Compared with adults who underwent off-pump coronary-artery bypass grafting surgery, those who underwent on-pump CABG had significantly lower rates of mortality and major adverse cardiovascular events at 5 years, results from a large randomized trial demonstrated.
“Given the results, it appears that innovative surgical approaches – such as the more technically demanding off-pump procedure – may not always provide superior clinical outcomes,” researchers led by A. Laurie Shroyer, PhD, wrote (N Engl J Med. 2017 Aug 17;377:623-32). “Additional long-term follow-up, evaluating these same outcomes rigorously at 10 years after CABG, appears to be warranted. Future research may identify the risk factors of the patients and the cardiac surgical processes of care that affect longer-term outcomes of coronary revascularization procedures, with the goal of increasing the rate of long-term event-free survival.”
Dr. Shroyer, of the Northport (N.Y.) VA Medical Center, and her associates conduced a 5-year follow-up study of patients who had participated in the original Randomized On/Off Bypass (ROOBY) trial, which compared the effectiveness of the two surgical approaches (N Engl J Med 2009 Nov 5;361:1827-37). During February 2002–June 2007, 2,203 patients at 18 medical centers were randomly assigned to either on-pump or off-pump CABG, with 1-year assessments completed by May 2008. The primary outcomes were the rates mortality and major adverse cardiovascular events at 5 years, while the secondary 5-year outcomes included death from cardiac causes, repeat revascularization, and nonfatal myocardial infarction.
The mean age of patients was 63 years, nearly all were male, 46% were between the ages of 55 and 64, and about 21% had chronic obstructive pulmonary disease. The researchers found that at 5 years, the rate of death was 15.2% in the off-pump group, compared with 11.9% in the on-pump group, which translated into a relative risk of 1.28 (P = .02). In addition, the rate of major cardiovascular events at 5 years was 31% in the off-pump group, compared with 27.1% in the on-pump group, which translated into a relative risk of 1.14 (P = .046). None of the secondary outcomes at 5 years met the prespecified threshold of a P value of .01 or less for statistical significance, when the off-pump and on-pump groups were compared. This included the rates of nonfatal myocardial infarction (12.1% vs. 9.6%, respectively; P = .05); death from cardiac causes (6.3% vs. 5.3%; P = .29); repeat vascularization (13.1% vs. 11.9%; P = .39), and repeat CABG (1.4% vs. 0.5%; P = .02).
“In combination with findings from other randomized trials and a 2012 Cochrane systematic review [Cochrane Database Syst Rev. 2012;14:CD007224], the 5-year outcomes in our study support the conclusion that off-pump CABG does not offer any substantial advantages over on-pump CABG except possibly in unusual situations such as, for example, in patients with an extensively calcified (porcelain) aorta, in whom the off-pump technique may result in less manipulation of the aorta, potentially decreasing the risk of aortic emboli or stroke,” the researchers wrote. “In light of the low rates of use of off-pump CABG in the United States, the findings in our trial may provide more of a real-world experience than those in the CORONARY and GOPCABE trials, which required surgeons with a very high volume of experience with off-pump procedures, as compared with the ROOBY trial and with most other surgeons who are based in the United States.”
They acknowledged certain limitations of the study, including the fact that the study population comprised mostly males who had multiple coexisting conditions, “so the findings may not be applicable to female patients or to patients who are not veterans.”
The study was supported by a grant from the Department of Veterans Affairs. Dr. Shroyer reported having received grants from the VA Cooperative Studies Program during the conduct of the study. Her coauthors reported having no financial disclosures.