Stent thrombosis after drug-eluting stent implantation: incidence, timing, and relation to discontinuation of clopidogrel therapy over a 4-year period.

AIMS: To assess the incidence, timing, and relation of drug-eluting stent (DES) thrombosis to discontinuation of clopidogrel therapy. METHODS AND
RESULTS: This prospective observational cohort study included 6816 consecutive patients that underwent successful DES implantation. Primary endpoint was definite stent thrombosis (ST). During 4 years of follow-up, definite ST was observed in 73 patients, corresponding to a cumulative incidence of 1.2%. Cumulative incidence of ST at 30 days was 0.5 and 0.8% at 1 year, respectively. Discontinuation of clopidogrel therapy was significantly associated with ST only in the first 6 months after the procedure (P < 0.001). During that period, the median time interval from clopidogrel discontinuation to ST was 9 days [interquartile range (IQR) 5.5-22.5] while thereafter it was 104.3 days (IQR 7.4-294.8).
CONCLUSION: The 4 year incidence of ST after DES implantation is low. A relevant number of ST occur early after discontinuation of clopidogrel therapy. The dependence of ST on discontinuation of clopidogrel therapy seems to be mostly confined to the first 6 months after DES implantation. However, specifically designed randomized studies are required to establish the optimal length of clopidogrel therapy after DES implantation.