ACUTE EFFECT OF CAPTOPRIL ADMINISTRATION ON BAROREFLEX SENSITIVITY INPATIENTS WITH ACUTE MYOCARDIAL-INFARCTION

Depressed baroreflex sensitivity (BRS) after acute myocardial infarcti on (AMI) is considered an indication of decreased vagal and/or increas ed sympathetic tone. To determine the effect of angiotensin converting enzyme inhibitors (ACEI) on BRS after AMI we studied 27 patients with a first Q wave AMI, no signs of heart failure and no history of arter ial hypertension or diabetes mellitus. An additional group of 10 patie nts with the same clinical characteristics served as controls. On the 5th day after the onset of AMI, three consecutive boluses of phenyleph rine were given intravenously and baseline BRS was taken as the mean s lope of the linear regression lines of RR intervals over systolic bloo d pressure. QT interval was also measured and corrected according to B azett's formula (QTC). Consequently, a single oral dose of captopril 5 0 mg or placebo was given to treatment or control group patients, resp ectively; BRS and QTc were reassessed 1 h later. One hour after captop ril administration BrS increased from 5.95 +/- 2.80 to 9.14 +/- 3.46 m s.mmHg(-1) (P<0.0001); QTc increased from 414 +/- 46 to 425 +/- 46 ms (P<0.0001), systolic blood pressure decreased from 125 +/-19 to 115 +/ - 15 mmHg (P=0.0002), while heart rate did not change significantly. B aseline BRS was correlated only with age (r=-0.74, P<0.0001). In the c ontrol group, 1 h after placebo, no difference was observed in any var iable compared to baseline. Captopril appears to improve BRS immediate ly in the early phase of AMI.