UNEXPLAINED SYNCOPE EVALUATED BY ELECTROPHYSIOLOGIC STUDIES AND HEAD-UP TILT TESTING

Objective: To determine the clinical characteristics of subgroups of patients with unexplained syncope having electrophysiologic studies and head-up tilt testing and to assess the efficacy of various therapies. Design: Retrospective study. Setting: Inpatient services of a tertiary referral center. Patients: Eighty-six consecutively referred patients with unexplained syncope. Measurements: All patients had electrophysiologic examinations. Patients with negative results subsequently had head-up tilt testing. Main Results: Twenty-nine (34%) patients (group 1) had abnormal electrophysiologic results, with sustained monomorphic ventricular tachycardia induced in 72%. Thirty-four (40%) patients (group 2) had syncope provoked by head-up tilt testing. The cause of syncope remained unexplained in 23 (26%) patients (group 3). Structural heart disease was present in 76%, 6%, and 30% of groups 1, 2, and 3, respectively. In group 1, pharmacologic or nonpharmacologic therapy was recommended based on electrophysiologic evaluation. All group 2 patients had negative results on head-up tilt testing while receiving oral beta blockers (27 patients) or disopyramide (7 patients). Group 3 patients did not receive any specific therapy. During a median follow-up period of 18.5 months, syncope recurred in 9 (10%) patients. Conclusions: The combination of electrophysiologic evaluation and head-up tilt testing can identify the underlying cause of syncope in as many as 74% of patients presenting with unexplained syncope. Therapeutic strategies formulated according to the results of these diagnostic tests appear to prevent syncope effectively in most patients.