Mechanism and Prognosis of Syncope in Acquired and Inherited Cardiac Disorders

Abstract

The overall prognosis of patients with syncope depends on the severity and type of underlying heart disease. Major differences in syncope study populations reflect this relationship and underline the difficulty of risk stratification of syncope in unselected mixed syncope populations. For most heart diseases, syncope is an independent marker of adverse prognosis and sudden death compared to patients without syncope often representing a malignant brady- or tachyarrhythmia. Underlying heart disease or not, specifically cardiac syncope is associated with adverse prognosis. The mechanism of syncope reflects the underlying heart disease with increasing likelihood of arrhythmic syncope in more severe heart diseases and increasing likelihood of reflex syncope in less severe heart disease. In selected acquired or inherited heart diseases syncope may be associated with increased mortality independently of the proposed causal mechanism. This review focuses primarily on the mechanism and prognosis of patients with various heart diseases and syncope compared to those without syncope. Further the review discusses risk factors and establishes the overall prognosis of syncope in mixed syncope populations.