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Studies Highlight Pitfalls of Drug-Coated Stents

For example, many patients don't take drugs that can ward off dangerous clots

MONDAY, March 26, 2007 (HealthDay News) -- About a third of patients who receive artery-opening drug-coated stents aren't taking the anticlotting drug doctors often prescribe to keep the stent functioning as it should, a new U.S. study finds.

Other patients simply don't respond to Plavix, so they remain at high risk of dangerous clots, a second study found.

Trials such as these, testing the "real-world" effectiveness of drug-coated (or "eluting") stents, were presented Monday at the American College of Cardiology's annual meeting, in New Orleans. Drugs impregnated in the stent -- a tiny mesh tube used to keep arteries open -- are released over time to fight artery reclosure, a process known as restenosis. Drug-coated stents typically cost upwards of $2,000 each.

In his team's study, Dr. George Dangas, program director of interventional cardiology at Columbia University Medical Center, New York City and colleagues used data from the MATRIX Registry, which includes more than 1,500 patients treated with drug-coated stents.

"Complex patients come with complex lesions," Dangas noted in a prepared statement. "The only way to test drug-eluting stents as physicians really use them is to include an unselected population, just as you would find in the community," he added.

At one year, 1.7 percent of the patients who had received a drug-coated stent died. Death from heart disease was 0.8 percent, while the rate of heart attack was found to be 3.1 percent. In addition, 7.3 percent of patients underwent a subsequent procedure to reopen the stented artery. Also, 0.4 percent of patients developed a clot in or around the stent, and 0.3 percent developed a probable stent clot.

The total one-year rate of "major adverse cardiac events" was almost 11 percent, the researchers report.

To prevent stent thrombosis (clotting), patients in the registry were counseled to continue using the drug Plavix, which helps prevent clots. However, "we found that about one-third of patients were not taking Plavix at one year," Dangas said.

In a second study, Dr. David Antoniucci, the head of cardiology at Careggi Hospital, Florence, Italy, and colleagues found that patients who do not respond to medications such as Plavix had three times the risk of developing a stent-linked clot compared with patients who are responsive to the drug.

The study included more than 800 patients, all of who receive a drug-coated stent and were then prescribed Plavix as well as aspirin for six months. The Italian team report that 8.6 percent of people who did not seem to respond to the drug experienced a clot, compared with 2.3 percent of those who did respond to the medication.

These findings suggest that adherence to anti-clotting therapy may not protect everyone against stent-linked clots, the researchers reported. In a prepared statement, Antoniucci said that his team's trial, "is the first prospective clinical trial that has shown an increased risk of thrombosis in drug-eluting stents in patients who are non-responders to clopidogrel (Plavix)."

Testing patients for responsiveness to Plavix before stenting might influence treatment. "Non-responders might need alternative antiplatelet drugs or different dosages, or perhaps they should be treated with bare-metal [non-drug-coated] stents or offered the opportunity for coronary bypass surgery," he said.

In a third study, Dr. Julinda Mehilli, of Deutsches Herzzentrum, Munich, Germany, and colleagues tested the hypothesis that a form of estrogen called estradiol might improve the release of the drug rapamycin from the surface of a stent. Estradiol has been shown to promote healing after implanting stents in animals.

However, the trial found that adding estradiol to the drug-coated stent "is not associated with any measurable benefit during the first year after angioplasty," Mehilli said in a prepared statement.

Among 500 patients, Mehilli's group found no significant differences between the patients who received an estradiol-plus-rapamycin-eluting stent and patients who received a stent coated with rapamycin alone.

The incidence of artery reclosure was 17.6 percent among those given estradiol and 16.9 percent among those not given estradiol. For death and heart attack, the incidence was 7.9 among patients receiving estradiol and 8.0 percent among those not receiving estradiol. The incidence of stent thrombosis was 0.8 percent and 1.2 percent, respectively, the authors said.

More information

For more information on stents, visit the American Heart Association.

SOURCES: March 26, 2007, American College of Cardiology meeting, New Orleans
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