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Off-pump Coronary Bypass Surgery vs. Traditional CABG Is There a Winner?
Abstract & Commentary
By Jonathan Abrams, MD Professor of Medicine, Division of Cardiology, University of New Mexico, Albuquerque Dr. Abrams serves on the speaker's bureau for Merck, Pfizer, and Parke-Davis.
Source: Shrover AL, et al. On-pump versus off-pump coronary-artery bypass surgery. N Engl J Med. 2009;361: 1827-1837
Coronary revascularization without cardiopul-monary bypass has become quite successful, in part because of the belief that off-pump coronary bypass procedures are safer than on-pump surgery. However, the literature is conflicting. Some studies support better outcomes with off-pump coronary revascularization; others do not. This study (the ROOBY Trial) was designed to answer the question whether off-pump or on-pump CABG was safer.
ROOBY was a controlled study performed in 18 VA medical centers, carried out from February 2002 through May 2008. The major outcomes were morbidity and mortality at both 30 days and one year. The secondary outcomes included status of grafting and/or revascularization. Results reported on the primary short-term and one-year events were a composite of death or complications (reoperation, cardiac arrest, coma, stroke, or renal failure) within one year after surgery. The primary long-term endpoint was death or non-fatal MI within one year after surgery. Secondary endpoints included completeness of revascularization, graft patency at one year after surgery, as well as neuropsychological outcomes at one year. A total of 2,203 patients undergoing urgent or elective CABG were assigned to an off-pump or on-pump procedure.
Results: There were no significant differences between off-pump and on-pump CABG in the 30-day composite outcome (7% and 5.6%, respectively, p = NS). At the end of one year, the composite outcome was higher for off-pump than on-pump CABG patients (9.9% vs. 7.4%, p = 0.04). The proportion of subjects with fewer grafts than planned was higher in off-pump patients than in on-pump CABG patients, (17.8% vs. 11.1%, p = 0.001). The rate of graft patency was lower in the off-pump cohort as compared to the on-pump group (82.6% vs. 87.8%, p = 01). Importantly, there was no difference in neuropsychological outcomes. Shrover et al concluded that the patients in the off-pump group had worse outcomes and less graft patency at one year as compared to the on-pump group, and neuropsychological outcomes were not better in the off-pump group.
Concerns about the adequacy of coronary on-pump revascularization helped drive interest in off-pump CABG. Use of the pump itself has been suggested to have complications, including a systemic inflammatory response, cerebral dysfunction, myocardial dysfunction, and abnormal hemodynamics. These factors contributed to the concept that off-pump procedures were safer. However, subsequent studies have not all concluded that off-pump procedures are safer than on-pump CABG. The ROOBY outcomes are reassuring, particularly for on-pump CABG.
This is an important and useful report, which is consistent with somewhat better cardiovascular outcomes in typical CABG subjects (i.e., men in their 60's with relatively normal LV systolic function who undergo on-pump multivessel CABG revascularization). Overall survival was comparable at one year, but cardiac deaths were lower in the on-pump group, possibly indicating better and more complete revascularization.
It is likely that both sides of the controversy will continue the dialog of which approach is superior. What is clear is that the ROOBY data and outcomes have resulted in an increased likelihood for outstanding performance. The possible shift to use of the on-pump approach more often and decreased off-pump surgery could change the picture of off-pump CABG I suspect not. The ROOBY study is supportive of both approaches. Experience, good skills, and a careful selection of the patient are likely to result from this publication, but off-pump procedures will continue to be performed by highly experienced surgeons who can replicate or improve on the ROOBY physicians. Also, patient preference for less invasive surgery will continue to drive off-pump surgery.
The statistical difference between the two groups is valid but modest. The issue of residents performing the surgery more commonly in on-pump subjects is interesting and would be expected to tip the results toward the more experienced physicians performing off-pump surgery, but this didn't happen. However, it is unclear how many of the surgeons were closely involved in the procedures. These data may indicate that there was some patient selection during the study that influenced operating room surgeon selection in unstable or difficult subjects. Other studies of this important surgical issue have come to different conclusions. In spite of all the data provided, it is likely that surgical experience, senior surgeon selection, graft selection, and minor differences could have influenced the group data. Thus, it does appear that either approach is reasonable, as long as greater surgical experience and increased skills favor better outcomes. Not all patients are alike, and one approach does not fit all. Surgeon skill, patient anatomy, and pump preference trump a standardized approach in the operating room. That is good news for all.