Patients with blocked coronary arteries who opt for heart bypass surgery appear to live longer than those who choose a less-invasive stent procedure, according to a large study comparing the two treatments.

The study found that among patients who had an angioplasty procedure, in which the surgeon clears the blockage using an instrument threaded into the artery and then inserts a wire-mesh stent to keep the vessel open, 20.8 percent died in the first four years after treatment.

For patients who received bypass surgery, in which the chest is opened and a vein from another part of the body is used to create a detour around the blocked artery, the death rate was 16.4 percent four years after treatment.

Patients and doctors tend to choose the less-invasive stent procedure when both treatments are an option. Some research has suggested the two treatments have similar long-term outcomes, while other studies have shown better results with bypass surgery.

The new study, whose results were presented at a meeting of the American College of Cardiology in Chicago, analyzed outcomes for 190,000 U.S. patients using Medicare claims and data from the ACC and the Society of Thoracic Surgeons. The study was funded by the National Institutes of Health.

“Combining data from several large databases, we found that survival was better with coronary surgery than percutaneous coronary intervention,” said Dr. William Weintraub, the study’s lead researcher and head of cardiology at Christiana Care Health System in Wilmington, Delaware. “It does push the needle toward coronary surgery, but not overwhelmingly so.”

He cautioned that bypass surgery is not best for every patient. Different risk levels among patients in the data groups may have contributed to the worse outcomes for angioplasty patients in the study, he said.

Dr. Douglas Weaver, a director of the Edith and Benson Ford Heart and Vascular Institute in Detroit, said the study is another piece of evidence in support of bypass surgery.

“It changes the conversation,” he said in an interview. “I think it will temper the use of stents in patients who are otherwise good candidates for surgery.”

Patients who have extensive artery disease, diabetes or challenging vessel anatomy are among those who tend to do better with bypass surgery, he said.

The number of stent procedures being performed is declining, in part due to research favoring bypass surgery but also because fewer people are being diagnosed with coronary disease due to lifestyle changes and better preventive care, said Weaver, a past president of the ACC.

Abbott Laboratories, Boston Scientific Corp and Medtronic Inc are the leading U.S. manufacturers of heart stents. Johnson & Johnson, a pioneer of the technology, stopped selling heart stents last year after sales declined.

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By Susan Kelly