As the world's population ages, surgery to replace the arteries of the heart is becoming more common. But some people do not survive artery bypass surgery, or suffer other complications. Now, a major international study shows that inexpensive aspirin can improve their prospects.

Doctors perform about one million coronary bypass operations around the world each year. Although there have been major technical advances in the procedure, about 15 percent of the surgeries end in death, heart attack, stroke, kidney failure, or other complications.

But a study of 5,000 such operations in 17 countries in North and South America, Europe, the Middle East, and Asia shows that the common aspirin pill can combat these problems. "Aspirin taken immediately after surgery can prevent these complications," said Dennis Mangano.

This is physician Dennis Mangano of the Ischemia Research and Education Foundation in San Francisco. He led the multinational study, which appears in the New England Journal of Medicine. "This is the first time that a therapy has ever been identified that can prevent some of the complications associated with this life saving procedure called heart bypass surgery," he said.

The international team found that patients who received up to 650 milligrams of aspirin within two days of bypass surgery were one third as likely to die as the other patients. They were also half as likely to suffer a heart attack or stroke, and one fourth as likely to experience kidney failure.

A surprising finding was that patients who stopped taking aspirin before surgery were more likely to die than those who kept taking it were.

This counters conventional medical thinking. Surgeons have been reluctant to administer aspirin before and after bypass operations for fear that its anti-clotting properties would cause internal bleeding. But Dr. Mangano's group found that the aspirin recipients experienced less internal bleeding than the others did. "Our finding indicates that one or two aspirin does not produce any more bleeding or any other side effects and is very safe," he said.

Doctors frequently prescribe aspirin to prevent heart attacks in people at high risk for them or for those who have already suffered one. But the American Heart Association says aspirin therapy should be stopped for one week or more before bypass surgery. Experts say the new study should change this guideline and current surgical practice.

Dr. Eric Topol is the head of cardiology at the Cleveland Clinic, a leading U.S. heart surgery center. "The benefits are profound, improving survival, avoiding virtually every complication or reducing the complications that are serious to a great magnitude, and also less bleeding," said Eric Topol. "So all these things are terrific."

But Dr. Topol says the study findings might be exaggerated for two reasons. First, the patients were not chosen randomly for aspirin therapy. Instead, the surgeons made the choices, which could have influenced the results. Second, he says only better hospitals give aspirin to heart patients. Therefore, the differences in the quality of care among the hospitals might also have affected the outcome.

But Dennis Mangano says these limitations are outweighed by the uniform findings throughout 17 nations. "Although conservatively we should wait for a randomized trial, the prudent decision is to start aspirin in every patient," said Dennis Mangano.