If you've been diagnosed with a clogged artery in your heart, there's a good chance your doctor recommended angioplasty. That procedure involves first clearing out the blockage and then propping the artery open with a tiny cylindrical device called a stent.

Close to a million stents are inserted in people in the U.S. annually to open up blocked coronary arteries, according to the most recent evidence available. Yet researchers have known for more than a decade that angioplasty usually saves lives only if done immediately after a heart attack.

Here's what you should know about when angioplasty and stents are necessary and when they aren't.

The History of Angioplasty

Angioplasty, which first became widely available in the 1980s, gained steam after its effectiveness as an emergency treatment for heart attacks became clear.

More on Heart Procedures

In angioplasty, also called percutaneous coronary intervention (PCI), the doctor inflates a thin balloon in the narrowed artery to crush deposits, leaving a stent in place to keep the vessel open.

When performed within hours of a heart attack to clear a blocked or nearly blocked artery, it's clear that angioplasty can be lifesaving.

When You Do (and Don't) Need It

“Thirty years ago, doctors made the assumption that since [angioplasty] could help with a heart attack, it would help with other blockages due to coronary-artery disease,” says David Brown, M.D., a cardiologist and professor of medicine at the Washington University School of Medicine in St. Louis.  

But a pivotal clinical trial of 2,287 people with stable heart disease, published in the New England Journal of Medicine in 2007, found that having a stent implanted didn’t reduce the risk of death, a heart attack, or other major cardiovascular events when added to a patient’s drug therapy. Subsequent studies had similar results.

And while the number of stents has declined significantly since that study was published, a 2015 study by Yale University researchers in the Journal of the American Medical Association found that of 2.7 million angioplasties performed over a five-year period, 13 percent of nonemergency stents were still considered inappropriate.

One explanation for the continued use is that the procedure—which is relatively quick and easy—is seen as a moneymaker for doctors and hospitals, says Brown, who has written about the overuse of the procedure.

But in nonemergency situations, lifestyle changes—plus medications to control blood pressure, lower cholesterol, and prevent blood clots—are at least as effective and usually safer. A December 2016 review in JAMA Internal Medicine found that approach could reduce the number of angioplasties by 80 percent.

Another recent study, first published online in November 2017 in the Lancet, raised questions about whether stents should be used so often (or at all) to treat chest pain. In patients with medically treated angina and severe narrowing of the arteries, this small study—which still needs to be replicated by larger studies—found that angioplasty was no more effective than a sham procedure at relieving symptoms of angina. 

The upshot: In most cases, you don’t need a stent unless you’re having a heart attack or have severe angina (chest pain) that doesn’t respond to medical therapy