Vasovagal syncope: new physiologic insights.

This review deals with recent changes in understanding of physiologic mechanisms involved in vasovagal syncope. The approach is not comprehensive but attempts to integrate new findings with older studies. The major clinical presentations of the condition and recognized triggers are discussed first, followed by a summary of how new laboratory methods allow better understanding of the vasovagal reflex. A sequence of sympathohemodynamic events during tilt-induced syncope is suggested based on several different research approaches. The aim is to dissect out the different mechanisms for hypotension, then integrate current knowledge and clarify the sequence.