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™ P₂Y 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 P₂Y₁₂ 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™ P₂Y₁₂ 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.