The role of electrophysiologic studies in the management of patients with unexplained syncope.

We evaluated the frequency and type of electrophysiologic abnormalities in an unselected population of consecutive patients with unexplained syncope. Fifty patients were entered in the study; all had 24-hour dynamic electrocardiographic (Holter) recordings and underwent complete electrophysiological studies. An abnormal electrophysiologic study was found in 74% of the patients. Sinus node abnormality was observed in 30%, abnormal AV node function in 14%, long HV in 10%, block distal to H during rapid atrial pacing in 6%, paroxysmal supraventricular tachycardia in 12%, ventricular tachycardia/fibrillation in 8%, and hypersensitive carotid sinus syndrome in 24%. There was no correlation between Holter and electrophysiologic study findings except for the presence of paroxysmal sustained supraventricular tachycardia. Based on clinical, Holter monitoring, and electrophysiologic findings, 38% were treated by antiarrhythmic drugs, 40% received permanent pacemakers, and 22% were not treated at all. During follow-up (23 +/- 13 months), 9 patients (18%) experienced recurrent syncope or death.