Overview of Syncope

Syncope is one of a number of conditions that result in transient loss of consciousness (TLOC). Syncope is distinguished from other causes of TLOC in that syncope results from transient global cerebral hypoperfusion. In the majority of cases, global cerebral hypoperfusion is the result of a fall in mean arterial pressure (MAP) to such a degree that cerebral blood flow autoregulatory mechanisms fail. A fall in MAP leading to syncope can result from a variety of mechanisms, which are often classified into four broad categories: (1) reflex syncope, (2) orthostatic hypotension, (3) arrhythmia, and (4) structural etiologies. Of these, reflex syncope syndromes are the most common regardless of the patient population being studied. Within a given category, more than one pathophysiologic mechanism may be involved. Initial evaluation is focused on identification of the cause of syncope. The cause of a given patient’s syncope can often be determined with a careful history and physical examination. On occasion, ancillary testing may be needed. Determining the cause of syncope is critical in order to determine an individual patient’s risk of recurrence and risk of morbidity and mortality. The cause of syncope must be established to allow for an effective treatment strategy.