In this nationwide, registry-based study of patients with a history of AF admitted with a first-time MI treated with PCI and who filled a prescription for a P2Y12 inhibitor after discharge, we found that treatment with ticagrelor or prasugrel was associated with a reduced risk of MACE, without a concomitantly increased risk of bleeding when compared with clopidogrel. The gene discussed is P2RY12; the disease is atrial fibrillation.