Estrogen-induced improvement in coronary flow responses during atrial pacing in relation to endothelin-1 levels in postmenopausal women without coronary disease.

BACKGROUND: The cardioprotective role of hormonal replacement therapy remains in doubt, but interest is increasing in the vascular effects of estrogens especially in coronary circulation. METHODS: Coronary blood flow (CBF) was measured in 24 postmenopausal women (age 55+/-3 years), whose coronary arteries appeared angiographically normal, during incremental atrial pacing (AP) before and 20 minutes after intracoronary administration of either 75 ng/mL 17-beta estradiol (treated group, n=18) or 0.9% saline (controls, n=6). RESULTS: Before estrogen, no differences in the coronary vasomotor responses at AP between the two groups (p=NS) could be detected. After estrogen, in the treated group, at the peak of the second AP, the coronary artery diameter decreased by 0.17 mm (p<0.005) while the CBF increased by 61 mL/min (p<0.05). These changes differed significantly from those observed at the peak of first AP (p<0.001 for both cases). In contrast, in the control group no such changes were observed. The endothelin-1 (ET-1) levels in the coronary sinus were significantly reduced after estrogen infusion, which was negatively correlated with the degree of coronary artery constriction (r= -0.40, p=0.03) and positively correlated with the increase in CBF (r=0.54, p=0.01). CONCLUSIONS: In postmenopausal women without coronary artery disease, the intracoronary estrogen infusion mediates a greater increase in CBF and is positively correlated with the reduction of the coronary sinus ET-1 levels at the peak of AP.

Conjugated estrogen administration improves common carotid artery elastic properties in normotensive postmenopausal women.

BACKGROUND: Various vascular effects of estrogens have been proposed to explain further the beneficial effect of replacement therapy in cardiovascular events. HYPOTHESIS: The study was undertaken to assess the effect of conjugated estrogen on the elastic properties of the large arteries in normotensive, healthy, postmenopausal women. METHODS: Toward this end, we investigated the acute effect of conjugated estrogen on the elastic properties of the common carotid artery (CCA) in 20 normotensive, healthy, postmenopausal women (age 54+/-3 years) at baseline and 20 min after the intravenous administration of 1.25 mg conjugated estrogens. The CCA distensibility was derived by a combination of surface ultrasonographic data and simultaneous blood pressure measurements at the brachial artery. The carotid pulsatility index, a measure of brain impedance, was determined electronically by tracing the CCA Doppler waveform. RESULTS: At baseline, CCA distensibility had a negative correlation with both patients' age and time since menopause (r = -0.57 and r = -0.48, p < 0.05 for both cases). After estrogen administration, estradiol and estrone plasma levels were restored to the range of usual premenopausal values. Estrogen induced a significant increase in CCA distensibility by 0.92+/-0.005 dyne(-1) x cm2 x 10(-6) (from 2.03 to 2.95 dyne(-1) x cm2 x 10(-6)) and a significant reduction in CCA pulsatility index by 0.24+/-0.06, (from 2.17 to 1.93) (p < 0.001 for both cases). The improvement in CCA distensibility had a negative correlation with both patients' age and time since menopause (r= -0.46 and r = -0.44, respectively, p < 0.05 for both cases). CONCLUSIONS: Acute conjugated estrogen administration induced an improvement in CCA elasticity and a reduction in brain impedance in normotensive, postmenopausal women. As the age of women and the time since menopause increased, the improvement in carotid distensibility decreased in such selected subjects.