Syncope: An evidence-based approach

Abstract

Syncope is a transient loss of consciousness with loss of postural tone due to transient cerebral hypoperfusion with spontaneous recovery, usually after a short period of time. It is important to appreciate that not all transient loss of consciousness (TLOC) is due to syncope. The differential diagnosis for TLOC can be divided into cardiac and noncardiac causes. Cardiac causes which result in syncope can be broadly grouped into those due to autonomic nervous system dysfunction, cardiac arrhythmias, and obstruction to blood flow. Noncardiac causes of TLOC can be categorized into neurologic, metabolic, and psychogenic etiologies. Syncope is a common reason for requesting a cardiology consultation. In general, there are two main reasons for evaluating patients who present with possible syncope. The first is to identify the underlying etiology of syncope, in order to initiate specific therapy aimed at the cause. The second reason is to better risk-stratify the patient, especially with respect to sudden death. Patients with structural heart disease are at higher risk for death following an episode of cardiac syncope. This chapter reviews the differential diagnosis, pathophysiology, and steps to arrive at a diagnosis for the various etiologies of syncope and provides an evidence-based approach to management of these patients.