Doing bypass surgery on a beating heart instead of using a heart-lung machine is far more likely to result in clogging of the new arteries within just a few months, a study found.
Three months after so-called off-pump surgery, 12 percent of the grafted blood vessels were blocked, compared with 2 percent in patients whose hearts were stopped while they were hooked up to a heart-lung machine.
A few earlier studies found no difference in blockages.
“We were quite surprised that there was a difference,” said Dr. Natasha E. Khan, who directed the study at London’s Royal Brompton Hospital. “It inserts a little caution into how quickly this technique should be expanded into our everyday practice.”
Overall, the study found that off-pump surgery appears to be as safe as conventional bypass with a heart-lung machine. The major difference was how quickly the grafts became clogged.
Khan said researchers do not know the reason for the difference. Possibilities include the different doses of blood thinners used, the difficulty of the surgery, or that many of the 103 patients had a previous heart attack or diabetes.
“I think it’s going to be very difficult in a small population like this to try to put your finger on what exactly it was that caused the difference,” she said.
Khan said off-pump surgery has not been done long enough or studied in large enough numbers yet to conclude whether it is better or worse, and it could be a decade before the verdict is in.
The study is in Thursday’s New England Journal of Medicine.
In bypass surgery, a heart-lung machine circulates the patient’s blood while surgeons attach new blood vessels to create a detour around clogged arteries.
But the machine is thought to increase the risk of stroke, bleeding, damage to the heart and kidneys and possibly mental decline, because it can dislodge bits of plaque into the blood or cause tiny clots or air bubbles.
To avoid those complications, some surgeons have been doing more challenging off-pump surgery, operating on a slippery, beating heart. Devices that help hold the heart still were developed in the mid-1990s, and now about 9 percent of bypass operations are done without the heart-lung machine.
About 314,000 people nationwide had bypasses done in 2000.
In previous studies, off-pump surgery decreased kidney and heart damage, reduced hospital stays and slightly lowered costs. Research is less clear on whether it prevents the memory loss or mental decline that some bypass patients experience.
The latest study also looked at how well the grafts held up three months after surgery in a group of patients who needed at least three grafts. Most earlier studies had fewer grafts.
Effects on mental function unclear
In the off-pump group, 114 of 130 grafts, or 88 percent, were still working, compared with 127 of 130 grafts, or 98 percent, in the heart-lung machine group.
There was less heart damage in the off-pump group and hospital stays were the same for both groups. There were no deaths; one patient in the off-pump group had a heart attack afterward. The researchers tested mental function but have not yet published the results, which Khan said will be of limited value because of the small number of participants.
The researchers said off-pump surgery may be appropriate for patients who are at high risk of complications from the bypass machine.
Dr. Gus J. Vlahakes, a cardiac surgeon at Massachusetts General Hospital, said off-pump surgery is reserved there for high-risk patients, such as those with lung or kidney disease or diseased aortas.
“Bypasses don’t stay open forever, and there is a small percentage that close early. But in the time frame that they had, that was a significant percentage of graft closure,” he said.
Dr. Sidney Smith, a professor of medicine at the University of North Carolina and a past president of the American Heart Association, said a key question is whether more grafts will stay open as doctors gain experience with the off-pump technique.
The researchers noted it may take longer to learn the procedure than they anticipated.
“It’s a very helpful study giving us important information about a new strategy,” Smith said. “I think this is a technology that is worth pursuing.”