[Effect of angiotensin converting enzyme inhibitor lisinopril on sympathetic heart rate response during exercise in the early phase of acute myocardial infarction].

OBJECTIVES

Sympathetic heart rate response decreases in patients with left ventricular dysfunction. Angiotensin converting enzyme (ACE) inhibitors effectively prevent heart failure after myocardial infarction. However, the effect of ACE inhibitors on heart rate response is not well known. The present study investigated the effect of ACE inhibitors on sympathetic heart rate response in the early phase of acute myocardial infarction.

METHODS

Sixty-five patients with acute myocardial infarction receiving no beta-blocking agents participated in the study. The subjects consisted of 25 patients (mean age 60.2 +/- 10.7 years) treated with ACE inhibitor lisinopril from the initial stage and 40 control subjects (mean age 57.7 +/- 7.6 years). Cardiopulmonary exercise testing with a treadmill was performed using the ramp protocol in the first month and the third month after the onset of the disease. Heart rate (HR) was measured in the resting state (rest) and immediately after peak exercise (peak). At the same time, blood samples were obtained to investigate the changes in the plasma level of norepinephrine (NE). The degree of sympathetic heart rate response was evaluated as follows: (peak HR - rest HR)/¿(peak NE - rest NE)/rest NE¿ x 100.

RESULTS

There were no significant differences between the 2 groups in the first month in anaerobic threshold, peak oxygen uptake and plasma brain natriuretic peptide concentration. Though the change of heart rate was not significant, the change in the plasma level of norepinephrine was significantly lower in the lisinopril group (9.3 +/- 4.4 vs 5.7 +/- 2.8, p < 0.01). In the first month, the heart rate response in the control group was markedly lower than that in the lisinopril group (8.7 +/- 3.5 vs 15.2 +/- 8.5 beats/min/%, p < 0.01). In the third month, the significant difference between the 2 groups disappeared (10.7 +/- 7.9 vs 14.0 +/- 9.7 beats/min/%, NS) due to the increase of the value in the control subjects.

CONCLUSIONS

From these results, we conclude that ACE inhibitors are effective to improve sympathetic heart rate response during exercise in the early phase of myocardial infarction.