The Significance of Clopidogrel Low-Responsiveness on Stent Thrombosis and Cardiac Death Assessed by the Verifynow P2Y12 Assay in Patients With Acute Coronary Syndrome Within 6 Months After Drug-Eluting Stent Implantation

BACKGROUND AND OBJECTIVES Clopidogrel resistance or low-responsiveness may be associated with recurrent atherothrombotic events after drug-eluting stent (DES) implantation. We prospectively evaluated the association between clopidogrel resistance assessed by the Verifynow P(2)Y(12) assay (Accumetrics, San Diego, CA, USA) and stent thrombosis (ST) or cardiac death (CD) in patients with acute coronary syndrome (ACS) within 6 months after DES implantation. SUBJECTS AND METHODS We enrolled 237 consecutive patients (160 males, 65.2+/-10.3 years) with ACS who received a DES implantation. The composite endpoint was defined to CD or ST by Academic Research Consortium definitions within 6 months post-implantation. Clopidogrel resistance was defined as <20% inhibition of the P(2)Y(12) receptor. RESULTS Baseline demographic characteristics were similar between 142 normal individuals and 95 clopidogrel resistant patients. CD occurred in one case (0.7%) in the normal group and two cases (2.13%) in the resistant group (p=0.344). There was no episode of ST in the normal group and four episodes in the resistant group (4.2%, four definite ST) (p=0.035). Univariate logistic regression revealed an adjusted odds ratio (OR) for composite end point of CD or ST of 9.646 {95% confidence interval (CI) 1.139-81.679}, and multivariate logistic regression for composite end point revealed an OR of 12.074 (95% CI 1.205-120.992). CONCLUSION Clopidogrel low-responsiveness assessed by the Verifynow P(2)Y(12) assay is an independent predictor of ST and composite end point of ST or CD in patients with ACS within 6 months after DES implantation.