30-Day Outcomes of Off-Pump and On-Pump CABG

For patients with extensive coronary artery disease, mortality can be reduced through coronary-artery bypass grafting (CABG), a procedure generally performed using cardiopulmonary bypass (on-pump). Use of the on-pump approach results in approximately 2% perioperative mortality; an additional 5% to 7% of patients have complications that include infarction, stroke, and renal failure necessitating dialysis. The technique of operating on a beating heart (off-pump) was developed to decrease the rate of perioperative complications.

Previous studies, including the ROOBY (Randomized On/Off Bypass) trial, compared the 2 approaches to CABG. ROOBY enrolled 2203 patients from the Veterans Affairs medical system. However, according to researchers, the previous trials did not have sufficient power to accurately assess moderate but clinically important differences in rates of death, myocardial infarction (MI), stroke, and renal failure. In addition, surgical expertise, particularly for the off-pump approach, varied in the earlier studies.

The researchers recently conducted a larger trial in a range of hospital settings with specific requirements for surgical expertise, to compensate for some of the limitations in the initial trials. Results of CORONARY (CABG Off or On Pump Revascularization Study) were reported online in the New England Journal of Medicine [doi:10.1056/NEJMoa1200388].

The primary hypothesis of CORONARY was that off-pump CABG, compared with on-pump CABG, would reduce the rate of major clinical events in the short term (30 days) and that the benefits would be maintained in the long term (5 years).

The study was conducted at 79 centers in 19 countries. Researchers randomly assigned 4752 patients who were scheduled to undergo CABG to either off-pump or on-pump. The coprimary outcome was a composite of death, nonfatal stroke, nonfatal MI, or new renal failure necessitating dialysis at 30 days after randomization. The second was the first coprimary outcome plus repeat coronary revascularization at a mean of 5 years.

Secondary and tertiary outcomes included rates of blood transfusion, recurrent angina, death from cardiovascular causes, and the first coprimary outcome at the time of discharge after CABG surgery.

Of the 4752 patients, 2375 were assigned to undergo off-pump CABG and 2377 to undergo on-pump CABG. Baseline characteristics were similar in the 2 groups; the mean age was 68 years and 81% were male. One third of the total cohort had had a previous MI. There were 34 patients who did not undergo the surgery. There were some crossovers between the groups: 7.9% (184/2332) who were assigned to the off-pump group actually underwent on-pump surgery and 6.4% (150/2333 who were assigned to on-pump underwent off-pump surgery (P=.06).

Compared with the on-pump group, there were fewer grafts performed in the off-pump group (3.2 vs 3.0, respectively; P<.001), and the rate of incomplete revascularization was higher (10.0% vs 11.8%; P=.05). The off-pump procedure was associated with shorter operations (4.0 hours vs 4.2 hours; P<.001) and shorter duration of ventilator support (9.6 hours vs 11.2 hours; P<.001).

The primary outcome at 30 days occurred in 9.8% (n=233) of the patients in the off-pump group and 10.3% (n=245) in the on-pump group. There was no significant difference between the 2 groups in the individual components of the composite outcome.

The use of the off-pump procedure compared with on-pump CABG did significantly reduce the rates of blood-product transfusion (50.7% vs 63.3%, respectively; P<.001), reoperation for perioperative bleeding (1.4% vs 2.4%; P=.02), acute kidney injury (20.8% vs 32.1%; P=.01), and respiratory complications (5.9% vs 7.5%; P=.03). The rate of early repeat revascularizations was increased, however (0.7% vs 0.2%; P=.01).