Clopidogrel use and clinical events after drug-eluting stent implantation: Findings from the HealthCore Integrated Research Database

Background: Relationships between long-term use and level of dual antiplatelet therapy and outcomes after drug-eluting stent implantation are not well established. Methods: This is a retrospective cohort study of 9,256 patients receiving drug-eluting stents between January 2003 and August 2006. We classified patients according to tertiles of clopidogrel use during the 12 months after stent implantation. We used inverse probability weighting to account for differential selection into levels of clopidogrel use and logistic regression to estimate propensity scores for levels of clopidogrel use. We used Cox proportional hazards models to estimate effects of level of clopidogrel use on risk of bleeding events, death, and death or nonfatal myocardial infarction. Results: There were 3,102 patients in the high-use group, 3,069 in the medium-use group, and 3,085 in the low-use group. Compared with the high-use group, risk of death or nonfatal myocardial infarction was greater in the medium-use group (hazard ratio [HR] 1.46, 95% CI 1.09-1.99, P = .01) and the low-use group (HR 1.59, 95% CI 1.18-2.14, P = .002). The risk of bleeding events was lower in the medium-use group (HR 0.84, 95% CI 0.71-0.98, P = .03) and the low-use group (HR 0.77, 95% CI 0.65-0.90, P = .002). Conclusions: Higher clopidogrel use 12 months after drug-eluting stent implantation was associated with a greater risk of subsequent bleeding events. Lower use was associated with a greater risk of death or nonfatal myocardial infarction.