54 Chest Pain
Key Points• Observation and repeated testing are extremely valuable in a patient with chest pain in whom the diagnosis is unclear.
• Rapid ruling out of acute myocardial infarction can be performed with serial cardiac marker testing once an appropriate interval after symptom onset has elapsed (8 hours for troponin I or T), although shorter intervals may be acceptable if immediate stress testing is performed.
• Normal cardiac marker values do not exclude unstable angina.
• Consider life-threatening diagnoses other than acute myocardial infarction in patients with chest pain, including aortic dissection, which is frequently missed and often manifested atypically.
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
Visceral pain, from internal structures such as the heart, lungs, esophagus, and aorta, may be difficult for the patient to define or localize. It is experienced as discomfort or a vague sensation and is often difficult to pinpoint.
Somatic pain, from chest wall structures and the parietal pleura, is often easier to describe and localize. Somatic pain may be sharp or stabbing and exacerbated by movement or position.
Referred pain, from irritation or inflammation of the upper abdominal contents, is a form of visceral pain that may be perceived in the chest wall, shoulder, or upper part of the back.
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.
Box 54.2 Approach to Patients with Chest Pain
• Use the term discomfort as opposed to pain to facilitate communication.
• Do not ascribe partially reproducible pain to a musculoskeletal cause. Pain arising from inflammation of the pericardium (secondary to AMI or pericarditis) or inflammation of the pleura (pulmonary embolism, pneumonia, or pleurisy) can be partially reproduced by palpation.
• Chest pain that is completely pleuritic (present only on inspiration) or completely reproducible significantly decreases suspicion for cardiac causes and raises suspicion for pulmonary or musculoskeletal causes. Partially pleuritic (worse with inspiration) or partially reproducible chest pain has much less predictive value.
• Substantial evidence suggests that responses to treatments such as sublingual nitroglycerin or a “gastrointestinal cocktail” do not differentiate the etiology of the chest pain.
• Do not overestimate the value of low-risk features when high-risk features are present (i.e., pain that is completely pleuritic but radiates to the left arm should still raise concern for possible acute coronary syndrome).
• The history and physical examination of patients with nonspecific chest pain are inadequate to justify discharge without further evaluation.
Acute Coronary Syndrome
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:
• Patients with definite acute coronary syndrome are those with (1) changes diagnostic of ischemia or infarction on an ECG, (2) diagnostic elevation of serum cardiac markers, or (3) evidence of new heart failure or shock directly attributable to an acute ischemic event.
• Patients with probable acute coronary syndrome are those in whom suspicion for acute coronary syndrome is high but definitive criteria are lacking. An example is a patient with a classic history for acute coronary syndrome or whose cardiac marker values are slightly elevated but still below the diagnostic cutoff and who does not have clear ECG evidence of ischemia.
• Patients with possible acute coronary syndrome constitute the majority of patients with chest pain. They have atypical histories, their ECG findings are normal or unchanged from previous studies, or suspected alternative causes are triggering their symptoms.
