The effects of intrinsic sympathomimetic activity on beta-blocker efficacyfor treatment of neurocardiogenic syncope

To compare the efficacy and side effects of beta-blockers with intrinsic sy mpathomimetic activity (ISA) to those without ISA, we retrospectively revie wed patients diagnosed,vith neurocardiogenic syncope (NCS) as determined by head-up tilt table testing. Pour hundred and thirty-one patients (mean age of 57 +/- 25 years) under,vent head-up tilt table testing for syncope of u nknown etiology, of which 120 patients were diagnosed with NCS; 87 of these patients were treated with beta-blocker therapy. Only 56 patients could be contacted during follow-up. Twenty-eight patients were treated with beta-b lockers with ISA (acebutolol or pindolol) and 28 received beta-blockers wit hout ISA (atenolol or metoprolol) based on physician preference and followe d for up to 2 years. During the follow-up period, beta-blockers with or wit hout ISA had comparable clinical efficacy in suppressing recurrent syncope in patients with NCS. However, beta-blockers,vith ISA were better tolerated and caused less fatigue (32% side effects) as compared to those without IS A (50% side effects; p = 0.23). The benefits of betablockers with ISA were more pronounced in patients less than 60 years old (19% side effects with b eta-blocker with ISA as compared to 85% side effects with beta-blocker with out ISA; p = 0.0004). Beta-blockers without ISA appear to be better tolerat ed and caused less fatigue in patients 65 years old or greater (20%) than i n patients less than 65 years old (85%; p = 0.0002).