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Impaired responses to antiplatelet therapy assessed by laboratory tests are associated with an increased risk of recurrent ischemic events after percutaneous coronary intervention (PCI). This study was designed to determine the relation between responses to aspirin and clopidogrel as assessed by a point-of-care assay (Verify Now, Accumetrics, San Diego, California) and periprocedural myocardial infarction (PMI) in patients undergoing elective PCI for stable angina. One hundred twenty-two consecutive patients undergoing elective coronary stenting prospectively received aspirin 500 mg and clopidogrel 600 mg ≥12 hours before PCI. Clopidogrel response was measured with P2Y12 reaction units (PRUs) and percent inhibition P2Y12 from baseline (percent inhibition P2Y12) and aspirin response with aspirin reaction units (ARUs). Troponin T level was considered positive if it was >0.03 ng/ml. Responses to aspirin and clopidogrel were correlated (r = 0.42, p <0.0001). PMI occurred in 27 patients (22%) who showed significantly lower percent inhibition P2Y12 (25.3 ± 26 vs 38.3 ± 25, p = 0.01) and a trend toward higher PRU values (221 ± 87 vs 193 ± 94, p = 0.21). We did not find any difference for aspirin response as assessed by ARUs in patients with or without PMI (460 ± 82 vs 454 ± 73, p = 0.82). Stratification of percent inhibition P2Y12 isolated a quartile of clopidogrel nonresponders (inhibition P2Y12 <15%) with significantly higher incidence of PMI (44% vs 15%, odds ratio 4.6, 95% confidence interval 1.9 to 11.5, p = 0.001). In conclusion, point-of-care assessment of clopidogrel response reliably predicted PMI after low- to medium-risk elective PCI for stable angina. © 2008 Elsevier Inc. All rights reserved.
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