Opening up blocked arteries using angioplasty is no better at preventing future heart attacks than treatment with a combination of heart drugs, good diet and exercise, suggests a landmark study that challenges one of the most common practices in heart care.

The findings could change the standard of practice with heart patients, making angioplasty a procedure cardiologists resort to only if drugs and lifestyle changes don't work.

Researchers in the United States and Canada studied 2,287 patients, giving roughly half of them angioplasty, a procedure where a blocked artery is opened up by threading a small balloon to the site and then expanding it.

The other half of the participants were told to take heart drugs like statins to lower their bad cholesterol levels and to exercise.

After following the patients for a number of years, the researchers found there was no real difference between the two groups' rates of deaths caused by heart disease, heart attacks or strokes.

Both groups experienced a major reduction in chest pain, though the improvement was greater in the patients who had undergone angioplasty.

The findings were revealed Monday in New Orleans at the American Cardiology Conference and were published online by the New England Journal of Medicine ahead of its April 12 issue.

Angioplasty remains the top treatment for people having a heart attack or hospitalized with worsening symptoms. But most angioplasties are done on a non-emergency basis, to relieve chest pain caused by clogged arteries crimping the heart's blood supply.

"You are not putting yourself at risk of death or heart attack if you defer," and considering the safety worries about heart stents used to keep arteries open after angioplasty, it may be wise to wait, said Dr. Steven Nissen, a Cleveland Clinic heart specialist and president of the College of Cardiology.

Angioplasty may not help more because it fixes only one blockage at a time, whereas drugs affect all the arteries, experts said.

In angioplasty, doctors snake a tube through a blood vessel in the groin and into a blocked heart artery. A tiny balloon is inflated to flatten the clog and a mesh scaffold stent is usually placed to keep it open.

People in the study had an average of 10 chest pain episodes a week, a group with moderately severe symptoms. About 40 per cent had a prior heart attack more than three months previously.

"We deliberately chose to enrol a sicker, more symptomatic group" to give angioplasty a good chance to prove itself, said Dr. William Boden of Buffalo General Hospital in New York, who led the study.

At the start of the study, 80 per cent had chest pain. Three years into it, 72 per cent of the angioplasty group was free of this symptom, as was 67 per cent of the drug group.

Angioplasty costs $30,000 US to $40,000 US. The drugs used in the study are almost all available in generic form.

The study was funded by the U.S. Department of Veterans Affairs, the Medical Research Council of Canada and a host of drug companies. Stent makers refused to help pay for the research, said scientists who led the study.

With files from the Associated Press