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Syncope: Evaluation and Differential Diagnosis

This is a corrected version of the article that appeared in print.

Max Bayard, MD
Fereshteh Gerayli, MD
James Holt, MD

American Family Physician. 2023;108(5):454-463.

Author disclosure: No relevant financial relationships.

Syncope is an abrupt, transient, and complete loss of consciousness associated with an inability to maintain postural tone; recovery is rapid and spontaneous. The condition is common, resulting in about 1.7 million emergency department visits in 2019. The immediate cause of syncope is cerebral hypoperfusion, which may occur due to systemic vasodilation, decreased cardiac output, or both. The primary classifications of syncope are cardiac, reflex (neurogenic), and orthostatic. Evaluation focuses on history, physical examination (including orthostatic blood pressure measurements), and electrocardiographic results. If the findings are inconclusive and indicate possible adverse outcomes, additional testing may be considered. However, testing has limited utility, except in patients with cardiac syncope. Prolonged electrocardiographic monitoring, stress testing, and echocardiography may be beneficial in patients at higher risk of adverse outcomes from cardiac syncope. Neuroimaging should be ordered only when findings suggest a neurologic event or a head injury is suspected. Laboratory tests may be ordered based on history and physical examination findings (e.g., hemoglobin measurement if gastrointestinal bleeding is suspected). Patients are designated as having lower or higher risk of adverse outcomes according to history, physical examination, and electrocardiographic results, which can inform decisions regarding hospital admission. Risk stratification tools, such as the Canadian Syncope Risk Score, may be beneficial in this decision; some tools include cardiac biomarkers as a component. The prognosis of patients with reflex and orthostatic syncope is good; cardiac syncope is more likely to be associated with adverse outcomes.

Syncope is an abrupt, transient, and complete loss of consciousness associated with an inability to maintain postural tone; recovery is rapid and spontaneous. The definition of syncope does not include loss of consciousness caused by other conditions, such as seizures or head trauma. Presyncope refers to the symptoms that occur before an episode of syncope, such as graying out or tunnel vision; these symptoms may progress to syncope or resolve without total loss of consciousness.1

SORT: KEY RECOMMENDATIONS FOR PRACTICE

Clinical recommendation Evidence rating Comments
History, physical examination (including orthostatic blood pressure), and electrocardiographic results should be obtained in individuals presenting with syncope.1,5 C Consensus guidelines
Neurologic imaging, including carotid ultrasonography and computed tomography or magnetic resonance imaging of the head, should not be ordered as part of the evaluation for syncope in the absence of neurologic signs or symptoms.1,27 B Expert opinion and systematic review of observational studies showing lack of patient benefit
Individuals who experience syncope during exertion should have an exercise stress test.1,5,12 C Consensus guidelines
Patients with low-risk features suggestive of reflex or orthostatic syncope should be managed without hospital admission.1,5 C Consensus guidelines
Patients with high-risk features suggestive of cardiac syncope should be admitted to the hospital or observation unit.1,5 C Consensus guidelines
Risk stratification scores may be used in the management of patients with syncope, but they have not been shown to be superior to physician judgment.5,36–39 B Systematic reviews and validation studies assessing adverse patient outcomes, but tools did not perform better than physician judgment

A = consistent, good-quality patient-oriented evidence; B = inconsistent or limited-quality patient-oriented evidence; C = consensus, disease-oriented evidence, usual practice, expert opinion, or case series. For information about the SORT evidence rating system, go to https://www.aafp.org/afpsort.

MAX BAYARD, MD, is a professor in the Department of Family Medicine at East Tennessee State University, Johnson City.

FERESHTEH GERAYLI, MD, is a professor in the Department of Family Medicine at East Tennessee State University.

JAMES HOLT, MD, is a professor in the Department of Family Medicine at East Tennessee State University.

Address correspondence to Max Bayard, MD, East Tennessee State University College of Medicine, 917 W. Walnut St., Johnson City, TN 37604 (bayard@etsu.edu). Reprints are not available from the authors.

Author disclosure: No relevant financial relationships.

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