Heart stents, the tiny metal tubes used to prop open diseased arteries, offer only a short-term advantage over drugs in easing pain and fatigue, according to a study that suggests one-third of the 1 million stents used in the U.S. each year may not be needed.

Anti-cholesterol medication used with exercise and dietary changes gave patients equal relief after three years, though stents provided an "incremental" advantage early on, researchers said in today's New England Journal of Medicine. An accompanying editorial said doctors treating clogged arteries where a heart attack isn't a serious risk should consider stents only after drugs are tried.

The study poses another challenge for the $4 billion-a-year stent industry, led by Johnson & Johnson and Boston Scientific Corp., which is recovering from questions about safety. The market's future depends on whether doctors and insurers embrace the implications of the new data, said Eric Peterson, a Duke University cardiologist who co-wrote the editorial.

"There are a lot of forces, in terms of payment, the influence of manufacturers and all the shiny new devices that are coming on to the market, that are encouraging use," Peterson said in a telephone interview. "There is enormous incentive in the medical industry to put things in patients."

Fridley-based Medtronic and Boston Scientific's Maple Grove-based cardiovascular business make drug-coated heart stents.

The study, tracking 2,287 patients, was the second installment of a seven-year investigation dubbed Courage. Last year, researchers said a regimen of drugs and lifestyle changes worked as well as stents in avoiding deaths and heart attacks.

The findings show that angioplasty "is a safe and effective treatment for patients who have frequent or lifestyle-limiting angina while on medical therapy, said Donald Baim, Boston Scientific's chief medical and scientific officer, in a statement.

"The greater the frequency of angina, the greater the benefit of [stents] versus medical therapy alone, although less symptomatic patients can be well managed" without them, Baim said.