A variety of outcomes were poorer with off-pump than with on-pump coronary artery bypass graft in a prospective, randomized trial comparing the procedures.
Short-term and 1-year mortality, as well as rates of major complications, MI, revascularization procedures, and graft patency, were worse with the off-pump approach. Rates of neuropsychological sequelae were not significantly different.
“Our trial did not show any overall advantage to the use of the off-pump” coronary artery bypass graft (CABG), said A. Laurie Shroyer, Ph.D., of Northport (N.Y.) Veterans Affairs Medical Center, and associates in the Randomized On/Off Bypass (ROOBY) trial.
The study involved 2,203 patients undergoing elective or urgent CABG between 2002 and 2008 at 18 VA medical centers. Most (over 99%) were white men who were current or former smokers and had at least one comorbid condition; over 40% had diabetes. A majority had three-vessel coronary artery disease and normal left ventricular function, the authors wrote.
The patients were randomly assigned to on-pump (1,099 patients) or off-pump (1,104 patients) surgery while waiting in the preoperative holding area.
The primary short-term end point was a composite of death or major complications such as reoperation, new mechanical support, cardiac arrest, coma, stroke, or renal failure requiring dialysis within 30 days. The primary long-term end point was death from any cause, nonfatal MI, or repeat revascularization within 1 year.
The short-term composite outcome was not significantly different between the two groups, affecting 7.0% of the off-pump group and 5.6% of the on-pump group. In contrast, the long-term composite outcome was significantly higher in the off-pump group (9.9%) than in the on-pump group (7.4%).
A subsequent sensitivity analysis of the data “showed even stronger advantages for on-pump procedures,” the investigators said (N. Engl. J. Med. 2009;361:1827–37).
The rate of graft patency at 1 year was significantly lower for the off-pump group (82.6%) than the on-pump group (87.8%). Significantly more patients in the off-pump group (36.5%) had at least 1 occluded graft than in the on-pump group (28.7%).
Among those with no occluded grafts, the primary 1-year composite outcome was lower in the on-pump group than in the off-pump (3.3% vs. 6.4%), because “there was less complete revascularization in the off-pump group,” the researchers wrote.
A subset of 1,156 study subjects had completed a battery of neuropsychological tests at baseline and was retested at 1 year. Dysfunctions in attention, memory, and visuospatial skills were assessed.
Unexpectedly, there were no significant differences between the two treatment groups on these measures, and the changes in individual test scores either were minimal or showed improvement after surgery for both groups, Dr. Shroyer and colleagues said.
“A number of studies have suggested that cardiopulmonary bypass causes permanent neurologic dysfunction or decreases cognition and motor abilities. Our trial did not show a cognitive decline within 1 year after surgery in either group,” they noted.
In an editorial comment, Dr. Eric David Peterson of Duke University Medical Center, Durham, N.C., said the ROOBY study was rigorously conducted, included a broad range of longitudinal clinical end points, and had adequate statistical power to justify its conclusions.
Nevertheless, these findings are “unlikely to end the debate about on-pump and off-pump CABG.” Research has shown that the off-pump approach may be particularly suited to women, the elderly, and people with severe coexisting illnesses, “yet the ROOBY trial enrolled almost entirely men who were on average younger and healthier than typical candidates for CABG,” Dr. Peterson said (N. Engl. J. Med. 2009;361:1897–9).
Critics also may question whether the technical experience of the surgeons and anesthesiologists was adequately adjusted for in the analysis. In more than half of these cases, the primary surgeon was a surgical resident, he noted.
Dr. Shroyer and Dr. Peterson reported no potential conflicts of interest.