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The management of the patient with chest pain is a diagnostic and therapeutic challenge of critical importance. Three key chapters in this textbook discuss the identification of acute presentations of ischemic cardiac disease and its differentiation from other life-threatening disorders: the current chapter, Chapter 53, Acute Coronary Syndromes: Acute Myocardial Infarction and Unstable Angina, and Chapter 55, Low Probability Acute Coronary Syndrome. The current chapter covers the assessment of acute chest pain with emphasis on identification of patients with potentially serious disorders and differentiating cardiac disease from noncardiac disease. The Acute Coronary Syndromes chapter discusses ST-segment elevation myocardial infarction (STEMI), non-STEMI (NSTEMI), and unstable angina. The Low Probability Acute Coronary Syndrome chapter discusses the identification and management of the remainder of patients who do not meet criteria for acute coronary syndrome (ACS), yet require further evaluation beyond the immediate ED period.

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Approximately 5% of all U.S. ED visits, or about 5 million visits per year, are for chest pain, but accurate diagnosis remains a challenge.1,2 Owing to a complex interplay of anatomic, physiologic, and psychological factors, serious illness often mimics benign conditions.

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Definitions

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ACS is a constellation of signs and symptoms resulting from an imbalance between myocardial oxygen supply and demand. There are three general classifications: unstable angina, NSTEMI, and STEMI. Unstable angina is a type of ACS with no elevation of biomarkers and no pathologic ST-segment elevation. NSTEMI is characterized by biomarker elevation and no pathologic ST-segment elevation. Acute myocardial infarction (AMI) is characterized by ST elevation and biomarker elevation (STEMI).

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The phrase acute chest pain, commonly used in emergency medicine, deserves discussion. The term acute means of sudden or recent onset. Although there is no precise time period defined, most studies of acute chest pain patients in the ED limit entry to those with symptoms of <24-hours duration. In common practice, acute means that the patient stops his or her usual activity to seek medical attention, typically within minutes to hours. The term chest in this context refers to a location described by the patient on the anterior thorax, between xiphoid and suprasternal notch and between the right and left midaxillary lines. As the major serious thoracic disorders typically manifest symptoms within these regions, thoracic pain localized to the back, between the base of the neck and the lumbar region, is approached differently (see Chapter 276, Neck and Back Pain). Occasional patients with serious and life-threatening intrathoracic disorders will describe the location of their pain outside the anterior thoracic boundaries noted above. Some patients will have migratory pain that is no longer perceived to be in the chest by the time the patient reaches medical attention. Therefore, include significant intrathoracic disorders in the differential diagnosis whenever patients describe symptoms in adjacent regions (e.g., epigastric, neck, jaw, shoulder, and arm). The term pain describes a noxious, uncomfortable sensation. However, pain perception and description vary widely, and patients may use terms such as pressure, heaviness, ache, or discomfort. Be attuned to variation in the patient’s description of the perceived sensation. In summary, ...

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