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Chapter Summary

This chapter summarizes the pathophysiology, etiology, diagnosis, and management of syncope (see Fuster and Hurst’s Central illustration). Syncope is a common symptom, characterized by an abrupt, transient, and complete loss of consciousness, followed by spontaneous recovery. The incidence of syncope increases with age, with a lifetime prevalence of 40% and a recurrence rate of 14%. Given the myriad causes and protean manifestations of syncope, the diagnosis is often elusive, and the treatment will vary based on the underlying etiology. There are three main causes of syncope: cardiac (primarily due to arrhythmia or structural heart disease), neurocardiogenic (vasovagal syncope and carotid hypersensitivity), and orthostatic hypotension (dysautonomia, hypovolemia, and medication-induced). Cardiac syncope generally increases the risk of sudden cardiac death if left untreated, whereas neurocardiogenic and orthostatic causes usually follow a more benign course. Syncope, regardless of the cause, may impair quality of life and confer serious physical injury if not properly treated.

eFig 39-01 Chapter 39: Diagnosis and Management of Syncope


Syncope is characterized by an abrupt, transient, and complete loss of consciousness. The presumed mechanism is cerebral hypoperfusion, which leads to the inability to maintain postural tone. Recovery after a syncopal episode is spontaneous.

Syncope can occur suddenly, without warning, or may be preceded by a prodrome of presyncope, including lightheadedness, dizziness but not true vertigo, nausea, a feeling of warmth, diaphoresis, and blurred or tunnel vision. Self-limited episodes of presyncope can occur in the absence of loss of consciousness. Syncope can significantly impact quality of life for patients and their families, particularly when it occurs abruptly without warning, is recurrent, or when it is likely to occur in relation to certain activities. In such cases, patients may need to adjust their lifestyle or even change occupation.

The prevalence of syncope in the general population, as reflected in the Framingham Study, was estimated at 3.0% in men and 3.5% in women over a 26-year follow-up.1 In general, the incidence of syncope increases with age, with a lifetime prevalence of 40%, with a recurrence rate of 14%. Syncope accounts for 1% to 3% of emergency department visits and 6% of hospital admissions.2 As a result, management of syncope is associated with significant resource use and expense—indeed, the annual cost of syncope hospitalizations is approximately $1.7 billion, with up to $26,000 per hospitalization.3


The causes of syncope can be broadly classified into cardiovascular disorders, disorders of vascular tone or blood volume, and cerebrovascular disorders. The relative incidence of these categories varies with the clinical site from which the patients are selected; in hospitalized patients, syncope is most often a result of a cardiovascular disorder, whereas in the emergency room, other causes of syncope predominate.4...

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