syncope: approach to diagnosis

Syncope is a transient loss of consciousness (LOC) due to transient global cerebral hypoperfusion characterized by rapid onset, short duration, and spontaneous complete recovery. Here, the term "transient LOC" encompasses all disorders characterized by self-limited LOC irrespective of the mechanism. Central point in pathophysiology of the development of syncope is fall in systemic blood pressure (BP) with a decrease in global cerebral blood flow. The evaluation and treatment of syncope are very challenging because syncope is not the only cause of transient LOC. Moreover, symptoms of syncope are fleeting, patient is usually asymptomatic at the time of evaluation, and most of the events are often unwitnessed. The guiding principle of assessment is to differentiate syncope from other causes of transient LOC and the more benign causes of syncope from the potentially serious ones. Initial assessment of syncope consists of a detailed history and examination complemented by 12-lead electrocardiography and supine and standing BP. If the cause is suspected, then further investigations may be needed to confirm the particular disorder. A deliberate approach based on initial risk stratification is more likely to give a correct diagnosis. Despite the difficulties, a thorough evaluation of the cause of syncope is warranted in all patients, not just in those deemed to be at high mortality risk. The goal in every case should be to determine the cause with sufficient confidence to provide a reliable assessment of prognosis and treatment options.