Acute Coronary Syndrome: Presentation and Diagnostic Evaluation.

Acute coronary syndrome (ACS) is an acute myocardial infarction (MI) or ischemia, usually from acutely disrupted coronary artery blood flow. Patients commonly present to the emergency department (ED) with chest pain or pressure but sometimes have atypical symptoms. Evaluation begins with an electrocardiogram (ECG) obtained within 10 minutes of presentation. If ST-segment elevation is present, ST-segment elevation MI (STEMI) is diagnosed. If STEMI is not present, troponin levels should be measured using one of several recommended protocols. Troponin levels greater than 99th percentile of the upper reference limit are consistent with ACS. If the ECG finding is normal and results of two troponin tests are negative, risk stratification should be calculated using Thrombosis in Myocardial Infarction (TIMI) or HEART (History, ECG, Age, Risk factors, initial Troponin) score. Based on the score, further evaluation to exclude coronary artery disease (CAD) is completed during hospitalization or after discharge, using exercise treadmill testing, stress echocardiography, myocardial perfusion scintigraphy, or coronary computed tomography angiography. Although ACS is less likely in outpatients, CAD must still be considered. Many patients with ACS are misdiagnosed. Between 2% and 5% of patients are inappropriately discharged from the ED.