Intracardiac Electrophysiologic Techniques in Recurrent Syncope of Unknown Cause

Abstract

Patients [25] with recurrent episodes of syncope, unexplained despite thorough medical and neurologic evaluation, underwent intracardiac electrophysiologic study with programmed stimulation. Electrophysiologic study yielded a presumptive diagnosis in 17 patients: 9 with rapid ventricular tachycardia induced by programmed stimulation, 3 with intra-His conduction delays, 1 with symptomatic atrial flutter, 1 with sick sinus syndrome and 3 with persistent hypervagotonia manifested as atropine-reversible prolongation of atrioventricular nodal refractoriness. Therapy based on these findings provided complete symptomatic relief in 14 and improvement in 1 of these 17 patients during a mean follow-up of 18 .+-. 10 mo. Therapy based on electrophysiologic testing was ineffective in 2 of the 17 patients. Syncope persisted in 4 of the 8 patients in whom electrophysiologic study did not define a probable arrhythmic mechanism. Full electrophysiologic evaluation with programmed stimulation apparently is useful in the diagnosis and therapy of recurrent unexplained syncope.