Heart bypass trial finds better outcomes with standard 'on-pump' method
The topic has been hotly debated among surgeons and cardiologists: Is it safer and more effective to do bypass surgery with or without a heart-lung pump that allows doctors to stop the heart while they operate?
A clinical trial at 18 VA medical centers has found that while both methods are generally safe and effective, the more traditional on-pump method yields better outcomes after one year. The findings appear in the Nov. 5 New England Journal of Medicine.
"There was good survival in both groups at one year, but the conventional method proved safer and somewhat more effective than the newer off-pump method," said study co-leader Frederick Grover, MD, a heart surgeon with VA and the University of Colorado.
After a year, patients in the on-pump group fared better on a composite measure that included death, repeat cardiac procedures, or nonfatal heart attacks. Their vein grafts were also more likely to remain open. The study included follow-up angiograms performed by cardiologists who were "blinded" as to which type of bypass the patients had undergone.
Findings at a glance
- At 30 days, there were no significant differences between groups on a composite measure that included death or major complications.
- At one year, patients in the off-pump group had worse composite outcomes and poorer graft patency.
- There were no significant differences between the groups in neuropsychological outcomes or use of major resources.
In particular, Grover pointed to the fact that both groups scored equally well a year after surgery on neuropsychology tests. Some experts have believed the on-pump method is riskier for cognitive health.
According to first author A. Laurie Shroyer, PhD, the findings of the large, multisite VA study contradict findings from earlier studies that showed "some advantages of [heart bypass] surgery using the off-pump procedure, including quicker recovery and less impact on cognitive function. This study indicated a consistent trend toward better outcomes in patients who had undergone the conventional on-pump technique."
The 2,203 veterans in the study all had clogged or narrowed coronary arteries, resulting in less blood flow to the heart. This can cause chest pain and increase the risk of heart attack. In bypass surgery, also known as coronary artery bypass grafting (CABG), doctors take a healthy piece of vein from elsewhere in the body and sew it in place as a "detour" between the heart and a point in the problem artery below the blockage. As long as the graft remains open—"patent," in medical terms—and doesn't close down over time, the heart enjoys a renewed flow of blood and oxygen.
About the trial
- The study included 2,203 veterans: 99 percent men, 84 percent white, average age 63.
- Two-thirds of the participants had blockages in at least three arteries.
- A third of the participants were current smokers.
- VA doctors who performed off-pump surgeries in the study—the more technically demanding of the two methods—had done an average of 120 such procedures.
- The study ran from 2002 to 2008 and was funded by VA's Cooperative Studies Program.
- The study leaders were Frederick Grover, MD, Denver VA Medical Center; A. Laurie Shroyer, PhD, Northport (NY) VA; Dimitri Novitzky, MD, Tampa VA; and Gerald McDonald, MD, VA Central Office.
For more than 30 years, most bypass procedures have been done with the use of a cardiopulmonary bypass pump, or heart-lung machine. During an "on-pump" procedure, the heart is stopped with medication and the machine takes over blood circulation. This allows doctors to work on a still heart.
An alternative, "off-pump" method that has gained some popularity in the past decade is also known as "beating heart" surgery. As the name implies, the heart keeps beating during the procedure and no heart-lung machine is used. Doctors use special devices to stabilize only the small section of the heart where they are stitching in the graft.
Controversy has existed as to which method is safer and more effective. Some studies suggested that using the pump could weaken heart function after surgery, harm the lung and kidneys, result in more blood use during surgery and longer hospital stays, and bring on problems with memory and thinking. Many experts came to see the off-pump method as enabling a quick recovery, with lower healthcare costs and less risk of cognitive decline.
Recent studies, though, have raised concerns about the newer procedure as well: Is it too technically difficult? Are surgeons sometimes unable to complete multiple grafts on a patient? Are the grafts more likely to fail? And as a result, are patients more prone to heart attacks or repeat procedures?
No studies to date have been conclusive, but the new VA trial results should greatly inform the debate. Grover said he thinks the results may influence cardiology referrals and cardiac surgery practice, but he stresses that individual patient differences still need to be taken into account. Patients with certain risk profiles and patterns of coronary damage, he said, may still be strong candidates for the off-pump method, notwithstanding the general results seen in the trial.