Syncope

Abstract

Syncope is defined as transient loss of consciousness due to reduced cerebral blood fl ow associated with postural collapse and spontaneous recovery. Symptoms and signs that precede syncope may include pallor, diaphoresis, a feeling of warmth, nausea, and visual blurring occasionally proceeding to blindness. Syncope may be benign when it occurs in the absence of heart disease; however, recurrent, unexplained syncope, particularly in an individual with structural heart disease, is associated with a high risk of death (40% mortality within 2 years). Transiently decreased cerebral blood fl ow is usually due to one of three general mechanisms: Disorders of vascular tone or blood volume, cardiovascular disorders including cardiac arrhythmias, or cerebrovascular disease. Often, the cause of syncope is multifactorial. Disorders of vascular tone or blood volume include neurocardiogenic (vasovagal or vasodepressor) syncope, postural (orthostatic) hypotension, carotid sinus hypersensitivity, and situational syncope (associated with cough, deglutition, micturition, defecation). Cardiovascular disorders that cause syncope include arrhythmias and structural disorders (aortic valvular stenosis, hypertrophic cardiomyopathy, atrial myxoma, pulmonary artery hypertension). Cerebrovascular disease, usually involving the vertebrobasilar arteries is an uncommon cause of syncope. The treatment of syncope depends on the underlying cause. Lifestyle and behavioral changes, drugs, and permanent pacing have been used to treat neurocardiogenic syncope. Treatment of the cardiovascular causes of syncope (arrhythmias and structural disorders) is often focused on the underlying cause (myocardial ischemia, valvular disease, etc.). Regardless of the etiology patients with syncope should be hospitalized with continuous electrocardiographic monitoring when the episode may have resulted from a life-threatening abnormality or if recurrence with significant injury seems likely. Patients who are known to have a normal heart and for whom the history strongly suggests vasovagal or situational syncope may be treated as outpatients if the episodes are neither frequent nor severe.