Evaluation of Chest Pain in the Emergency Department
Sachin S. Goel
Samir R. Kapadia
I. INTRODUCTION.
Chest pain is one of the most common problems evaluated in the emergency department (ED).
A. Each year, approximately 5 million persons who arrive at an ED with chest pain are admitted to the hospital, mainly to an intensive care unit; 1.2 million of these patients are ultimately diagnosed with acute myocardial infarction (AMI). However, 2% to 4% of persons who arrive with chest discomfort and AMI are inappropriately discharged to home. This error in diagnosing myocardial infarction (MI) is dangerous and costly. Early recognition and treatment are also important because time to treatment is the single most important factor in the management of ST-elevation MI.
B. Rapid evaluation and risk stratification of patients with chest pain are essential to identify life-threatening conditions and improve outcomes. Emergency treatment is initiated in the ED to minimize permanent myocardial damage and improve survival, especially in patients with MI. The goal of treatment in ST-elevation MI is to achieve reperfusion as soon as possible, either by primary percutaneous coronary intervention or by thrombolytic therapy. Conversely, in patients with non—ST-elevation acute coronary syndrome (ACS), maintaining antegrade flow in the coronaries with prevention of distal embolization is important. The Thrombolysis in Myocardial Infarction (TIMI) risk model is a validated mechanism to determine prognosis and guide therapy in patients with ACS. The model consists of seven variables, with one point for each variable: age > 65 years, three or more risk factors for heart disease, known coronary stenosis, multiple anginal episodes in the last 24 hours, use of aspirin in the last week, electrocardiographic changes, and elevated cardiac biomarkers (Table 36.1). High-risk patients are typically admitted to a coronary care unit for management with antiplatelet and antithrombotic therapies. Urgent (within hours) cardiac catheterization and appropriate revascularization are recommended in these patients. Intermediate-risk angina patients are directed to a monitored telemetry unit and undergo further risk stratification such as stress testing and assessment of left ventricular function with possible cardiac catheterization. The lowest risk patients can be observed in a chest pain unit or discharged directly to home, depending on the clinical situation.
C. Assessment of chest pain in ED involves careful patient history, physical examination, and 12-lead electrocardiogram (ECG). Functional stress tests can supply additional data, but the data are not immediately available, and triage decisions are often made without them. With clinical history, physical examination, and initial ECG, 92% to 98% of cases of AMI and approximately 90% of cases of unstable angina can be identified.
TABLE 36.1 Rate of Complications in Non-ST-Segment ACS Based on TIMI Risk Score | |||||||||||||||||||||||||||||||||||
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II. CLINICAL PRESENTATION
A. History
1. Chest pain. The initial history should accurately characterize the location and duration of the patient’s discomfort, associated symptoms, and aggravating and alleviating factors (Table 36.2). Most patients with ischemic chest pain describe it as substernal pressure, squeezing feeling, or a sensation of suffocation. Some patients describe it as aching, burning, or tightness. The pain may radiate to the shoulder, neck, jaw, left or right arm, and the fingertips. Occasionally, the pain may be predominantly epigastric or interscapular.
2. Atypical presentations. Dyspnea is often associated with chest pain during an MI. Dyspnea may also be the only major presenting symptom in about 10% of patients with MI. Other atypical presentations include fatigue, syncope, altered sensorium, stroke, nausea or vomiting, and lethargy. Atypical presentations of AMI are more common in the elderly, in patients with diabetes, and in women.
3. Risk factors. Although several clinical factors have been associated with an increased risk of cardiovascular disease, only the age of patient, history of coronary artery disease, and male sex are predictive of ACS among patients with chest pain. In some studies, diabetes and family history have been associated with ACS, but the overall power of these risk factors in predicting an ischemic event is low. The absence of risk factors cannot be used to exclude cardiac ischemia.
B. Physical examination
1. The physical examination helps to identify signs of left ventricular dysfunction and occult valvular heart disease. The presence of a third heart sound (S3 gallop), rales, sinus tachycardia, hypotension, and increased jugular venous distention is associated with adverse outcome. The presence of these signs and symptoms indicates cardiac origin of the chest pain. A thorough physical examination also helps identify the cause of nonischemic chest pain. Chest wall tenderness, skin lesions, and pleural or pericardial rub can be useful in this regard.
TABLE 36.2 Differentiating Cardiac from Noncardiac Chest Pain | ||||||||||||||||||||||||||||||||
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2. Response to treatment is not reliable in unraveling the cause of chest pain. Pain relief after administration of nitroglycerin does not necessarily point to MI or unstable angina, as other etiologies for chest pain are relieved with nitroglycerin.
III. DIAGNOSTIC TESTING
A. The ECG is integral to the evaluation of chest pain and has important diagnostic and prognostic value. It is even more important in the evaluation of persons with diabetes and elderly persons who tend to have atypical symptoms.
1. Almost 50% of patients with MI have a normal or nondiagnostic ECG on presentation to the ED. Sensitivity depends on a number of factors, including the time from symptom onset, coronary distribution of ischemia, baseline ECG abnormalities, and patient characteristics. Electrocardiographic findings should normalize rapidly after resolution of chest pain. The electrocardiographic findings of a patient who does not have active chest pain are difficult to interpret.
Circumflex distribution ischemia is notoriously silent on an ECG, as the posterolateral wall is underrepresented on a conventional 12-lead ECG.
