Epidemiology

Every year 6.2 million people are seen in U.S. emergency departments (EDs) with complaints of chest pain, which accounts for roughly 6% of ED visits and is the second most common reason for such visits. The differential diagnosis of chest pain ranges from benign causes, such as muscle strain, to the immediately life-threatening ones, such as acute coronary syndrome, pulmonary embolism, and aortic dissection. Although the focus in patients with chest pain remains appropriately on life-threatening causes, a majority of patients have benign or indeterminate diagnoses after ED evaluation. In one study of ED patients with symptoms consistent with acute cardiac ischemia, only 8% had acute myocardial infarction (AMI) and 9% had unstable angina.¹ Another investigation of patients evaluated in the ED for nontraumatic chest pain found that AMI was diagnosed in 4%, unstable angina or stable coronary disease in 7.5%, and pulmonary embolism or aortic dissection in less than 1%.² Given the potentially lethal nature of conditions manifested as chest pain and the lack of sensitivity or specificity, in many instances, of the history and physical examination, the emergency physician (EP) must have an organized approach, a complete differential diagnosis, and a thorough understanding of assessment and management of this common complaint.

Pathophysiology

In the differential diagnosis of patients with chest pain, one must consider the five groups of structures in the thorax: cardiac (heart and pericardium), pulmonary (lungs and pleura), gastrointestinal (esophagus and upper abdominal contents), vascular (aorta and great vessels), and musculoskeletal (chest wall). Chest discomfort is experienced through three distinct pathways, as follows:

A differential diagnosis based on anatomic structures within the chest is presented in Box 54.1.

Presenting Signs and Symptoms

Most patients with nontraumatic chest pain warrant high triage priority and an early electrocardiogram (ECG) (recommended within 10 minutes) to evaluate for AMI. Patient stabilization, evaluation of the history, physical examination, and diagnostic and therapeutic interventions proceed simultaneously. As assessment continues, interventions are refined (Box 54.2). Importantly, the history and physical findings alone are often inadequate to definitively establish or exclude life-threatening diagnoses.

The EP should keep the following points and issues in mind during assessment of a patient with chest pain:

Epidemiology

Several risk stratification systems have been proposed for acute coronary syndrome. These systems have been shown to help in risk stratification, thereby enabling triage decisions. They have never been shown to improve the ability to formulate discharge decisions in comparison with practitioner judgment. The American College of Cardiology and the American Heart Association have published criteria to determine a patient’s risk for coronary artery disease and adverse outcomes from acute coronary syndrome.³ These guidelines are cumbersome and more appropriately applied to patients with documented disease than to undifferentiated ED patients. A simplified approach to stratifying risk is to determine whether the patient has definite acute coronary syndrome, probable acute coronary syndrome, or possible acute coronary syndrome, as follows⁴:

This chapter is focused on patients with possible acute coronary syndrome. After chest radiography, a substantial proportion of such patients require further testing and observation, such as serial cardiac biomarker testing or other tests to evaluate for alternative diagnoses.

The challenge for the EP lies in determining when and which patients with possible acute coronary syndrome can be safely discharged home. At this time no definitive answer exists. A critical error, however, is failure to identify features that warrant further evaluation. Characteristics such as advanced age, known coronary artery disease, diabetes, pain similar to that of a previous myocardial infarction, worsening of typical angina, pressurelike or squeezing discomfort, and radiation of pain to the neck, left shoulder, or left arm have all been shown to increase the likelihood of AMI.

Presenting Signs and Symptoms

The classic manifestation of AMI is discomfort that feels like an elephant sitting on one’s chest; radiates to the left shoulder, arm, or jaw; and is associated with shortness of breath, nausea, or diaphoresis. Patients may describe their discomfort with a clenched fist against their chest, a finding known as the Levine sign. Physical examination demonstrates tachycardia, diaphoresis, and if the infarction has compromised left ventricular function, findings of acute heart failure such as hypoxia, tachypnea, elevated jugular venous pulsations, and bilateral rales. The classic manifestation in patients with unstable angina is a sense of discomfort or pressure that is similar to that of AMI but transient in nature. Patients with unstable angina experience similar associated symptoms typically brought on by exertion and relieved with rest or nitroglycerin. In practice, these classic findings are the exception, not the norm.

Risk factors for coronary artery disease predict a patient’s risk for the development of ischemic heart disease over a period of many years but are only moderately predictive of acute coronary syndrome in the ED. Most important, it is well established that a lack of cardiac risk factors by itself does not place a patient at low risk for acute cardiac events.

Historical and examination features that raise or lower the likelihood of acute coronary syndrome are described in Box 54.3 and Table 54.1