Objectives: This study sought to determine the incidence of aspirin nonresponsiveness in addition to clopidogrel nonresponsiveness and whether this association identifies patients at an increased risk of drug-eluting stent (DES) thrombosis.
Background: Nonresponsiveness to clopidogrel is a predictor of DES thrombosis. No prospective data exist about the possible association of dual nonresponsiveness to clopidogrel and aspirin with DES thrombosis.
Methods: Platelet function was assessed after a loading dose of 600 mg clopidogrel in 746 patients who had successful DES implantation followed by 6-month dual-antiplatelet therapy. Platelet reactivity was assessed by light transmittance aggregometry using adenosine 5'-diphosphate, arachidonic acid, and collagen. The primary end point was definite/probable DES thrombosis at 6 months. The secondary end point was the composite of cardiac mortality and DES thrombosis.
Results: The incidence of dual nonresponsiveness to aspirin and clopidogrel was 6%. Definite/probable DES thrombosis was significantly higher in dual aspirin and clopidogrel nonresponders (11.1%) than in clopidogrel and aspirin responders (2.1%, p < 0.001), isolated clopidogrel nonresponders (2.2%, p < 0.05), or aspirin nonresponders (2.3%, p < 0.05). The incidence of the secondary end point was 4.4% in isolated clopidogrel nonresponders, 2.3% in isolated aspirin nonresponders, and 13.3% in dual aspirin and clopidogrel nonresponders. Dual clopidogrel and aspirin nonresponsiveness was an independent predictor of DES thrombosis (hazard ratio: 3.18, 95% confidence interval: 1.14 to 8.83, p = 0.027) and the composite of cardiac mortality and DES thrombosis (hazard ratio: 2.94, 95% confidence interval: 1.16 to 7.41, p = 0.022).
Conclusions: Dual nonresponsiveness to aspirin and clopidogrel is a relatively infrequent condition that identifies patients at a very high risk of DES thrombosis or death.