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There's a dark side to drug-coated stents
Drugs in the devices keep arteries from reclogging after balloon angioplasty -- a big problem with earlier, bare-metal stents. Introduced just three years ago, drug-coated, or drug-eluting, stents became all the rage among cardiologists.
But in rare cases, they seem to cause sudden cardiac death or severe heart attack a year or more after they're implanted.
Concern heightened with reports at last September's meeting of the World Congress of Cardiology in Barcelona, Spain. Despite reassurances that the risks are small, data presented at an October meeting of heart specialists in Washington, D.C., confirms there is a problem.
"There is a possible dark side to drug-eluting stents," Deepak L. Bhatt, MD, associate director of The Cleveland Clinic's heart center, tells WebMD. "The risk has been exaggerated -- but there is something there. People are not dropping in droves due to drug-eluting stents, but you can't say there is no cause for concern."
"It is a real concern," agrees Richard Milani, MD, head of preventive cardiology at New Orleans' Ochsner Clinic. "There are more questions than we have answers. We don't know how often this really happens. We don't really know who the people most at risk are," he tells WebMD.
How great is the risk? The data aren't in yet.
But in an analysis of clinical-trial data, Bhatt and colleagues found that over the course of a couple of years, patients who get drug-coated stents have 0.5% more risk of dangerous blood clots than those who get bare-metal stents.
"The absolute risk to an individual patient is less than one in 200," Bhatt says. But "with a million stents going in each year in the U.S. and twice that number worldwide, this is not trivial."
2 Steps Forward, 1 Step Back
For a person with a blocked artery, doctors have two basic treatments. One is bypass surgery -- taking a blood vessel from somewhere else in the body and using it to bypass the blockage.
The other solution is to insert a catheter into the artery, inflate a balloon that reopens the blockage, and place a stent (or wire-mesh cylinder) in the blood vessel to hold it open while it heals.
As the artery heals, new cells grow over the inside of the stent, essentially making it part of the blood vessel.
Unfortunately, the body tends to see the stent as a foreign object. Sometimes, scar tissue forms inside the stent, once again blocking the artery.
New drug-eluting stents are coated with a polymer that slowly releases a powerful drug. This drug keeps scar tissue from forming.
Unfortunately, it also slows the healing process. That's a problem -- because until the blood vessel heals inside of the stent, there's a risk of deadly blood clots.
The Benefits
Stents have revolutionized the treatment of blocked arteries. They've vastly reduced the need for bypass surgery.
And the new drug-eluting stents have greatly decreased the risk of stent blockage. The newly identified risk does not outweigh the overall benefit of the new stents.
Johnson & Johnson subsidiary Cordis Corp. and Boston Scientific make the two drug-eluting stents that now have FDA approval.
Boston Scientific did not respond to WebMD's interview request.
Cordis spokeswoman Mariela Melendez notes that patients who get bare-metal stents also may rarely suffer sudden cardiac death and heart attacks.
"At the end of the day, we believe this is a rare event," Melendez tells WebMD. "It is a significant challenge that we take very seriously. We want to get to the bottom of this. But at this point, we don't see much difference between bare-metal stents and drug-coated stents."
Most of the blood clots that lead to death or heart attackheart attack happen when patients stop taking anticlotting drugs.
Currently, combination treatment with Plavix and aspirin is recommended for all patients for the first year. Patients who can tolerate this treatment even longer may be able to avoid the additional risk.
"In the end, it is a wash with respect to the risk of death or heart attack," Bhatt says. "For the right patient, a drug-eluting stent is the best option. But for the wrong patient, someone that has a bleeding problem or a recurrent gastrointestinal bleeding issue such as diverticulitisdiverticulitis, the drug-eluting strategy may not be so great for them. Because keeping them on aspirin and Plavix for a long while would be a bad thing."
Bottom Line for Patients
What does all this mean for the millions of people with drug-coated stents in their bodies? Medical journalist Miriam Shuchman, MD, reviewed the stent issue for the Nov. 9 issue of The New England Journal of Medicine.
"It is true the risk for any given patient is small -- but patients need to talk with their doctors," Shuchman tells WebMD.
"They will be hearing they need to stay on their Plavix and aspirin for longer than they initially thought," he says.
"Where this does not lead is to a situation where patients must say, 'Take it out.' The level of risk is not such that you would do that," Shuchman says. "I did not hear any doctor say that was indicated."
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作者:admin@医学,生命科学 2010-10-02 19:08
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