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

Abstract

The cardioprotective role of hormonal replacement therapy remains in doubt, but interest is increasing in the vascular effects of estrogens especially in coronary circulation. 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). 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). 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.