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In some patients with acute myocardial infarction (MI), the use of sirolimus (Rapamune, Wyeth)-eluting stents drastically reduced the rate of in-stent restenosis at one year, compared with uncoated, bare-metal stents, according to the results of a new study.
In a separate study, the use of paclitaxel-eluting stents in acute MI reduced the incidence of serious adverse cardiac events at one year as compared with uncoated stents. However, the difference was not statistically significant.
At one year following implantation of the sirolimus-eluting CYPHER stent (Cordis Corp.), patients had a target vessel failure rate of 7.3% versus 14.3% in the bare-metal stent patient population, according to the study.
"The new thing is to use DESs in acute situations in which patients are having MIs," said Cam Patterson, M.D., chief, division of cardiology and director of the Carolina Cardiovascular Biology Center, University of North Carolina, Chapel Hill.
Before this study, cardiologists believed there was a possibility that MI patients could actually do worse with a DES and opted for bare-metal stents. "The first important feature of both of these studies is that with paclitaxel and sirolimus, the MI patients don't do worse," said Patterson.
Restenosis, the renarrowing of a coronary artery after it has been treated with angioplasty or stenting, occurs during the healing process when scar tissue grows to the point where it can narrow the artery.
Greg Laine, Pharm.D., clinical coordinator in critical care at St. Luke's Episcopal Hospital in Houston, said that that once an epithelial cell lining is established over the stent, the risk of stent thrombosis decreases. The rationale for using DESs, he noted, is that they prevent neointimal overproliferation to the point where the vessel occludes. "Certainly, there does appear to be a lower restenosis rate with DESs," he said.
Despite the good news about DESs and a reduced rate of restenosis, the risk for stent thrombosis appears to persist for a longer period of time compared with bare-metal stents. That's why patients with DESs are prescribed a regimen of combined antiplatelet therapy-usually Plavix (clopidogrel, Bristol-Myers Squibb) plus aspirin in the short term and aspirin monotherapy in the long term. Laine noted that by taking a potent antiplatelet combination, restenosis can be attenuated.
"Plavix is essential in the short term," said Laine. Most patients with a DES are advised to take clopidogrel for at least six months, often up to one year or longer after their procedure.
But compliance is a problem with many patients, and so is the ability for some patients without insurance to pay for the drug. Patients who have stable coronary artery disease but have not had an MI are able to discuss the benefits of taking clopidogrel with their doctors before a stent is implanted. But with MI patients, that decision process doesn't necessarily take place. "That's the one issue that looms over the use of DESs in MI patients," said Patterson.
Laine said that patients with a financial issue should discuss it with their doctor. However, he warned that patients should not stop taking clopidogrel on their own.
Although physicians can feel reasonably comfortable using DESs in MI patients, these stents are not for everyone. Experts warn that DESs are safe when used to treat the types of cases for which the devices were approved. To that end, the Food & Drug Administration announced that it is planning to convene a panel by the end of the year to evaluate the risk of DESs and recommend any necessary label changes. The panel will also discuss the appropriate duration of therapy with antiplatelet agents.