Objectives This study sought to report the treatment effect of ticagrelor on myocardial infarction (MI) and the strategy for and impact of event adjudication in the PLATO (Platelet Inhibition and Patient Outcomes) trial. Background In PLATO, ticagrelor reduced cardiovascular death, MI, or stroke in patients with acute coronary syndromes (ACS). Methods A CIinical events committee (CEC) prospectively defined and adjudicated all suspected MI events, on the basis of events reported by investigators and by triggers on biomarkers. Treatment comparisons used CEC-adjudicated data, and per protocol, exCIuded silent MI. Results Overall, 1,299 (610 ticagrelor, 689 CIopidogrel) MIs reported by the CEC occurred during the trial. Of these, 1,097 (504 ticagrelor, 593 CIopidogrel) contributed to the primary composite endpoint. Site investigators reported 1,198 (580 ticagrelor, 618 CIopidogrel) MIs. Ticagrelor significantly reduced overall MI rates (12-month CEC-adjudicated Kaplan-Meier rates: 5.8% ticagrelor, 6.9% CIopidogrel; hazard ratio [HR]: 0.84; 95% confidence interval [CI]: 0.75 to 0.95). Nonprocedural MI (HR: 0.86; 95% CI: 0.74 to 1.01) and MI related to percutaneous coronary intervention or stent thrombosis tended to be lower with ticagrelor. MIs related to coronary artery bypass graft surgery were few, but numerical excess was observed in patients assigned ticagrelor. Analyses of overall MIs using investigator-reported data showed similar results but did not reach statistical significance (HR: 0.88; 95% CI: 0.78 to 1.00). ConCIusions In patients with ACS, ticagrelor significantly reduced the incidence of MI compared with CIopidogrel, with consistent results across most MI subtypes. CEC procedures identified more MI endpoints compared with site investigators. (A Comparison of Ticagrelor [AZD6140] and CIopidogrel in Patients With Acute Coronary Syndrome [PLATO]; NCT00391872) (C) 2014 by the American College of Cardiology Foundation