Study Shows High Stent Thrombosis Rates in African Americans

August 30, 2010—The American Heart Association announced that a study published by Sara D. Collins, MD, et al online ahead of print in Circulation showed that African American race is a distinct risk factor for developing life-threatening blood clots after receiving a drug-coated stent. African American race was the strongest predictor of clotting that occurred more than 30 days after implantation, the investigators said.

For the study, investigators examined data on 7,236 patients who had drug-eluting stents implanted between mid-2003 and the end of 2008. Even after considering other known risk factors—such as diabetes, hypertension, and kidney problems—the investigators found that African Americans still experienced a higher rate of thrombosis or clotting.

“The bottom line is this is not just because this population is sicker or less compliant, but there is something else there that needs to be explored,” commented lead investigator Ron Waksman, MD. “Physicians and patients need to know that African Americans are at a higher risk of developing stent thrombosis, which is associated with heart attack or death.”

In the study, African American patients were nearly three times as likely to experience clotting as non-African American patients. Clotting rates for African Americans compared to non-African Americans were 1.71% versus 0.59% after 30 days, 2.25% versus 0.79% at 1 year, 2.78% versus 1.09% at 2 years, and 3.67% versus 1.25% at 3 years. The rate of death from all causes at 3 years was also higher among African Americans (24.9% versus 13.1% in other races).

In the study, African Americans had increased rates of stent thrombosis even though they took clopidogrel after the procedure as prescribed at a higher rate than other races.

Dr. Waksman stated that further studies are needed to determine what should be done to reduce the blood-clotting risks in African Americans, and that more African American participants are needed in key clinical trials to determine if the treatment works before a drug is on the market. “We are committed to further exploring these disparities and how African Americans can benefit from drug-eluting stents without increasing the risk of stent thrombosis,” added Dr. Waksman.

According to the American Heart Association, possible genetic differences in the way African Americans' bodies react to the anti-clotting medication clopidogrel may have an impact. In some studies, investigators found that this genetic difference occurs more often in African Americans than in white patients. Blood tests or genetic testing determine if someone is a “poor metabolizer” of clopidogrel.