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INTRODUCTION

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Patients presenting to the emergency department (ED) with chest pain or other symptoms suggesting possible coronary ischemia should be risk-stratified based on the probability of having an acute coronary syndrome (ACS). Patients with a low-probability ACS have no objective evidence of acute coronary ischemia or infarction. These patients do not have characteristic ST-segment elevation or depression on an electrocardiogram (ECG), and initial cardiac biomarkers are not elevated.

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CLINICAL FEATURES

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After performing an initial history and physical examination, an emergency provider needs to determine how much of a diagnostic evaluation to undertake for a patient presenting with chest pain. Approximately 3% to 6% of patients with an initial diagnosis of noncardiac chest pain or another alternative diagnosis may later develop a short-term adverse cardiac event, making risk stratification an important aspect of clinical decision making.

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Among patients who are assessed as low-probability for ACS, aspects that have been shown to be associated with a low-risk profile include chest pain that is described as pleuritic, positional, sharp, stabbing, or that is found to be reproducible. High-risk historical features include chest pain that radiates to the arm or shoulders, is exertional, described as pressure, is accompanied by nausea or diaphoresis, or is similar to prior cardiac pain. However, even patients who present with atypical features may have some risk, and the absence of high-risk features alone cannot completely exclude the possibility of ACS. Significant coronary artery disease is rare in patients <30 years old, although age alone does not completely eliminate ACS as a cause of acute chest pain. In addition, treatment responsiveness to nitrates, antacids, or nonsteroidal anti-inflammatory medications cannot reliably confirm or exclude ACS. Focus the initial evaluation to identify potential alternative diagnoses and detect findings that may be consistent with heart failure or other underlying conditions.

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The results and timing of previous cardiac testing, such as ECG, stress test, and cardiac catheterization, can be helpful to consider when determining the appropriate evaluation for possible ACS. For example, new ECG changes consistent with cardiac ischemia offer strong evidence of underlying cardiac disease. Conversely, a recent negative cardiac catheterization with no coronary luminal irregularities is associated with a very low incidence of myocardial infarction or ACS within a 2-year period. Previous stress test results can add evidence to the clinician’s diagnostic decision making, but cannot confirm the presence or absence of disease.

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DIAGNOSIS AND DIFFERENTIAL

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The evaluation of patients presenting to the ED with possible ACS can be conceptualized into primary and secondary assessments (see Fig. 20-1). The goal of the primary evaluation is to identify patients with definite ACS and differentiate them from those with probable or possible ACS. Identifying patients with alternative causes of chest pain that are unlikely to be ACS should also be considered (see Chapter 17).

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Figure 20-1

Evaluation process for patients with possible acute coronary syndrome (ACS). AMI, acute myocardial infarction.

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The primary evaluation for patients with suspected ACS includes a detailed history, physical examination, ECG, chest radiography as indicated, and cardiac biomarkers. Serial ECGs can be helpful in further evaluating patients with ongoing symptoms or changes ...

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