<< Identifying Emergency Department Patients With Chest Pain Who Are at Low Risk for Acute Coronary Syndromes

Etiology And Pathophysiology

Myocardial ischemia results when myocardial oxygen supply and demand are mismatched. This mismatch activates free nerve endings of visceral afferent sympathetic and vagal fibers originating in the myocardium and causes substernal chest discomfort referred to as angina.13 Sensory afferents of the C1-C2 (neck and jaw) and C5-C6 (upper arm) dermatomes often overlap these fibers, which can cause referred pain from these areas. There is also considerable overlap from sensory afferents of the vagus nerve, phrenic nerve, intercostal nerves, and others. This can give rise to atypical symptoms of myocardial ischemia (known as anginal equivalents), such as shortness of breath or nausea. Alternatively, activation of these pathways by irritation of the esophagus, pleura, or aorta can lead to anginal-type pain from noncardiac sources.14

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