RANDOMIZED, DOUBLE-BLIND, PLACEBO-CONTROLLED TRIAL OF ORAL ENALAPRIL IN PATIENTS WITH NEURALLY-MEDIATED SYNCOPE

Background The purpose of this study was to study the effect of enalap ril on neurally mediated syncope (NMS). Several agents (except for ang iotensin-converting enzyme [ACE] inhibitors) have been used to treat p atients with NMS. It is unknown whether ACE inhibitors have beneficial effects on NMS. Methods and Results Thirty subjects who had reproduci ble NMS induced with head-up tilt table test (HUT) were randomly assig ned and divided in double-blind fashion into placebo and enalapril (on ACE inhibitor) groups. Hemodynamics and plasma catecholamine concentr ations were studied. Before administration of enalapril, syncope induc ed by HUT was associated with vigorous hypotension and bradycardia. Pl asma catecholamine concentrations were significantly elevated during N MS compared with the supine position before tilt. Oral enalapril rathe r than placebo produced a marked reduction in diastolic blood pressure during supine positioning before tilt. Administration of enalapril pr evented HUT-induced NMS and increase of plasma catecholamine concentra tions in all patients examined. Conversely, placebo had no effect in t he majority of patients with NMS (12 of 15 subjects). Follow-vp data s howed that NMS disappeared in id, (93%) of 15 patients created with en alapril. Conclusions This study demonstrates that ACE inhibitors may e fficiently prevent NMS, presumably through inhibition of sympathetic s ystem activation and peripheral hypotensive effect.