Patients presenting to the Emergency Department (ED) with ST-segment elevation acute myocardial infarction (STEMI) require rapid diagnosis and treatment to optimize their outcome. Early diagnosis is accomplished by acquiring a 12-lead electrocardiogram within 10 minutes after ED presentation to identify STEMI and then begin treatment. Most irreversible myocardial damage occurs within the first 3 hours after symptom onset so delivery of fibrinolytic therapy or mechanical opening of the coronary artery using percutaneous coronary intervention (PCI) must be initiated early after presentation to the hospital to achieve greatest benefit.