Chest pain accounts for approximately six million annual visits to emergency departments (ED) in the United States (US), making it the second most common ED complaint . Patients present with a spectrum of signs and symptoms reflecting the many potential etiologies of chest pain. Diseases of the heart, aorta, lungs, esophagus, stomach, mediastinum, pleura, and abdominal viscera may all cause chest discomfort.
One of the most common causes of chest pain in patients who present for evaluation is acute coronary syndrome, accounting for approximately 12 to 15 percent of all cases of chest pain in the emergency department setting. The term “acute coronary syndrome” (ACS) is applied to patients in whom there is evidence of myocardial ischemia or infarction. (See 'Criteria for diagnosis' below.)
This topic discusses the evaluation of patients with chest pain at low or intermediate risk for ACS as assessed by the results of the initial history, physical exam, electrocardiogram (ECG), and initial biomarkers. The approach to other patients with chest pain or to those with a high likelihood of ACS is found elsewhere. (See "Evaluation of the adult with chest pain in the emergency department" and "Initial evaluation and management of suspected acute coronary syndrome in the emergency department".)
CRITERIA FOR DIAGNOSIS
The term “acute coronary syndrome” (ACS) is applied to patients in whom there is evidence of myocardial ischemia or infarction. There are three types of ACS: ST elevation (formerly Q wave) myocardial infarction (STEMI); non-ST elevation (formerly non-Q wave) MI (NSTEMI); and unstable angina (UA). The first two are characterized by a typical rise and/or fall in biomarkers of myocyte injury . UA is characterized by myocardial ischemia without elevated biomarkers and is often a clinical diagnosis based on history, dynamic electrocardiogram (ECG) changes, or inducible ischemia on stress testing. Establishing whether a patient has ACS requires integration of information obtained from a careful patient interview and examination as well as from serial evaluation of the ECG, troponin levels, and occasionally provocative testing results. (See "Criteria for the diagnosis of acute myocardial infarction", section on 'Third Universal Definition of MI'.)
GOALS OF EVALUATION
The primary focus in the evaluation of patients for acute coronary syndrome (ACS) is to reasonably confirm or exclude in an expeditious manner ACS as a cause for the patient's symptoms. Reasonable confirmation of ACS is generally secured by the finding of an elevated troponin, diagnostic electrocardiogram (ECG) changes, or abnormal provocative testing. ACS is reasonably excluded when the probability of ACS is below a 1 to 2 percent threshold [3,4].