Background: Platelet reactivity is enhanced in patients with acute STEMI. The clinical impact of high residual platelet reactivity (HPR) during clopidogrel therapy assessed by a point-of-care assay is unknown in patients with STEMI undergoing primary PCI. Methods: We used the VerifyNow P2Y12 assay to seek clinical impact of predischarge platelet reactivity in 158 patients with STEMI receiving dual-antiplatelet therapy who underwent primary PCI with DES. All patients received a single 600 mg clopidogrel and a 300 mg aspirin loading dose followed by a 75 mg clopidogrel and a 200mg aspirin daily maintenance dose. We sought cardiovascular death, nonfatal MI, and target vessel revascularization at a 12-month follow-up. Results: The optimal cutoff value in predicting 12-month cardiovascular death and nonfatal MI was P2Y12 reaction unit (PRU) ��� 280 (area under curve 0.68, 95% CI 0.54-0.83, p=0.02, sensitivity 66.7%, specificity 68.5%) by receiver operating curve. On univariate Cox regression analysis, HPR defined as PRU above 280 was associated with a significantly higher risk of cardiovascular death or nonfatal MI (18.6% vs. 5.1%, HR 3.92, 95% CI 1.26-11.29, p=0.011). Nonfatal MI (6.8% vs. 1.0%, p=0.072) and cardiovascular death (10.2% vs. 4.0%, p=0.136) tended to be higher in HPR group compared with no HPR group. Stent thrombosis was not different between the two group (5.1% vs. 3.0%, p=0.460). HPR (HR 3.29, 95% CI 1.03-10.54, p=0.045) and elderly patient above 80 years old (HR: 8.86, 95% CI 1.45-54.04, p=0.018) was found to be a significant and independent predictor of cardiovascular death or nonfatal MI on multivariate analysis. The cardiovascular death or MI free survival was significantly lower in HPR group compared with no HPR group (log-rank test p=0.006) (Figure). Conclusion: Predischarge high HPR (PRU ���280) assessed by a point-of-care assay was able to predict a 12-month cardiovascular death or nonfatal MI in patients with STEMI receiving dual-antiplatelet therapy who underwent primary PCI with DES