May 19, 2007 A study showing that diabetic patients who are treated with long-term anti-clotting therapy are less likely to have a heart attack or die more than a year after stenting has been named among the best research papers presented at the 30th Annual Scientific Sessions of the Society for Cardiovascular Angiography and Interventions (SCAI), May 9--12, 2007.
The study found that regardless of whether clogged coronary arteries were propped open with a drug-eluting or bare metal stent, diabetic patients were more likely to enjoy continued good health if treatment with the anti-clotting drug clopidogrel was continued for more than 6 months.
The new study suggests that physicians may need to tailor anti-clotting therapy to the special needs of patients with diabetes, a condition that not only causes high blood sugar levels but can damage and inflame arteries throughout the body.
"Diabetics are among the highest-risk groups undergoing coronary interventions," said Somjot S Brar, M.D., a cardiologist at Kaiser Permanente Medical Center in Los Angeles. "It is very common for these patients to have diffuse coronary artery disease."
In patients who do not have diabetes, cardiologists typically prescribe a combination of aspirin and clopidogrel for about 1 month after placement of a bare metal stent, to prevent blood clotting, or thrombosis, in the stent during healing. With drug-eluting stents, it is now common to extend the length of treatment with anti-clotting medication to a full year, based on evidence that these devices are more prone to very late thrombosis than was once believed. The ideal length of clopidogrel therapy remains unknown, however, particularly in patients with diabetes.
In the study presented during the SCAI Annual Scientific Sessions, Dr. Brar and his colleagues identified 671 diabetic patients who had a stenting procedure and remained healthy during the first 6 months of follow-up. Patients were then divided into 4 groups, depending on whether they had been treated with a bare metal or drug-eluting stent, and whether they were continuing to take clopidogrel for longer than 6 months.
One year later, diabetic patients who were treated with a drug-eluting stent were less likely to have suffered a heart attack or died if they continued taking clopidogrel than if they discontinued the medication (2.2 percent versus 5.5 percent, respectively; p=0.07). More surprising was the finding that even with bare metal stents, long-term clopidogrel therapy significantly reduced the risk of death or heart attack (3.5 percent versus 12.2 percent, p=0.01). Among patients who discontinued clopidogrel after 6 months, the difference in the combined rate of death or heart attack for drug-eluting and bare metal stents was not statistically significant.
Dr. Brar speculated that in diabetic patients, long-term clopidogrel therapy may be helpful regardless of the type of stent because it prevents blood clots from forming on inflamed plaques throughout the diseased coronary arteries, not just on the stent itself.
As for when it is safe to stop clopidogrel in diabetic patients, the study recorded the lowest rate of death or heart attack among those who continued therapy for up to 1 year. After that, the anti-clotting medication did not further reduce risk.
"Regardless of the type of stent, clopidogrel should be continued for more than 6 months--and perhaps for as long as 1 year--in diabetic patients, whenever possible," Dr. Brar said.
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