[Are the acute effects of transdermal estradiol in postmenopausal women with coronary disease related to changes of the autonomic tone?]

Efficacy of a low dose of estrogen on antioxidant defenses and heart rate variability

This study tested whether a low dose (40% less than the pharmacological dose of 17-β estradiol) would be as effective as the pharmacological dose to improve cardiovascular parameters and decrease cardiac oxidative stress. Female Wistar rats (n = 9/group) were divided in three groups: (1) ovariectomized (Ovx), (2) ovariectomized animals treated for 21 days with low dose (LE; 0.2 mg), and (3) high dose (HE; 0.5 mg) 17-β estradiol subcutaneously. Hemodynamic assessment and spectral analysis for evaluation of autonomic nervous system regulation were performed. Myocardial superoxide dismutase (SOD) and catalase (CAT) activities, redox ratio (GSH/GSSG), total radical-trapping antioxidant potential (TRAP), hydrogen peroxide, and superoxide anion concentrations were measured. HE and LE groups exhibited an improvement in hemodynamic function and heart rate variability. These changes were associated with an increase in the TRAP, GSH/GSSG, SOD, and CAT. A decrease in hydrogen peroxide and superoxide anion was also observed in the treated estrogen groups as compared to the Ovx group. Our results indicate that a low dose of estrogen is just as effective as a high dose into promoting cardiovascular function and reducing oxidative stress, thereby supporting the approach of using low dose of estrogen in clinical settings to minimize the risks associated with estrogen therapy.

Short-term effect of transdermal estrogen on autonomic nervous modulation in postmenopausal women

OBJECTIVE

To evaluate the effect of short-term transdermal estradiol-l7b on cardiac autonomic nervous modulation in postmenopausal women.

DESIGN

Prospective study.

SETTING

A tertiary medical center.

PATIENT(S)

Twenty-one postmenopausal women.

INTERVENTION(S)

Transdermal estradiol or placebo therapy for 3 weeks in randomized, double-blinded, crossover fashion.

MAIN OUTCOME MEASURE(S)

Heart rate variability measures in both time and frequency domains, serum biochemistry, and climacteric symptoms were compared among baseline, placebo and transdermal estrogen therapies.

RESULT(S)

Plasma concentration of estradiol rose significantly from 11.0 +/- 5.2 pg/ml to 48.2 +/- 34.0 pg/ml after transdermal estrogen. The standard deviation of RR-interval increased significantly from 30.3 +/- 9.9 ms (placebo) to 31.3 +/- 7.4 ms (transdermal estrogen), and the coefficient of variation of RR-interval increased significantly as compared with the baseline session. The total power was marginally increased as compared among baseline, placebo, and transdermal estrogen sessions. The irritability symptom decreased significantly after transdermal estrogen therapy, as compared with baseline and placebo treatment.

CONCLUSION(S)

Transdermal estradiol for 3 weeks could significantly increase the global heart rate variability and reduce the irritability symptom in the postmenopausal women. Short-term transdermal estrogen for 3 weeks could improve cardiac autonomic nervous modulation and climacteric symptoms, and might have some cardioprotective effect in postmenopausal women.