After five years, the bypass group had a lower combined rate of heart attacks, strokes and deaths of 18.7 percent versus 26.6 percent for the stent group in the 1,900-patient study funded by the U.S. National Institutes of Health.
Previous studies had demonstrated the superiority of bypass surgery over the use of bare metal stents - tiny mesh tubes used to prop open cleared arteries. Researchers suspected that newer stents coated with drugs to prevent reclogging might negate some of the bypass advantage, but that turned out not to be the case.
"The advantages were striking in this trial and could change treatment recommendations for thousands of individuals with diabetes and heart disease," said Dr. Valentin Fuster, from Mount Sinai School of Medicine in New York, who presented the findings at the American Heart Association scientific meeting in Los Angeles.
There was a higher incidence of stroke in bypass patients -- 5.2 percent versus 2.4 percent. Stroke is a known risk of the surgical procedure in which a piece of a healthy blood vessel from another part of the body is grafted on to re-route blood flow around a blocked heart artery.
But deaths from any cause were significantly lower with bypass surgery than those who received artery clearing angioplasty and a drug eluting stent - 10.9 percent compared with 16.3 percent. There were also twice as many heart attacks among diabetics in the stent group within five years - 99 vs 48, which Fuster called "very significant."
More than one million bypass surgeries or stenting procedures are performed in the United States each year and some 25 to 30 percent of those involve diabetics with multiple diseased arteries, researchers said.
If the results of this study alter clinical practice, it could eat into lucrative profits of the companies that sell drug coated stents, such as Abbott Laboratories, Boston Scientific Corp and Medtronic Inc. Boston Scientific and Johnson & Johnson supplied the stents used in the study, but J&J has since exited the stent business.
Dr. David Williams of Brigham and Women's Hospital in Boston, who was not involved in the study, called the results "very convincing."
"I think the (treatment) guidelines will recognize this and I do think it will be adopted," he said.
However, Fuster cautioned that longer term follow-up of patients was necessary.
"We always want to know how long the effects last," he said. "The gap could begin to close or the results could get better and better."
(Editing by Marguerita Choy)