Syncope is a common medical problem, which accounts for 3.5% of emergency room visits. It includes diverse clinical etiologies, from cardiac origin with poor prognosis to reflex-mediated hypotension with benign clinical course. Trauma is not rare in patients with syncope, e.g. bruises or lacerations on the head and face were recognized in 17%. Accordingly, patients presenting with syncope may have a risk of sudden cardiac death, or risk of trauma if the episodes are repetitive. It is a physician's task to diagnose syncope and identify its cause. The history is an essential part of the initial evaluation. Electrocardiography (ECG) is necessary in every case. However, organic disease as a cause is identified in 20% of syncope in routine work-up, and the remaining cases are reflex induced hypotension (neurocardiogenic syncope), misdiagnosed arrhythmia, coronary spasm or unknown. Recent investigations suggest the usefulness of provocation to diagnose neurocardiogenic syncope. Two important non-invasive provocations to reproduce syncope are carotid sinus compression and tilt table test. In patients with syncope who visited emergency room, tilt test was positive in 25%, whereas the response to carotid sinus compression was positive in 21%. One or both of the tests was positive in 39%, suggesting that neurally-mediated syncope accounts for a significant number of patients.
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