Estrogen replacement therapy improves baroreflex regulation of vascular sympathetic outflow in postmenopausal women

Background-Menopausal estrogen loss has been associated with increased card iovascular disease in postmenopausal women. However, the link between estro gen and cardiovascular disease remains unclear. Some data suggest estrogen mediates its effect through changes in arterial pressure and its regulation . However, the data available in older women are equivocal regarding estrog en's ability to reduce resting arterial pressure or to improve its regulati on. Methods and Results-We studied 11 healthy, postmenopausal women before and after 6 months of estrogen administration. Arterial pressure was measured b y brachial auscultation and finger photoplethysmography. Vascular sympathet ic nerve activity was measured in the peroneal nerve by microneurography. a nd the slope of the relations between changes in heart period, sympathetic activity, and arterial pressure caused by bolus infusions of nitroprusside and phenylephrine were used as an index of baroreflex gain. Estrogen therap y did not change systolic pressure (128+/-2 versus 123+/-2 mm Hg) or cardia c-vagal baroreflex gain (6.6+/-0.9 versus 6.7+/-0.7 ms/mm Hg). However, vas cular sympathetic baroreflex gain was increased (similar to4.6+/-0.6 versus -7.4+/-1.0 arbitrary integrated units/mm Hp; P=0.02). Conclusion-These findings suggest long-term estrogen replacement therapy ha s effects on cardiovascular regulation that may not be reflected in resting arterial pressures.