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Drug-eluting stents: Do they increase heart attack risk?

Drug-eluting stents and bare-metal stents are often used to treat clogged arteries. A Mayo Clinic doctor compares stents and discusses whether drug-eluting stents increase your heart attack risk.

By Mayo Clinic staff

Photo of Charanjit Rihal, M.D.
Charanjit Rihal, M.D.

In recent years, there has been some concern about the use of some types of popular medical devices called stents. Stents are used to keep arteries open after a procedure called angioplasty. More than 2 million people receive stents each year, including a million Americans.

Some studies have suggested a certain type of stent known as a drug-eluting stent might increase your risk of heart attack. Other studies didn't find much risk.

Charanjit Rihal, M.D., a cardiologist and director of Mayo Clinic's Cardiac Catheterization Laboratory, Rochester, Minn., answers some questions about stents.

What's a stent?

Stents are metal mesh tubes inserted after an angioplasty into an artery that has become partially or completely blocked. Stents help prevent restenosis — when the artery becomes blocked again. Without the use of stents, about 30 percent of arteries become blocked again.

There are two basic kinds of stents: bare-metal stents and drug-eluting stents.

  • Bare-metal stents, as the name implies, are metal stents with no special coating. Bare-metal stents act as simple scaffolding to prop open blood vessels after they are widened with angioplasty. As the artery heals, tissue grows around the stent holding it in place. However, sometimes an overgrowth of this scar tissue in the arterial lining increases the risk that the artery will become blocked again, hence the invention of the drug-eluting stent.
  • Drug-eluting stents are coated with medication that is slowly released (eluted) to help prevent the growth of scar tissue in the artery lining. This helps the artery remain smooth and open, assuring good blood flow through it. Drug-eluting stents were developed because in about 20 percent of those who get bare-metal stents, tissue growth over the stent eventually leads to re-blockage. Drug-eluting stents reduce this risk to less than 10 percent, and less than 5 percent of people need repeat procedures.

Millions of people with heart problems have been successfully treated with drug-eluting stents, preventing the need for more-invasive procedures such as coronary artery bypass surgery. The reduced risk of re-narrowing from drug-eluting stents minimizes the need for repeat hospitalization and repeat angioplasty procedures — each of which carry some risk of complications including heart attack and stroke.

Why is there some concern about using drug-eluting stents?

The Food and Drug Administration (FDA), which monitors the use of medical devices, considers both bare-metal and drug-eluting stents to be safe and effective in most people. But, all stents involve some risk. Sometimes the angioplasty procedure itself can cause complications such as a heart attack, blood clots, bleeding or injury to the blood vessels. Both bare-metal and drug-eluting stents have a risk of clotting both early and late after implantation.

It appears that in some people who get drug-eluting stents, there's a small increased risk of blood clots forming in the stent once the drug coating has been used up — sometimes a year or more after stent implantation. This risk is still quite low; about 0.5 percent or less when stents are used for FDA-approved reasons. The risk appears to be slightly higher when drug-eluting stents are used for off-label uses, ranging from about 0.4 to 1.6 percent.

Do drug-eluting stents increase risk of heart attacks?

An FDA advisory panel found that when drug-eluting stents are used "on-label" — meaning for specific situations approved by the FDA — there was no increased risk of heart attack or death with drug-eluting stents compared with bare-metal stents. However, about 60 percent of the time stents are used for "off-label" indications — meaning for reasons that, while appropriate, are not specifically spelled out in the FDA guidelines. When stents are used off-label, it's generally for more-complex cases, such as in someone who has multiple blockages and other complications.

The FDA panel said when drug-eluting stents are used off-label, there's a small but increased risk of blood clotting that can lead to heart attack and death. But, it's unknown if drug-eluting stents cause this increased risk or whether people in this group tend to be at higher risk in the first place.

There are a variety of potential explanations for blood clots developing later after implantation. Much of it may have to do with how long a person takes anti-platelet medications — aspirin, clopidogrel (Plavix) — which help prevent blood clots from forming in the stents. If these medications are stopped earlier than recommended or an individual doesn't have an effective response to the anti-clotting medications, there can be problems. People also have varying healing times.

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HB00090

July 19, 2008

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