Impact of Enalapril on Reflex Vagal Activity After Acute Myocardial Infarction: Probable Prognostic Improvement

Baroleflex sensitivity (BRS) is predictor of lethal arrhythmias and cardiac sudden death after acute myocardial infarction (AMI). Despite the fact that angiotensin convertign enzyme inhibitors (ACEI) were shown to increase the vagal activity, their effects on BRS after AMI are yet to determined. Hence, we aimed to assess the effects of ACEI on BRS values after AMI. 15 cases with anterior AMI, who were given early thrombolytic therapy, were enrolled into the study. After phenylephrine test was performed on the third of fourt in-hospital days to obtain BRS values, 10 randomized cases were given enalpril 5 mg bid orally, and the remaining 5 were included in the control group. The phenylephrine test was repeated three days later. While the mean BRS value rose from 5.6±3.6 msec/mmHg to 8±4.5 msec/mmHg (p<0.001) after enalapril administration, it decreased from 9±7.5 msec/mmHg to 7.4±5.2 msec/mmHg in the control group. BRS increase of about 2.4±1.6 msec/mmHg induced by enalapril was significantly different from the BRS decrease of about 1.6±3.6 msec/mmHg that was determined as control value, although the difference between the corresponding first and second mean BRS values among the two groups were not statistically significant (p>0.2, p>0.3). Thus, enalapril significantly improves reflex vagal activity in uncomplicated AMI cases during in-hospital days.