A practical approach to investigation of syncope

Syncope is caused by cerebral hypoperfusion. Most fainting is simply vasovagal syncope and the challenge lies in identifying the few patients who have potentially life-threatening causes of syncope. Syncope patients constitute 1%-2% of emergency department visits and approximately 30%-50% are admitted to hospital. The known causes are vasovagal syncope (50%), and orthostatic hypotension and cardiac syncope (7% each). Structural heart disease is noted in 3%. The 30-day mortality is only 0.7%, and the 30-day adverse outcome is 4.5%. Risk stratification and diagnosis are important. High-risk patients might have a fatal cause, and low-risk patients do not. Risk markers include syncope while supine or with marked exertion, without a prodrome, with structural heart disease or heart failure, with a family history of sudden death, and with an abnormal electrocardiographic findings. Ischemic heart disease and hypotension are also risk factors. The history captures the preceding situation or activity, prodromal symptoms, and symptoms after syncope. Very simple diagnostic scores exist to help. Investigations beyond an electrocardiogram are not usually needed, and aim to: (1) assess whether a structural substrate exists; (2) capture risk factor data, assuming it is related to the syncope; (3) capture data during clinical syncope; and (4) induce syncope under controlled conditions. The most commonly used tests are implantable loop recorders, which establish a diagnosis in 30%-40% of patients over 2-3 years; and tilt table testing. Neither are needed most of the time. A good history provides more useful and more accurate information in most patients.