Syncope: diagnosis of cardiac and noncardiac causes.

Syncope is a sudden and temporary loss of consciousness not caused by trauma or seizures. Patients age 65 and older are at elevated risk of syncope-related falls and sudden cardiac death. Cardiovascular causes are generally electrical (ie, arrhythmias) or mechanical (obstruction of central circulation at a cardiac valve or major vascular structure). Noncardiovascular causes include orthostatic hypotension, vasovagal reaction, micturition, carotid sinus hypersensitivity, and neurologic (eg, TIAs). Many causes of syncope can be diagnosed from a thorough history and physical exam. More extensive testing--ECG, Holter monitoring, electrophysiology study--may be indicated for selected patients with unexplained syncope and an unremarkable evaluation.