INHIBITORY EFFECT OF ENALAPRIL ON NEURALLY-MEDIATED SYNCOPE IN ELDERLY PATIENTS

A dramatic increase in catecholamine (CA) concentration is believed to be a primary trigger of the neurally mediated syncope (NMS) in elderl y subjects. The hypercontractile state of the heart might be alleviate d by angiotensin-converting enzyme (ACE) inhibitor through depression of CA release from the sympathetic nerve ending. Thus ACE inhibitor mi ght have positive effect on the prevention of NMS. Tn this study, 24 e lderly subjects who had reproducible NMS induced with head-up tilt tes t (HUT) were randomized and double-blind divided into placebo and ACE- inhibitor groups. The plasma CA concentration [norepinephrine (NE) and epinephrine (E)] were measured during HUT, and the effects of enalapr il on NMS were observed in the two groups. Before administration of en alapril, plasma CA concentrations were significantly increased during HUT compared with those in the supine position; In contrast, administr ation of the enalapril (10 mg/day) for >1 year inhibited the concentra tion of plasma CA increase and prevented syncope in all 12 patients (p < 0.05); however, placebo had no effect on plasma CA concentrations a nd syncope disappeared in only two of 12 patients after administration of placebo. From this study, we conclude that enalapril can prevent N MS in patients, presumably because of its past in the inhibition of CA release from sympathetic nerve endings.