More than half a million people a year with chest pain are getting an unnecessary or premature procedure to unclog their arteries because drugs are just as effective, suggests a landmark study that challenges one of the most common practices in heart care.

The stunning results found that angioplasty did not save lives or prevent heart attacks in non-emergency heart patients.

An even bigger surprise: Angioplasty gave only slight and temporary relief from chest pain, the main reason it is done.

“By five years, there was really no significant difference” in symptoms, Buffalo General Hospital’s Dr. William Boden said. “Few would have expected such results.”

He led the study and gave results yesterday at a meeting of the American College of Cardiology. They also were published online by the New England Journal of Medicine and will be in the 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 nonemergency basis, to relieve chest pain caused by clogged arteries crimping the heart’s blood supply.

Those patients now should try drugs first, experts say. If that does not help, they can consider angioplasty or bypass surgery, which unlike angioplasty, does save lives, prevent heart attacks, and give lasting chest pain relief.

In the study, only one-third of the people treated with drugs ultimately needed angioplasty or a bypass.

“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, a Cleveland Clinic heart specialist and president of the College of Cardiology, Dr. Steven Nissen, said.

Why did angioplasty not help more?

It fixes only one blockage at a time whereas drugs affect all the arteries, experts said. Also, the clogs treated with angioplasty are not the really dangerous kind.