CORONARY: Off-Pump and on-Pump CABG Give Similar Short-Term Outcomes

March 26, 2012

March 26, 2012 (Chicago, Illinois) — The largest study ever to compare off-pump and on-pump CABG has shown no significant difference in 30-day results for the primary end point [1]. Some differences in secondary end points may drive decisions on an individual basis until long-term results are available, suggests the lead author.

The CORONARY study was presented at the American College of Cardiology (ACC) 2012 Scientific Sessions today and simultaneously published online in the New England Journal of Medicine.

Lead investigator Dr André Lamy (McMaster University, Hamilton, ON) explained that previous trials and meta-analyses of studies comparing off- pump and on-pump CABG have shown conflicting results, and there is a need for a large high-quality study to settle the issue. "The CORONARY study should do that," he told heartwire .

"Our study should settle the current controversy surrounding off-pump surgery. The recent results suggesting worse outcomes with this approach were probably due to inexperienced surgeons. As off-pump is more technically challenging, you need to be more experienced for this approach, but if the surgeon is comfortable with off-pump, the results seem to be good."

The CORONARY trial randomized 4752 patients in whom CABG was planned to off-pump or on-pump surgery. There was no significant difference in the primary end point, a composite of death, MI, stroke, or new renal failure requiring dialysis at 30 days after randomization. There was also no difference in any of the individual components of the primary end point.

CORONARY: Primary Composite End Point and Individual Components

End point Off-pump (%) On-pump (%) HR (95% CI)
Primary composite end point 9.8 10.3 0.95 (0.79–1.14)
Death 2.5 2.5 1.02 (0.71–1.46)
MI 6.7 7.2 0.93 (0.75–1.15)
Stroke 1.0 1.1 0.89 (0.51–1.54)
New renal failure 1.2 1.1 1.04 (0.61–1.76)

There were, however, some differences in secondary outcomes, with the off-pump group showing advantages of less bleeding, respiratory infections, and acute kidney injury, but this group also had fewer grafts performed and had more revascularizations.

CORONARY: Secondary Outcomes

End point Off-pump (%) On-pump (%) HR (95% CI)
Repeat revascularization 0.7 0.2 4.01 (1.34–12.0)
Respiratory failure or infection 5.9 7.5 0.79 (0.63–0.98)
Acute kidney injury 28.0 32.1 0.87 (0.80–0.96)
Blood transfusion 50.7 63.3 0.80 (0.75–0.85)
Reoperation for perioperative bleeding 1.4 2.4 0.61 (0.40–0.93)

Lamy commented to heartwire : "These secondary findings may have a big impact on long-term follow-up. We are continuing to follow patients for five years, and I think our long-term results will be very interesting."

Consider a Personalized Approach

He suggested that for the time being, either approach could be used. "I would recommend that surgeons train in both methods and consider these results when deciding which method to use for each individual patient. So we are thinking about personalized medicine."

He continued: "For example, if the surgeon were equally competent at both techniques, for an 83-year-old woman of 50 kg and some kidney dysfunction, I might choose off-pump, as that seems to be associated with less transfusion and kidney problems, but for a 62-year-old diabetic smoker with diffuse disease, on-pump may be a better option to get the best revascularization possible."

He added that patients with a calcified aorta are definitely better off getting off-pump, as it is difficult to cannulate the aorta in these cases. "But we often don't know this until they are on the table, so it is good to be trained in both techniques."

Lamy noted that the proportion of off-pump vs on-pump procedures varies with geographical location and individual centers. In the US and Europe, most CABGs are done on-pump now, as this is the easiest method. But in South America, China, and India, off-pump is more popular, probably because it is cheaper not to use a pump.

Surgeon Experience Critical Especially for Off-Pump

He explained that the main factor that can influence outcome is the surgeon's experience in each method, but this is probably more important in off-pump procedures, as this approach is so much more challenging because the heart is still beating. And many previous studies may not have controlled for differences in surgeon experience.

"In our study we insisted all surgeries were conducted by experienced surgeons. They had to have performed at least 100 cases in the approach used. But in fact, we found that the vast majority of surgeons involved in our study were very experienced in both approaches."

Lamy explained that for many years meta-analyses of studies comparing the two strategies have shown similar outcomes for off-pump vs on-pump, with maybe a trend toward benefit of off-pump.

But a large study in 2009--the ROOBY trial--suggested a worse outcome with off pump. And a Cochrane review just published suggested a higher death rate with off-pump.

But Lamy says his study is the best evidence to date and should override both the ROOBY trial and Cochrane review. "With 5000 patients, we have more patients than any other study, and we included 79 centers worldwide, with all cases being done by experienced surgeons. This is very high quality."

He also pointed out that the ROOBY study was conducted only in VA hospitals, which have a high proportion of trainee surgeons. "So expertise would have been lower in this study, which would affect off-pump more."

And Lamy noted that the new Cochrane review included just one additional study to the most recent meta-analysis by Afilalo [2], which showed a trend toward benefit with off-pump. "That one additional study [3], which was conducted by one of the authors of the Cochrane review, was small, with only about 300 patients, and had a very high mortality rate (around 25%) in the off-pump group. This one study completely skewed the results of the review to suggest harm with off-pump surgery. I would suggest that a more sensible interpretation of that one small study would be that surgeons involved in that study shouldn't be doing off-pump procedures. But our results are far more reliable and suggest that with experienced surgeons, both techniques are similar in terms of short-term outcomes."

Speculating on why off-pump surgery may be associated with some of the better secondary outcomes, Lamy explained that the pump takes away diastolic and systolic blood pressures, instead producing one constant pressure, and this may be responsible for the acute kidney injury. He added that this has also been suggested to contribute to the neurocognitive dysfunction sometimes seen after bypass surgery. The CORONARY trial included a neurocognitive substudy to look at this issue further, but these results are not available yet.

In an editorial accompanying the paper [4], Dr Frederick Grover (VA Medical Center, Denver, CO) notes that the CORONARY trial included higher-risk patients than the ROOBY study, who are thought to derive a greater benefit from off-pump surgery. He concludes that long-term results from the CORONARY trial "should shed more light on this controversial topic and on specific subgroups of patients who might benefit from off-pump CABG."


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