Clinical significance of platelet reactivity during prasugrel therapy in patients with acute myocardial infarction

Abstract Background Although some studies have examined platelet reactivity (PR) during prasugrel treatment, little is known about PR during the early treatment period and its clinical significance in Japan. Methods We investigated the early and medium-term efficacy and safety of prasugrel in patients with acute myocardial infarction (AMI) undergoing primary percutaneous coronary intervention (PCI). Seventy-eight patients were enrolled and PR was measured (in P2Y 12 reaction units; PRU) by the VerifyNow P2Y 12 assay (Accumetrics, San Diego, CA, USA). Results In 44 patients, serial measurement revealed that PR was significantly higher at 2 h after administration of the 20-mg loading dose of prasugrel than on the morning of the second day at 17.6 ± 6.6 h after administration (191.6 ± 75.5 vs. 138.5 ± 68.9 PRU). During the 8-month follow-up period, bleeding events occurred in 18 patients (23.1%) (GUSTO minor: 15 patients). Multivariate regression analysis identified oral anticoagulant use as a significant predictor of bleeding events during admission [odds ratio (OR): 4.214, 95% confidence interval (CI): 1.005–17.669, p  = 0.049]. Administration of prasugrel via a nasogastric tube was a significant predictor of high on-treatment platelet reactivity (HTPR) (PRU ≥ 230) (OR: 43.100, 95% CI: 4.517–411.251, p  = 0.001). In addition, HTPR was a significant predictor of major adverse cardiac events (cardiovascular death, non-fatal myocardial infarction, stent thrombosis, stroke, and sustained ventricular tachycardia) during the 8-month follow-up period (OR: 4.911, 95% CI: 1.164–20.722, p  = 0.030). Conclusions It is feasible to treat AMI patients with prasugrel. HTPR is a significant independent risk factor for adverse events in AMI patients receiving prasugrel after primary PCI.