Timothy C. Hain, MD

Last edited: 7/2002. Please read our disclaimer.

Syncope defined CausesEvaluation Prognosis Education Index


Syncope (faint) is a sudden fall of blood pressure resulting in loss of consciousness. About 3% of the population have syncope at some point in life (Savage, 1985).  Syncope also accounts for 3% of all emergency room visits and 6% of all hospital visits. Between 71 and 125 children and adolescents/100,000 population experience syncope each year. The incidence peaks in 15--19 year olds (Driscoll, 1997).

Presyncope consists of unsteadiness, weakness, or cognitive symptoms without loss of consciousness. It is often a symptom of orthostatic hypotension, and may also be a source of drop attacks (Dey et al, 1997).

Causes of syncope:

Arrythmia -- abnormal slowing or quickness of the heart

hemodynamic -- obstruction to blood flow

Neurally mediated

In the differential diagnosis of syncope one must also consider non-cardiac causes of loss of consciousness:

Common drugs that are associated with an excess risk of syncope in the elderly include

(Source: Cherin et al, 1997)

Evaluation of Syncope:

Physical examination should include at a minimum

Carotid sinus testing may also be helpful. Asessment of balance, such as with the tandem Romberg test, may be useful in excluding alternative causes of falls. According to Linzer and associates, a  careful history, physical examination combined with an ECG will yield a diagnosis in 50% of cases.

Routine Laboratory Testing:

The diagnostic yield of ambulatory event monitoring is 25-35% (Lanzer). The diagnostic yields of echo, stress testing, holter monitoring and electrophysiological studies alone or in combination varies widely (5-35%). The routine ECG is often helpful in identifying abnormalities of rhythm, conduction or morphology of the heart electrical activity that give a clue as to the underlying etiology of the syncope. Recording the ECG during the spell can be achieved by using 24 hour ambulatory recording (also known as Holter monitoring), an event recorder, or a memory loop recorder. 24 hour monitoring is useful in persons who have frequent spells that can be expected to have an event during the 24 hours that they are monitored. Such individuals need to have a non-life threatening spell to make this modality safe. The event recorder and loop memory recorder are useful in persons whose events occure less frequently than every 24 or 48 hours. These devices require the patient or an accompanying person to activate the monitor at the time of symptoms. (Hammill, 1997). Recently implantable monitors have been made available for persons who need chronic monitoring of heart function (i.e Reveal device, made by Medtronic).

In certain situations consider:

The diagnostic yield of EEG, CT scan, and doppler varies from 2-6%. 


30% of people with one syncopal episode have recurrence. In children and adolescents, syncope is a benign event. For patients with cardiac causes, generally an older group, 50% die within 5 years, a third of which due to sudden death. For non-cardiac causes of syncope, excluding children and adolescents, 5-year mortality is 30%.

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