Personalization of Long-Term Antiplatelet Therapy - RAPID EXTEND

Inclusion Criteria: * \>50 years old at 1-year after myocardial infarction (non-ST-elevation myocardial infarction (NSTEMI) or ST-elevation myocardial infarction (STEMI)) during which they had percutaneous coronary intervention (PCI) * Compliant with dual antiplatelet therapy (DAPT) for ≥ 1 year without an ischemic or bleeding complication after PCI * Still on DAPT regimen at enrollment * Patients must have 1 of the following atherothrombotic risk enrichment criteria: i) Age≥ 65 years ii) Diabetes iii) 2nd Prior MI (\>1 year ago) iv) multi-vessel coronary disease v) creatinine clearance (CrCl) \<60 mL/min. Exclusion Criteria: * Intolerance to ticagrelor or clopidogrel * \>18 months post percutaneous coronary intervention (PCI) and myocardial infarction (MI) * Requirement of a P2Y12 inhibitor * Requirement of oral anticoagulation * Take concurrent CYP3A inducing drugs which may interact with ticagrelor (e.g. anti-epileptic drugs) * History of stroke, TIA or intracranial bleed * Recent GI bleed or major surgery * Life expectancy of \< 1 year * Platelet count \< 100,000/μl * Bleeding diathesis * On dialysis * Severe liver disease * At risk for bradycardia.