Acute Coronary Syndrome: Diagnostic Evaluation.

Myocardial infarction (MI), a subset of acute coronary syndrome, is damage to the cardiac muscle as evidenced by elevated cardiac troponin levels in the setting of acute ischemia. Coronary artery disease is the leading cause of mortality in the United States. Chest pain is a common presentation in patients with MI; however, there are multiple noncardiac causes of chest pain, and the diagnosis cannot always be made based on initial presentation. The assessment of a possible MI includes evaluation of risk factors and presenting signs and symptoms, rapid electrocardiography, and serum cardiac troponin measurements. A validated risk score, such as the Thrombolysis in Myocardial Infarction score, may also be useful. Electrocardiography should be performed within 10 minutes of presentation. ST elevation MI is diagnosed with ST segment elevation in two contiguous leads on electrocardiography. In the absence of ST segment elevation, non-ST elevation ACS can be diagnosed. An elevated cardiac troponin level is required for diagnosis, and an increase or decrease of at least 20% is consistent with MI. In some patients with negative electrocardiography findings and normal cardiac biomarkers, additional testing may further reduce the likelihood of coronary artery disease. Cardiac catheterization is the standard method for diagnosing coronary artery disease, but exercise treadmill testing, a stress myocardial perfusion study, stress echocardiography, and computed tomography are noninvasive alternatives.