Profound hemodynamic changes are associated with menopause, such as increased total peripheral resistance (TPR) and changes in cardiac output.

To investigate the effects of hormone therapy on these cardiovascular changes, Noha Farag, MD & and his colleagues, Dept.of Psychiatry & Medicine, University of California, San Diego gave 43 postmenopausal women a three-minute public speaking task, during which ECG, impedance cardiography, and blood pressure reading were continually taken.

This study examined the effects of oral estrogen (ERT) alone versus estrogen / medroxyprogesterone acetate (HRT) therapy on cardio-vascular function, as controlled by autonomic nervous system. Participants were then randomised to oral estrogen alone, estrogen/medroxy progesterone acetate (HRT) or placebo for three months, before the task was repeated. Cardiovascular hemodynamics & heart rate variability were assessed at rest during stress.

HRT group showed a significant increase in cardiography determined stroke volume & cardiac out put in response to the stressor with no change in the ERT or placebo groups (P=0.008 & P=0.001 respectively). TPR increased in response to stressor in the ERT & placebo groups & no changes were observed in HRT group. Resting TPR after therapy was also less in HRT women than those on placebo or ERT.

The authors conclude that the combination hormone replacement therapy (HRT) produces a more favourable alternation in cardiac autonomic function than does ERT as HRT produces an increase vagal responsiveness.