ARTEMIS is a prospective, cluster-randomized clinical trial that will evaluate whether patient copayment elimination significantly influences antiplatelet therapy selection and long-term adherence, as well as patient outcomes and overall cost of care after acute myocardial infarction. Approximately 11,000 patients with ST-elevation myocardial infarction (STEMI) or non-STEMI (NSTEMI) will be enrolled at the approximately 300 hospitals in this study. Study sites selected for ARTEMIS will be geographically diverse, and will represent a diversity of hospital types and capabilities (e.g., teaching hospital, community hospital, etc). After institutional review board (IRB) approval of the study, each hospital will be randomized into either the intervention arm or the control arm. Hospitals randomized to the intervention arm will have the opportunity to offer enrolled patients either clopidogrel (generic P2Y12 receptor inhibitor option) or ticagrelor (brand P2Y12 receptor inhibitor option) without patient contribution to copayment in the next 12 months after the index MI discharge. Hospitals in the control arm will provide care per usual clinical routine. Notably, for both intervention and control arms, all patient management decisions (including the choice of antiplatelet therapy) are completely at the discretion of the care providers. Duration of antiplatelet therapy will also be at the discretion of care providers. All enrolled patients will be followed up to 15 months after index MI discharge to collect data on longitudinal treatment patterns and outcomes. Primary and secondary endpoints will be assessed at 12 months. An additional three months of follow up will assess for antiplatelet persistence and clinical events after discontinuation of the copayment intervention. Centralized follow-up will be conducted every 3 months via telephone or web-based contact.