Results from coronary bypass operations are similar whether they are performed while the heart is stopped or beating, the American Heart Association said yesterday.

Off-pump bypass, with the heart beating slowly, is performed at Emory Crawford Long Hospital in Atlanta.

The advantage of using one bypass technique over the other is one of the most hotly debated issues in heart surgery. To try to find an answer, the heart group assembled a team of cardiac surgeons, cardiologists, anesthesiologists and neurologists to review what the experts called the best data from clinical trials. The team included proponents and opponents of each type of operation.

But no clear evidence emerged that one technique was better than the other, the team reported in the May 31 issue of the heart group's journal, Circulation.

In a bypass operation, surgeons construct grafts from arteries and veins to reroute blood around clogged arteries to relieve chest pain and reduce the risk of a heart attack.

The operation can be performed by two techniques - stopping the heart or allowing it to beat.

The beating-heart technique is used in about 20 percent of bypass operations. In them, surgeons sew the grafts in place while the heart beats slowly.

In the stopped-heart version, surgeons connect a patient to a heart-lung machine that pumps blood through the body until the heartbeat is restored. The on-pump technique is the more traditional type of bypass operation.

The team surveyed hundreds of studies of the two techniques that involved tens of thousands of patients and were published in peer-reviewed journals. Many studies were excluded because of flaws, and some "authors wanted to show that one technique is better than the other," making the findings biased, said the leader author of the team, Dr. Frank W. Sellke, chief of cardiothoracic surgery at the Beth Israel Deaconess Medical Center in Boston.

A review of the best studies found advantages and disadvantages for each type of operation, but no overall difference in rates of survival.

"Patients may receive an excellent outcome with either type of procedure," the experts said, but the outcomes "likely depend more on factors other than" the type of bypass procedures the patients had.

The skill of the surgical team and quality of the hospital play a much greater role in determining results than the type of procedure, the team said.

The death rate ranged from less than 1 percent to more than 6 percent in most studies.

Surgeons can generally learn the on-pump operation faster than the off-pump technique because it is technically less demanding. Also, the report said, surgeons can generally perform more grafts, if necessary, in an on-pump bypass, and the grafts may stay open longer.

The reviewers said off-pump bypasses probably had more short-term benefits like less blood loss and need for transfusion. There were also shorter hospital stays with off-pump operations.

A controversy has developed over some evidence that a small but significant number of on-pump bypass patients suffer a degree of cognitive impairment like memory and attention deficits and language problems. Such problems tended to occur less among patients whose bypasses were performed with the beating-heart technique compared with the stopped-heart technique, the team said. The extent of the decrease was not detailed.

When surgeons had to switch patients from an off-pump to an on-pump grafting during surgery, patients had a much greater risk of failure of several organs and death compared with patients who initially had on-pump bypasses, the report said.

Bypass surgery is lucrative for many hospitals. The cost of the two procedures is comparable, from $22,000 to $35,000, depending on the surgeons and hospitals, Dr. Sellke said, adding, "It's hard to actually come up with an exact figure on the cost of the surgery, because nobody really does careful accounting."

The most conclusive benefit of off-pump over on-pump operations was for patients who had deposits of calcium in their aortas, the body's main artery. When surgeons clamp the aorta in the on-pump technique, small pieces can break off to cause disabling and fatal strokes.

A large rigorously controlled randomized trial is needed to determine definitively which method is superior. Such trials are difficult, the report said, in part because the surgical team knows which patient received which type of operation, possibly making the findings biased.

The Veterans Affairs Department has started one such study, but findings are not expected for several years. Even then, Dr. Sellke said, the findings may not be representative of patients in community hospitals because most participants will be elderly male veterans.