardiac surgeons. The sample size was more limited than the study published by Shroyer et al, and the results may not be as generalizable given the single-center design. It also only followed short-term outcomes.
Debates over the potential benefits of off-pump CABG continue to persist in the literature and enthusiasm over the use of this approach has waned recently with reports of worse graft patency/outcomes and incomplete revascularization in patients who undergo off-pump CABG surgery. In 2009, Shroyer et al., published a large, randomized controlled trial that demonstrated worse 1 year composite outcomes and graft patency in the off-pump group as compared to the on-pump group of patients enrolled. Interestingly and similar to this paper, composite outcomes at 30 days were NOT significantly different. This suggests that patients enrolled in the above study should be followed for long-term outcomes to appreciate if off-pump CABG is more beneficial than on-pump CABG. The results of this paper do provide some more information with respect to the question of: “Will off-pump be better than on-pump for this patient?” but we still need more long-term data on both outcomes and graft patency if we hope to provide a better answer.