Beneficial effects of long-term treatment with enalapril on cardiac function and heart rate variability in patients with old myocardial infarction

Abstract

Background: The beneficial effects of the early use of angiotensin-converting enzyme inhibitors (ACEis) in patients with acute myocardial infarction (MI) are well documented. However, the effects of ACEis in patients with an old MI and preserved cardiac function have not yet been studied. We examined the effects of 12 months of enalapril treatment in patients with previous MI.

Methods and results: Thirteen patients with an old MI and no overt congestive heart failure (CHF), aged 70 +/- 2 years, were treated with enalapril for 12 months. We also included 13 age- and sex-matched control patients who had a similar clinical background but were not treated with enalapril. Holter electrocardiography and echocardiography were performed at entry and after 12 months of treatment. Heart rate variability, low- and high-frequency powers (LF and HF), and the ratio between LF and HF (LF/HF) were analyzed. Changes from baseline to 12 months in HF, LF/HF, left ventricular end-diastolic dimension (LVEDD), and end-systolic dimension (LVESD) were significantly different in the enalapril group (HF, 8.1 +/- 0.9 to 9.3 +/- 0.9 milliseconds: LF/HF, 1.65 +/- 0.11 to 1.53 +/- 0.16; LVEDD, 57.2 +/- 1.6 to 54.7 +/- 1.6 mm; LVESD, 40.0 +/- 2.4 to 36.3 +/- 1.9 mm) compared with the control group (HF, 8.9 +/- 0.9 to 8.5 +/- 0.7 milliseconds; LF/HF, 1.78 +/- 0.18 to 1.88 +/- 0.15; LVEDD, 52.3 +/- 2.5 to 55.9 +/- 2.2 mm; LVESD, 32.5 +/- 2.6 to 36.1 +/- 2.6 mm; P < .05). The delta change (delta) in LVESD between the end and the start of study correlated inversely with deltaHF (r = -0.56; P < .05) and positively with deltaLF/HF (r = 0.65; P < .01).

Conclusion: Our results suggest possible ongoing structural changes in patients with old MI even in the absence of overt CHF. Enalapril seemed to prevent such changes and to restore cardiac autonomic tone toward normal. Further prospective studies using a larger sample size are warranted to confirm potential beneficial effects of ACEis in patients with previous MI and preserved left ventricular function.