ACC: Off-pump and on-pump CABG equally good at 30 days
CHICAGO—Patients who underwent either on-pump or off-pump CABG surgery had similar outcomes at 30 days, according to a late breaking clinical trial presented March 26 at the American College of Cardiology’s 61st scientific session. But with either procedure, operator experience was critical to success, and the results didn’t rule out potential differences in long-term outcomes, said Andre Lamy, MD, of the Population Health Research Institute at McMaster University in Hamilton, Canada.

The superiority of one procedure over the other has been debated for several years. Recently, a Cochrane Review meta-analysis concluded that on-pump CABG provided better outcomes than did off-pump CABG and recommended the on-pump technique as the standard of care. The meta-analysis authors also explored the relationship between funding source and results of individual trials and found trials without industry funding were more likely to find “a significant harmful effect of off-pump CABG whereas trials with high risk of vested interests showed no inferiority of off-pump CABG.”

CORONARY (Coronary Artery Bypass Grafting Surgery Off or On Pump Revascularization Study) is a large, international randomized trial designed to compare the risks and benefits of off-pump CABG to on-pump CABG based on 30-day and five-year analyses. The ACC.12 presentation focused on 30-day results.

The study enrolled 4,752 patients from 79 centers in 19 countries between November 2006 and October 2011. Patients with isolated CABG with median sternotomy who were 70 years old or older and had either peripheral vascular disease, cerebrovascular disease or renal insufficiency were included. Younger patients with an added risk factor such as diabetes were also eligible. Patients were randomized to either receive on-pump CABG (2,377 patients) or off-pump CABG (2,375 patients).

Surgeons had to have more than two years of experience as a staff cardiac surgeon and had performed more than 100 surgeries using either one or both of the CABG techniques. “Only expert surgeons were allowed to participate in the trial,” Lamy said. “Please keep in mind that most surgeons had performed more than 100 procedures in each technique and therefore were experts in both.”

The primary 30-day outcome was a composite of total mortality, stroke, nonfatal MI or renal failure 30 days after randomization. The five-year outcome will add repeat coronary revascularization over a five-year follow-up period.

Secondary efficacy outcomes such as cost effectiveness, recurrent angina, blood transfusions, quality of life and measures at discharge will be available in the near future, Lamy said.

Lamy pointed out that they had data on all patients at the 30-day follow-up. “This is a high-quality trial,” he said.

Patient characteristics were similar in both groups. Incomplete revascularization was more frequent in the off-pump group. “Time in the operating room [4 vs. 4.2 median hours for off-pump vs. on-pump] and time for the initial ventilation with the patient in the IC were longer in the on-pump group [9.6 vs. 11.2 median hours for off-pump vs. on-pump], and this was highly significant,” Lamy said.

There was no difference in angina at 30 days, marginal difference in PCI and more re-do CABG in off-pump group. “For all the reasons to go back to the OR--and that is never a good thing-- there was no difference,” Lamy said.

Any blood transfusion was more frequent in the on-pump vs. the off-pump group (63.3 percent vs. 50.7 percent, respectively). Thirty-seven percent of the on-pump group compared with 26.1 percent of the off-pump group received antifibrinolytics and 2.4 percent of the on-pump group had re-operation for bleeding compared with 1.4 percent of the off-pump group.

“Off-pump was associated less transfusions and re-operation bleeding, less acute kidney injury, less respiratory infections and failure and more revascularizations,” Lamy summarized.

But there were no differences at 30 days between the two groups in the primary outcome, with 9.8 percent of the off-pump group experiencing death, stroke, MI or renal failure compared with 10.3 percent of the on-pump group. “We believe both are reasonable options,” he said.

At the study's press conference presentation, Lamy described the findings as neutral. “The benefits were balanced, and [each technique] is good in expert hands.”

Lamy suggested that differences in mortality at 30-days may translate into significant differences in the long-term outcomes. The five-year results are expected to be available in 2016.

Panelist Robert A. Guyton, MD, of the division of cardiothoracic surgery at Emory University School of Medicine in Atlanta, followed up with a reference to the recently published Cochrane Review. “The recent Cochrane systematic review suggested there was a mortality benefit for on-pump surgery; particularly, at the end of the review, it cited your study and said we eagerly await the results to be presented at ACC.”

Guyton added surgeon preference may have been a factor in the CORONARY trial. “There often is local enthusiasm or expertise for one technique or the other and it is very difficult to accommodate that local expertise as we try to say which technique is best." He pondered whether there was a possible bias introduced in the recruitment of sites.

Guyton later explained to Cardiovascular Business that a snowball effect can occur at institutions where surgeons favor one technique over the other. That may include infrastructure and support staff who also gain a higher level of comfort and capabilities in the favored technique. In turn, the less favored technique may become a stepchild at the institution.

In response to Guyton’s comment, Lamy replied that the researchers screened sites to ensure high quality. He noted that they recruited sites with proven expertise in both techniques. “Many of the surgeons were like me, and have done hundreds of these procedures.”

The study results were published March 26 online in the New England Journal of Medicine. The CORONARY trial was completely funded by the Canadian Institutes of Health Research, a federal agency.