CORONARY Analysis: High-Risk Patients Do Better With Off-Pump CABG

Marlene Busko

November 03, 2012

TORONTO — Although CORONARY was a neutral trial, additional analysis uncovered a "surprising," possibly counterintuitive, finding: patients with a higher risk of dying from surgery benefited from off-pump CABG, whereas low-risk patients tended to do better with on-pump CABG.

"The smart surgeon will go on-pump for low-risk patients and will go off-pump for high-risk patients," said Dr André Lamy (McMaster University, Hamilton, ON), in a late-breaking-trial session at the Canadian Cardiovascular Congress 2012.

"It's time for off-pump CABG to be mastered by all Canadian cardiac surgeons," he added.

Why Regional Differences in Results With Off-Pump vs on-Pump?

CORONARY looked at 4752 patients in 19 countries who were randomized to on-pump vs off-pump CABG and followed for five years. As reported by heartwire , preliminary results were presented at the March 2012 ACC meeting and published in the New England Journal of Medicine.

The smart surgeon will go on-pump for low-risk patients and will go off-pump for high-risk patients.

There was no difference in the primary composite outcome of total mortality, MI, stroke, or new renal failure at 30 days in the two study arms. The primary outcome was seen in 9.8% of patients in the off-pump arm vs 10.3% of patients in the on-pump arm (hazard ratio [HR] 0.95; 95% CI 0.79–1.14).

A closer look at the data, however, uncovered that the risk of death or MI, stroke, or new renal failure at 30 days was higher with off-pump CABG in two of the study regions (HR 1.12 for China and 1.14 for India). The risk was lower in the other two regions (HR 0.68 for South America and 0.89 for combined North America, Europe, and Australia).

These regional variations were not explained by differences in coronary anatomy or surgeon expertise. In fact, all surgeons in the study were highly experienced.

More Low-Risk Patients Enrolled in India, China

However, the EuroSCORE additive model, which assesses a patient's risk of dying from cardiac surgery based on preoperative variables, did shed light on geographic differences in results.

The percentage of low-risk patients was about twice as high in India (40.7%) and China (36.2%) than in South America (22.8%) or the combined region of North America, Europe, and Australia (20.2%). Low-risk patients with a EuroSCORE of 0 to 2 tended to have more events with off-pump vs on-pump surgery (HR=1.35).

The reverse was also true. Medium- and high-risk patients with a EuroSCORE greater than 3 tended to have fewer events with off-pump vs on-pump surgery (HR=0.87).

"It was a discovery to realize that the low-risk and the high-risk patients were behaving differently," Lamy said. "It was a real surprise--the idea that off-pump was not better for everybody."

However, delving more deeply, it appears to make sense that sicker patients would have poorer outcomes with on-pump CABG. Although on-pump is an "easy" technique, and it is the first method taught to residents, "it is the most unphysiologic state you can imagine!" Lamy said.

"We put you on the heart-lung machine. Your pressure [goes] from 120 over 80 [to] 65--it's flat. We cool you down to 32°C. . . . The sicker you are, the more at-risk you are that you will have more and more events and eventually die."

Off-pump is "a totally different animal." It is technically more difficult, since the surgeon has to lift and rotate the heart while it is still beating. "However, your patient has no impact on [your surgical skill]."

Canadian Experience

To tease out further differences, the team looked at data from the 830 patients enrolled in Canadian centers, which was not a prespecified subgroup.

In the Canadian centers, patients who had off-pump CABG had a significantly lower rate of events compared with patients who underwent on-pump CABG.

Similar to the overall study, Canadian patient outcomes after the two types of surgeries were related to their EuroSCORE values.

Cardiac surgeons need to adapt their techniques to suit their patients, Lamy summarized. For example, "Operating on a 55-year-old man in the morning who is a bit obese and a smoker, you can go off-pump, and then [operating on] his [healthy] 85-year-old father in the afternoon--I would go on-pump," he said.

Tailor the Technique to the Patient

"Although the overall trial was negative around the world, the results in Canada really did underscore that there's a need [for cardiac surgeons] to be facile in both [on-pump and off-pump methods] and to apply the right technique to the right patient," comoderator Dr John Mancini (St Paul's Hospital, Vancouver, BC) told heartwire after the session

"The presenter said one thing that's really important: 'You use the right technique for the right patient,' " echoed incoming president of the Canadian Cardiovascular Society, Dr Mario Talajic (Montreal Heart Institute, QC), when asked for a comment.

"It was counterintuitive to me that taking the worst kind of patient and using a more sophisticated, difficult surgery actually had better outcomes," added comoderator Dr Anthony Tang (University of British Columbia, Vancouver). "I remember when off-pump came along, this was mostly applied to patients who had single-vessel disease--really low-risk patients," he noted. "Now we know to use this on high-risk patients."

The authors declared they have no conflict of interest.