Yet the debate will go on, says an American expert, because definitive information about the benefits and risks of off-pump versus on-pump surgery is very difficult to get.
The British study, published in the April 6 issue of The Lancet, pooled data from two randomized trials at the Bristol Heart Institute and found significant advantages for off-pump patients. There was a 12 percent reduction in chest infection, a one-third reduction in red cell transfusions, and a 25 percent reduction in atrial fibrillation, a dangerously irregular heartbeat.Add in a 13 percent reduction in extended hospital stays, and the off-pump surgery reduced the cost of the operation by 25 percent, says Dr. Gianni D. Angelini, chairman of the Bristol Heart Institute.
In the longer run, results were similar for both groups of patients. Overall, 2 percent of the off-pump patients died in the next one to three years, compared to 3 percent in the on-pump group. Those numbers are not statistically significant, Angelini says, but they are important.
More than 800,000 people worldwide have cardiac bypass operations, in which stretches of blood vessels from other parts of the body are used to restore blood flow around clogged portions of coronary arteries. In this country, most will be put on a heart-lung machine, although the proportion of off-pump procedures is rising.
"There has been a lot of controversy, with some people saying that you can reduce the short-term complications but the quality of off-pump surgery is not as good, so you have more problems later," he says. "But if you look at mortality and cognition-related events, at two years there is no difference."
Cognition -- thinking ability -- is an important issue because some studies have shown that many patients who undergo any kind of cardiac surgery suffer some loss. But the evidence about a possible advantage of off-pump surgery in the new report is weak, Angelini acknowledges. It showed a trend toward less brain swelling and damage in off-pump patients, but one that was not statistically significant.
Angelini says the evidence is so convincing that he now does the off-pump procedure for 95 percent of his bypass patients. Overall, he says, at least 60 percent of bypass operations at the Bristol Heart Institute are done off-pump.
However, Dr. Craig R. Smith, chief of cardiothoracic surgery at the Columbia University College of Physicians and Surgeons in New York, who says he is an advocate of off-pump surgery, uses the procedure on just 40 percent of his patients. "In my institution, the overall use is about 30 percent, and in the nation it is closer to 20 percent," he says.
Off-pump surgery is not advisable for people with a certain kind of anatomy that makes heart arteries hard to reach, or for those who need multiple grafts or have heartbeat irregularities, Smith says. He usually tells patients "that I am an advocate for off-pump surgery and if I can do it without the pump, I will." Often, he says, the decision is made in the operating room.
Angelini and Smith agree on two things: The final answer will come from a rigorously controlled study, with all patients randomly assigned to one or the other procedure, and that such a randomized study is extremely difficult to do in the United States.
"We are running a randomized study here, and the biggest problem is maintaining randomization," Smith says. "The surgeons or the doctors or the patients often already know what they want. The published reports all show that if you do off-pump surgery on your best patients, the results are better in that group."
Off-pump surgery appears to be falling out of favor in this country, Smith says. "There was an immediate spike in its use in most institutions two or three years ago, but it has been falling back," he says. "Experience is teaching that there are technical hurdles with the off-pump procedure."
There is some good news in general, Smith says: "There are a bunch of things cooking that now make bypass surgery better for everybody -- better filters, better equipment -- that make it safer for everyone."
What To Do
"There is now very strong evidence that the people who benefit most from off-pump surgery are high-risk patients, those with diabetes, renal failure or lung failure, for example," Angelini says. "Evidence seems to point out that they improve if kept off the pump."