Syncope (medicine)

Syncope (medicine)

Syncope ( /ˈsɪŋkəpi/ SING-kə-pee), the medical term for fainting, is precisely defined as a transient loss of consciousness and postural tone, characterized by rapid onset, short duration, and spontaneous recovery, due to global cerebral hypoperfusion (low blood flow to the brain) that most often results from hypotension (low blood pressure). This definition of syncope differs from others by including the cause of unconsciousness, i.e. transient global cerebral hypoperfusion. Without that addition, the definition of syncope would include disorders such as epileptic seizures, concussion or cerebrovascular accident and syncope needs to be distinguished from coma which can include persistent states of loss of consciousness. This source of confusion may still be found in some literature.

Many forms of syncope are preceded by a prodromal state that often includes dizziness and loss of vision ("blackout") (temporary), loss of hearing (temporary), loss of pain and feeling (temporary), nausea and abdominal discomfort, weakness, sweating, a feeling of heat, palpitations and other phenomena, which, if they do not progress to loss of consciousness and postural tone are often denoted "presyncope". Abdominal discomfort prior to loss of consciousness may be indicative of seizure which should be considered different than syncope.

There are three broad categories of syncope, cardiogenic, reflex and orthostatic hypotension, which underlie most forms of syncope. Cardiogenic forms are more likely to produce serious morbidity or mortality and require prompt or even immediate treatment. Although cardiogenic syncope is much more common in older patients, an effort to rule out arrhythmic, obstructive, ischemic, or cardiomyopathic causes of syncope and circulatory inadequacy is mandatory in each patient.

Variants of reflex syncope often have characteristic histories, including precipitants and time course which are made evident by skilled history taking. Thus, the clinical history is the foremost tool used in the differential diagnosis of syncope. Physical examination, and electrocardiogram are part of the initial evaluation of syncope and other more specific tools such as implantable loop recorders may be necessary in clinically uncertain cases.

Syncope is extraordinarily common, occurring for the most part in two age ranges: the teen age years, and during older age. Estimates of lifetime incidence of at least one syncopal episode include 40-50% of the general populace. Syncope comprises 1-3 percent of all attendances to emergency departments and 1-6 percent of all hospital admissions.

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