The effects of metoprolol and captopril on heart rate variability in patients with idiopathic dilated cardiomyopathy.

BACKGROUND: The effects of treatment with captopril or metoprolol on heart rate variability (HRV) were investigated in 38 patients (29 men and 9 women) with mild to moderate symptoms of heart failure due to idiopathic dilated cardiomyopathy (DCM). HYPOTHESIS: The aim of the study was to investigate and compare the effects of the angiotensin-converting enzyme inhibitor captopril with those of the selective beta-adrenergic receptor blocker metoprolol on HRV in patients with idiopathic DCM. METHODS: Heart rate variability was analyzed in the time and frequency domains from 18th of Holter monitoring before randomized treatment was started, after 6 months of therapy, and 1 month after therapy was stopped. RESULTS: Captopril treatment increased HRV expressed as total power and low-frequency power in the frequency domain. There was no change in the time domain. In the metoprolol group, there was a pronounced increase in both time- and frequency-domain indices of HRV. The increase in total power was partly maintained 1 month after therapy was stopped in both treatment groups. CONCLUSION: Treatment with captopril and metoprolol increases HRV in patients with DCM. This effect seems to be maintained for at least 1 month after therapy is stopped. The increase in HRV seems to be more pronounced with metoprolol, and the two different pharmacologic approaches may have additive effects that are of prognostic importance in patients with heart failure.