In combination with low-dose ASA for patients with: - Non-ST elevation acute coronary syndrome (ACS)* (unstable angina or myocardial infarction [MI]); OR - ST-segment elevation myocardial infarction (STEMI); OR - Stent thrombosis while taking clopidogrel plus low-dose ASA. Treatment must be initiated in hospital. Notes: A) *ACS without ST elevation is defined as 2 of 3 of the following criteria: 1. ST-segment changes on electrocardiogram (ECG) indicating ischemia 2. Positive biomarker indicating myocardial necrosis 3. One of the following: - Greater than or equal to 60 years of age - Previous MI or coronary artery bypass graft (CABG) - Coronary artery disease (CAD) with greater than or equal to 50% stenosis in greater than or equal to 2 vessels - Previous ischemic stroke, transient ischemic attack (TIA; hospital-based diagnosis), carotid stenosis (greater than or equal to 50%), or cerebral revascularization - Diabetes mellitus - Peripheral artery disease - Chronic renal dysfunction B) Co-administration of ticagrelor with high maintenance dose ASA (greater than 150mg daily) is not recommended. C) Definite stent thrombosis, according to the Academic Research Consortium, is a total occlusion originating in or within 5 mm of the stent, or is a visible thrombus within the stent, or is within 5 mm of the stent in the presence of an acute ischemic clinical syndrome within 48 hours. Definite stent thrombosis must be confirmed by angiography or by pathologic confirmation of acute thrombosis. D) Ticagrelor is contraindicated in patients with active pathological bleeding, in those with a history of intracranial hemorrhage and moderate to severe hepatic impairment.