Non-ACS Chest Pain
Some etiologies are life-threatening, and you should know them
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Objectives
• Discuss pathophysiology of chest pain
• Review signs and symptoms of esophageal rupture
• Review signs and symptoms of aortic dissection, AMI and pulmonary embolism
In 2008 about 6.4 million persons over age 15 presented to emergency departments with complaints of chest pain. That represented about 6.3% of all visits for persons in this age group in the United States.1
Because of its high incidence and potential mortality, EMTs and paramedics spend considerable time learning to identify and treat acute coronary syndrome (ACS). Although they occur less frequently, there are also non-ACS etiologies of chest pain that are potentially life-threatening and with which prehospital providers should be familiar. These include pulmonary embolism, pneumothorax, pericarditis with tamponade and esophageal rupture. In addition, there are numerous etiologies of non-ACS chest pain that are less lethal but still require transport to an ED.
This month’s article uses a case-based approach to highlight two of the more frequent non-ACS causes of chest pain, as well as one of the more lethal. It walks through differential diagnoses to show how to evaluate and weigh the evidence for and against the various etiologies of non-cardiac chest pain and arrive at a best guess for a diagnosis.
Pathophysiology of Chest Pain
Understanding the pathophysiology of chest pain is an important component of understanding how chest pain from any etiology is perceived by the patient.
In the nervous system, efferent nerves (motor neurons) carry signals away from the central nervous system (CNS) to effectors such as glands or muscles. Afferent neurons (sensory or receptor neurons) carry nerve impulses from sense organs and receptors back toward the CNS. Stimulation of somatic or visceral afferent pain fibers results in two distinctly different perceptions of pain. Somatic nerve fibers innervate the skin and parietal pleura in the lungs, and enter the spinal cord at specific levels along its length. This specificity allows for the creation of dermatomes, areas of skin primarily innervated by single nerves. As a result, pain from somatic nerve fibers is typically perceived by the patient as sharp and can be precisely located and easily described. Think of a patient with a fractured rib—she can easily describe the pain and point to exactly where it hurts.
Visceral afferent nerve fibers innervate the internal organs, including the heart, visceral pleura, lungs, aorta and esophagus. These nerves from the various thoracic organs enter the spinal cord at multiple levels, rather than single specific levels, as with somatic nerves. This nonspecific relationship with the spinal cord results in the imprecise nature of visceral pain, which is often described as a heaviness, aching or discomfort. As a result, the origin of visceral pain is often difficult to determine and can be perceived anywhere from the epigastrium to the jaw.
In addition, the sensation of radiation is created when a visceral afferent nerve fiber enters the spinal cord at the same level as a somatic afferent nerve fiber. As a result, the visceral pain is often attributed to an area of the body innervated by the somatic nerve fiber. This is why the patient with irritation of the diaphragm will experience shoulder pain, and the patient with myocardial ischemia may experience neck, jaw or arm pain.2Table 1 lists the etiologies of non-cardiac chest pain that will be discussed in this article. This list is not exclusive, but meant to fall within a realistic spectrum of illness about which prehospital providers learn and may see regularly.
