Acute and long-term beta-adrenergic blockade for patients with neurocardiogenic syncope

Abstract

This study was designed to prospectively evaluate the long-term outcome of drug therapy guided by head-up tilt testing for the management of unexplained syncope and near syncope. Head-up tilt testing is used to evaluate patients with unexplained syncope. The validity of acute drug testing and the efficacy of long-term oral therapy for prevention of recurrent syncope have not been investigated in large patient groups. We studied 296 consecutive patients with unexplained syncope or near syncope who underwent 80 degrees head-up tilt testing with and without isoproterenol challenge. The efficacy of intravenous and oral beta-blocker therapy was evaluated by repeat testing. Patients with both positive and negative responses to therapy were followed up for rates of recurrence of syncope. A total of 193 patients (65%) had a positive tilt test response; 89% of these 193 required isoproterenol challenge to elicit this response. Patients with a positive tilt test result had lower values for heart rate at rest (mean +/- SD 69 +/- 13 vs. 74 +/- 14 beats/min, p = 0.046) and systolic blood pressure (137 +/- 28 vs. 145 +/- 30 mm Hg, p = 0.0018) at baseline than did the patients with a negative tilt test result. Intravenous propranolol blocked the positive response in 163 (90%) of 181 patients retested. Oral beta-blockers were effective by tilt test criteria in 118 (94%) of 125 patients; 12 (10%) had recurrent clinical symptoms while taking beta-blockers. Eight (42%) of 19 patients who had a negative tilt test response during beta-blocker therapy had recurrent symptoms when they stopped therapy. Three (23%) of 13 patients receiving empiric beta-blocker therapy had recurrent symptoms. The follow-up period for the patients with a positive tilt test result was 28 +/- 11 months (range 5 to 48). Intravenous propranolol is effective in preventing neurocardiogenic syncope diagnosed during head-up tilt testing and predicts the response to oral beta-blocker therapy. Oral beta-blocker therapy prevents recurrent syncope in the majority of patients. Recurrence of syncope is lowest when efficacy of oral beta-blocker therapy is confirmed by repeat head-up tilt testing.