COMPARISON OF EFFECTS OF ENALAPRIL AND NITRENDIPINE ON CARDIAC SYMPATHETIC NERVOUS-SYSTEM IN ESSENTIAL-HYPERTENSION

Objectives. The purpose of this study was to assess the effects of ena lapril and nitrendipine on the cardiac sympathetic nervous system. Bac kground. Angiotensin-converting enzyme inhibitors and long acting calc ium channel blockers have been widely used in the treatment of cardiov ascular diseases, in some of which sympathetic overactivity plays a ma jor role in the pathophysiology and prognosis. However, little informa tion is available on the effects of these drugs on the cardiac sympath etic nervous system. Methods. I-123.metaiodobenzylguanidine (MIBG) car diac imaging was performed before and 3 months after drug administrati on in 46 patients with mild essential hypertension. Twenty-two patient s were treated with 5 to 10 mg of enalapril once a day, and the other 24 with 5 to 10 mg of nitrendipine once a day For comparison, 20 normo tensive subjects were also studied. Results. There were no significant differences between the basal characteristics in the 2 hypertensive g roups. In both hypertensive groups, both systolic and diastolic blood pressures were significantly reduced to similar levels after the 3-mon th drug treatment. Before the drug treatment, the 2 hypertensive group s had a significantly higher washout rate and lower MIBG uptake than t he normotensive subjects. The heart-to-mediastinum ratio significantly increased (p < 0.0001), with decreased (p < 0.002) washout rate after drug treatment in the enalapril group, but with no significant change s in the nitrendipine group. Conclusion. Enalapril could suppress card iac sympathetic activity and nitrendipine had no effect on it. The kno wledge of antihypertensive drugs on the cardiac sympathetic nervous sy stem appears to be helpful in selecting appropriate treatment in cardi ovascular diseases.