Estrogen effect on heart rate variability in hypertensive postmenopausal women

Healthy postmenopausal women and hypertensive patients show an imbalance in the modulation of autonomic nervous control of the cardiovascular system, which may increase the cardiovascular risk. Objective: To examine the heart rate variability (HRV) response to estrogen replacement therapy (ERT) and its association with changes in metabolic variables in hypertensive postmenopausal women. Methods: A double-blind, placebo-controlled clinical trial was conducted in 30 hypertensive postmenopausal women receiving 180 mg/day of verapamil. The experimental group (n = 16) received 0.625 mg OD of natural conjugated estrogens during 4 months, while control group (n = 14) received a placebo. Lipids, lipoproteins, apolipoproteins, glucose and insulin were measured at 0, 2 and 4 months. HRV was determined in time and frequency domains using a 24-h Holter before and after ERT. Results: Significant higher values of spectral and non-spectral parameters of HRV, associated with a lower LF/HF ratio, were found at the end of 4 months of ERT. Multiple regression analysis revealed that estrogen treatment itself and changes in total cholesterol, LDL-cholesterol, glucose and waist circumference, contributed to the changes observed in indexes reflecting parasympathetic activity in time and frequency domains. Conclusions: We conclude that ERT partially improves HRV favoring increased parasympathetic drive, and that part of the effect may be mediated by changes in metabolic variables. (C) 2002 Elsevier Science Ireland Ltd. All rights reserved.