Inclusion Criteria:  Written informed consent Age ≥ 18 years Atrial fibrillation requiring oral anticoagulation STEMI or NSTEMI (biomarker positive acute coronary syndrome) and successful completion of PCI (randomization will take place within 24h after successful PCI)  Exclusion Criteria:  Chronic renal insufficiency with glomerular filtration rate < 15 ml/min/1.73m2 Previous haemorrhagic stroke Contraindication for P2Y12-inhibitor Indication for oral anticoagulation with Vitamin K antagonists Moderate to severe mitral stenosis or mechanical heart valve Any bleeding BARC type ≥ 2 within the last 4 weeks before index procedure Pregnancy or lactation Inability to cooperate with the protocol requirements Life expectancy < 6 months Participation in another investigational drug study Previous enrolment in this study For women of childbearing potential no negative pregnancy test and no agree to use a reliable method of birth control during the study Previous treatment with GP IIb/IIIa inhibitors within the last 12 hours A known genetic disorder involved in the metabolism of the study medication