Posttreatment platelet reactivity on clopidogrel is associated with the risk of adverse events after off-pump coronary artery bypass

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Dual antiplatelet therapy with aspirin and clopidogrel is currently recommended in off-pump coronary artery bypass (OPCAB). However, no data exist concerning platelet reactivity on clopidogrel after OPCAB. The aim of this study was to assess the relationship between platelet reactivity and late major adverse cardiovascular events (MACEs) after OPCAB. In this prospective, single-center, observational study, on-clopidogrel platelet reactivity was measured using a point-of-care assay (VerifyNow system; Accumetrics Inc, San Diego, CA) in 859 patients who underwent OPCAB with 1 or more vein grafts. The primary end point was late MACEs (30 days-1 year) including cardiac death, nonfatal myocardial infarction, and target vessel revascularization. Receiver operating characteristic curve analysis was used to estimate the cutoff value of P2Y12 reaction units (PRUs) for MACEs. The optimal cutoff value for posttreatment reactivity for the incidence of late MACEs was ≥188 PRU (area under the curve 0.72, 95% CI 0.68-0.75, P = .002). The incidence of late MACEs was significantly higher in the high platelet reactivity (HPR; ≥188 PRU) group than in the low platelet reactivity (<188 PRU) group (3.6% vs. 1.4%, P = .040). Kaplan-Meier analysis revealed 1-year MACE-free survival rates of 98.4% ± 0.5% and 95.9% ± 1.3% in the low platelet reactivity and HPR groups, respectively (P = .034). According to a Cox regression hazard model, HPR was an independent risk factor for late MACE-free survival (hazard ratio 3.51, 95% CI 1.27-9.69, P = .015). High residual platelet reactivity after clopidogrel administration is strongly associated with 1-year MACE-free survival. Routine measurement of platelet reactivity and thorough monitoring of patients with HPR after OPCAB are warranted.