EFFECT OF CAPTOPRIL ON CARDIAC PARASYMPATHETIC ACTIVITY IN CHRONIC CARDIAC-FAILURE SECONDARY TO CORONARY-ARTERY DISEASE

Thirty-two patients with chronic cardiac failure underwent 24-hour ambulatory electrocardiographic monitoring on 2 separate occasions: 20 patients before and during treatment with captopril, and 12 acting as controls. Heart rate variability was calculated by counting the number of times successive RR interval differences were > 50 ms (this measurement being a reliable index of cardiac parasympathetic activity). During treatment with captopril, group mean total counts increased to 1,032 (range 48 to 7,437) from 482 (range 23 to 6,120) (p = 0.002). There was no change in mean hourly waking or sleeping heart rates. In the control group, no changes were seen: group mean total counts on the first occasion were 340 (range 120 to 3,255) and on the second occasion 400 (range 154 to 3,300) (p = not significant). These results show that treatment with angiotensin-converting enzyme inhibitors increases cardiac parasympathetic activity in patients with chronic cardiac failure. This may be relevant to the improved prognosis of this group of patients when treated with angiotensin-converting enzyme inhibitors.