[Electrophysiologic evaluation and follow-up of patients with a syncopal episode of unknown origin].

The etiology of syncope of presumed cardiac origin can be determined by clinical and electrocardiographic examination with Holter monitoring in about 50 per cent of cases. The aim of this study was to review the data of electrophysiological investigation and the outcome of the patients in whom a cardiac pacemaker was eventually implanted, in those cases in whom the initial work-up had been negative. Ninety four patients, all of whom underwent standardised electrophysiological investigation, were included. The results of the investigations enabled us to identify three groups of patients: Group I: patients in whom the criteria did not suggest a cardiac origin of syncope; Group II: with criteria possibly suggesting a cardiac origin and Group III in which the criteria were strongly suggestive of a cardiac origin. A cardiac pacemaker was implanted systematically for AV block in Group III; on the other hand, this was very rare (only 1 patient) in Group I, and the indication in Group II depended on age and the history of recurrent syncope. Ninety patients (96%) were followed up for an average of 39.3 +/- 15.3 months. There was a very low incidence of recurrent syncope irrespective of the original classification, so confirming the value of electrophysiological investigations for cardiac pacemaker implantation in this type of patients. In addition, negative electrophysiological investigations allowed identification of a group of patients with a low mortality and low risk of recurrent syncope.