According to a study published in the New England Journal of Medicine, no significant differences in short-term outcomes were seen in patients who underwent coronary artery bypass grafting (CABG) with a heart-lung machine (on-pump) or without the machine (off-pump). At 1 year, the off-pump group had significantly worse morbidity, mortality, and graft patency with no difference in cognition noted between the 2 groups.
There is ongoing controversy as to whether off-pump CABG reduces postoperative complications, including neurologic deficits and hemodynamic instability. Therefore, the Randomized On/Off Bypass (ROOBY) trial was designed to compare differences in morbidity and mortality at 30 days and 1 year in patients randomized to CABG on-pump (n=1104) or off-pump (n=1099). The study took place at 18 Veterans Administration centers from February 2002 through May 2008; the participants were nearly all men (99.4%), with an average age of 62 to 63 years; 65% to 68% of the participants in both groups had 3-vessel coronary disease. The primary short-term endpoint was a composite of death or complications before discharge or within 30 days of surgery. The primary long-term endpoint was a composite of death from any cause, additional revascularization procedures, or a nonfatal myocardial infarction (MI) within 1 year of surgery. The secondary endpoints included graft patency at 1 year, cognitive outcomes, and the use of healthcare resources such as postoperative length of stay and time spent on a ventilator.
After 30 days, off-pump patients had higher 30-day composite mortality and morbidity rates compared with those who underwent traditional, on-pump procedures (7.0% versus 5.6%; P=0.19). After 1 year, patients who underwent off-pump CABG had a significantly higher composite 1-year mortality from any cause, repeat revascularization, or nonfatal MI (9.9% versus 7.4%, relative risk [RR], 1.33; P=0.04). The 1-year cardiac death rate was also higher with off-pump procedures (2.7% versus 1.3%; P=0.03). At 1 year, off-pump grafts were less likely to remain patent on follow-up angiograms (82.6% versus 87.8%; P<0.01). At 1 year, baseline and follow-up cognitive data were available for 892 patients in the off-pump group and 1099 patients in the on-pump group with no significant difference noted in neurocognitive scores in either group (P=0.21).
The study was limited by the population, which was younger and healthier than typical patients likely to undergo CABG. In addition, less than 1% of the patients were women, a population thought to benefit from the off-pump procedure. Although the surgeons were required to have experience with at least 20 prior off-pump procedures, it may require many more than 20 procedures to achieve expertise. While the ROOBY trial did not support the hypothesis that off-pump CABG provides better outcomes compared with on-pump surgery, ongoing clinical trials may yet elucidate a subset of patients who will benefit from off-pump surgery. Until then, there is a paucity of clinical evidence to support the use of off-pump CABG as standard care.