CORONARY Bypass Shows Similar Results Whether On-Pump or Off

CHICAGO, IL—Despite recent reports showing worse results with off-pump—with the heart still beating—coronary artery bypass graft (CABG) surgery as opposed to on-pump, the largest prospective, randomized trial to date comparing the two surgical techniques shows that they achieve similar outcomes at 30 days. Results of the CORONARY trial were presented March 26, 2012, at the annual American College of Cardiology/i2 Scientific Session.

The findings were simultaneously published online in the New England Journal of Medicine.

For the CABG Off or On Pump Revascularization Study (CORONARY), researchers led by André Lamy, MD, of McMaster University (Hamilton, Canada), randomized 4,752 patients to undergo CABG either on-pump (n = 2,377) or off-pump (n = 2,375) at 79 centers in 19 countries. To participate in the study, surgeons had to have more than 2 years of experience and over 100 cases of 1 or both techniques. The rate of crossover from off- to on-pump was 7.9%, while 6.4% crossed over from on- to off-pump (P = 0.06).

Primary Endpoint Equivalent

Fewer grafts were performed per procedure in the off-pump group than in the on-pump group (3.0 vs. 3.2; P < 0.001), and incomplete revascularization occurred more often in the off-pump group, though the difference just reached statistical significance (11.8% vs. 10.0%; P = 0.05). Blood product transfusions also occurred less often in the off-pump group (50.7% vs. 63.3%; P < 0.001), while procedure duration was shorter in off-pump patients (4.0 hrs vs. 4.2 hrs; P < 0.001).

At 30 days, the primary outcome of death, nonfatal stroke, nonfatal MI, or new renal failure requiring dialysis was equivalent in both groups, as were each of the component endpoints (table 1).

Table 1. Primary Endpoint and Component Endpoint at 30 Days

 

 

Off-Pump CABG
(n = 2,375)

On-Pump CABG
(n = 2,377)

95% CI

P Value

Primary Endpoint

9.8%

10.3%

0.79-1.14

0.59

Death

2.5%

2.5%

0.71-1.46

Stroke

1.0%

1.1%

0.51-1.54

MI

6.7%

7.2%

0.75-1.15

New Renal Failure

1.2%

1.1%

0.61-1.76

 

The primary endpoint and all component endpoints remained equivalent across multiple subgroups analyzed.

There were reductions in numerous secondary outcomes with off-pump CABG, including acute kidney injury, respiratory failure or infection, ventilator times, and reoperations for bleeding, though off-pump patients saw more early repeat revascularizations (table 2).

Table 2. Secondary Outcomes

 

 

Off-Pump CABG
(n = 2,375)

On-Pump CABG
(n = 2,377)

P Value

Acute Kidney Injury ≥ Stage 1

28.0%

32.1%

0.01

Ventilator Time, hrs.

9.6

11.2

< 0.001

Reoperation for Bleeding

1.4%

2.4%

0.02

Repeat Revascularization

0.7%

0.2%

0.01

Respiratory Failure or Infection

5.9%

7.5%

0.03

 

The authors were surprised at the lack of stroke reduction in the off-pump group, since the embolic risk from aortic cannulation and cross-clamping that occurs with the on-pump technique is not present with off-pump CABG.

Dr. Lamy and colleagues note that the CORONARY results are similar to those of the 30-day findings from the ROOBY trial, published in 2009, which also compared off-pump and on-pump CABG. However, ROOBY showed worse results with off-pump CABG. Likewise, as recently as March 14, 2012, a Cochrane Database meta-analysis published on line found that off-pump CABG was associated with an increase in mortality.

Both Procedures ‘Reasonable Options’ with Experience

Dr. Lamy noted that long-term follow-up for the CORONARY trial will continue, during which time, “the difference in morbidity that was detected in the 30-day results may or may not lead to significant differences.” But either way, “in experienced hands, both procedures are reasonable options based on [these] short-term results,” he said.

In an accompanying editorial, Frederick L. Grover, MD, of the University of Colorado School of Medicine (Denver, CO), notes that neurocognitive data, which were collected for CORONARY but not analyzed for the present report, “will have a major influence on the interpretation of the primary trial results.” Unfortunately, though, postoperative coronary arteriography was not performed, an important limitation.

“However, the true relative efficacy and durability of off-pump CABG will probably be determined by longer-term follow-up,” Dr. Grover writes.

Noninferiority Does Not Equal Superiority

Robert A. Guyton, MD, of the Emory University School of Medicine (Atlanta, GA), called the CORONARY results “very important,” but added that the trial design terminology and results may have been misleading. “It’s a superiority trial that failed to show the superiority of off-pump surgery,” he said. “Therefore, the conclusion probably needs to state that there’s no significant difference detected. You can’t claim that there’s no difference between the two in this trial. If you had to do this over again, the question is whether or not you might set this up as a noninferiority trial rather than a superiority trial.”

To which Dr. Lamy replied: “There are benefits on both sides, the results are truly neutral.”

Dr. Guyton also raised the question as to whether sites enrolled in CORONARY were “enthusiastic supporters” of off-pump CABG, which may have skewed the results.

“These sites are enthusiastic cardiac care research sites,” Dr. Lamy answered. “We recruited centers with expertise in both techniques. Some probably were more enthusiastic toward off-pump surgery, but many surgeons like me have done hundreds of both procedures.”

Dr. Lamy also addressed the recent negative studies, noting that the Cochrane meta-analysis may have been the result of a single small study with a 25% mortality rate in the off-pump surgery arm. “That study completely shifts the results of the analysis,” he said.

Dr. Lamy added that he actually agrees with the conclusions of the ROOBY trial, which was conducted in the Veterans Administration (VA) system. “In the VA system, you should probably not do off-pump surgery,” he said.

Sources:

  1. Lamy A, Devereaux PJ, Prabhakaran D, et al. Off-pump or on-pump coronary-artery bypass grafting at 30 days. N Engl J Med. 2012;Epub ahead of print.
  2. Grover FL. Current status of off-pump coronary-artery bypass. N Engl J Med. 2012;Epub ahead of print.

Disclosures:

  • The study was funded by the Canadian Institutes of Health Research.
  • Dr. Lamy reports no relevant conflicts of interest.
  • Dr. Grover reports serving as a principal investigator of the ROOBY trial.

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