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 w ith idiopathic DCM. Methods: Heart rate variability was analyzed in the time and frequency doma ins from 18 h 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 d omain. In the metoprolol group, there was a pronounced increase in both tim e- and Frequency-domain indices of HRV. The increase in total power was par tly maintained 1 month after therapy was stopped in both treatment groups. Conclusion: Treatment with captopril and metoprolol increases HRV in patien ts 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 me toprolol, and the two different pharmacologic approaches may have additive effects that are of prognostic importance in patients with heart failure.