Benefit of Clopidogrel over Aspirin Is Amplified in Patients with a History of Ischemic Events

Background and Purpose-The goal of this study was to examine the influence of preexisting symptomatic atherosclerotic disease on subsequent ischemic event rates and compare the efficacy of clopidogrel versus aspirin (acetylsalicylic acid, ASA) in patients with such disease. Methods-Using the CAPRIE database, we performed multivariate analyses for patients who had symptomatic atherosclerotic disease (ischemic stroke [IS] or myocardial infarction [MI] in their medical history before enrollment in the Clopidogrel Versus Aspirin in Patients at Risk of Ischemic Events (CAPRIE) trial. Two composite end points were used: (1) IS, MI, or vascular death and (2) IS, MI, or rehospitalization for ischemia. Results-In the CAPRIE population, prior IS and MI each were statistically significant predictors of subsequent ischemic events. Compared with the overall population, patients with preexisting symptomatic atherosclerotic disease had elevated event rates for the end point of IS, MI, or vascular death; 3-year rates were 20.4% with clopidogrel and 23.8% with ASA (absolute risk reduction, 3.4%; 95% CI, -0.2 to 7.0; number needed to treat, 29; relative risk reduction, 14.9%; P=0.045). Similar results were obtained for the end point of IS, MI, or rehospitalization for ischemia; 3-year event rates were 32.7% with clopidogrel and 36.6% with ASA (absolute risk reduction, 3.9%; 95% CI, -0.4 to 8.1; number needed to treat, 26; relative risk reduction, 12. 0%; P=0.039). Conclusions-CAPRIE patients with a history of prior symptomatic atherosclerotic disease had a high rate of subsequent ischemic events. The absolute benefit of clopidogrel over ASA seemed to be amplified in such high-risk patients.