Acute ST-Segment Elevation Myocardial Infarction (STEMI)

Acute coronary syndrome (ACS) encompasses conditions characterized by a sudden decrease in myocardial perfusion, presenting as ST-segment elevation myocardial infarction (STEMI), non–ST-segment elevation myocardial infarction (NSTEMI), or unstable angina. Globally, over 7 million individuals are diagnosed with ACS annually, with more than 1 million cases requiring hospitalization in the United States each year. STEMI results from the complete blockage of a coronary artery and represents about 30% of all ACS cases. An acute STEMI is marked by transmural myocardial ischemia resulting in myocardial injury or necrosis. The current 2018 clinical definition of myocardial infarction requires confirming the presence of ischemic myocardial injury with abnormal cardiac biomarker levels. STEMI is a clinical syndrome involving myocardial ischemia, electrocardiography (ECG) changes, and chest pain (see Image. Electrocardiogram Tracing for a Case of Proximal Left Anterior Descending Occlusion).

If electrocardiography indicates STEMI, prompt reperfusion through primary percutaneous coronary intervention (PCI) within 120 minutes can lower mortality from 9% to 7% (see Image. ST-segment Elevation Myocardial Infarction on Electrocardiogram). In cases where PCI within this timeframe is not feasible, full-dose fibrinolytic therapy with alteplase, reteplase, or tenecteplase should be administered to patients younger than 75 and without contraindications to medical intervention. Individuals 75 and older should receive half the normal dose of fibrinolytic therapy. Alternatively, full-dose streptokinase may be considered when cost is a concern. Following fibrinolytic treatment, patients should be transferred to a facility capable of performing PCI within the next 24 hours.