Regulation of arterial blood pressure is altered after menopause. The purpose of the
present study was to evaluate whether sympathetic and/or cardiac baroreflex sensitivities
relate to the extent of change in blood pressure seen during vasoactive drug boluses
(modified Oxford) in postmenopausal women. We hypothesized that both sympathetic and
cardiac baroreflex sensitivities would be related to the magnitude of these transients.
Fourteen healthy postmenopausal women (58±6 y) completed the study. Heart rate, arterial pressure, and muscle sympathetic nerve
activity (MSNA) were monitored. Sympathetic baroreflex sensitivity was analyzed using
the slope of the MSNA–diastolic blood pressure (DBP) relationship and cardiac baroreflex
sensitivity was analyzed using the R–R interval (RRI)–systolic blood pressure (SBP)
relationship. MSNA burst incidence (62±4 bursts/100 hb) and burst frequency (38±2 bursts/min) were measured under resting conditions. Mean sympathetic baroreflex
sensitivity slope was −8±1 (AU/beat/mm Hg) and the cardiac baroreflex sensitivity slope was 7±1 (ms/mm Hg). The magnitudes of the acute drops in SBP, DBP, mean arterial pressure (MAP),
and pulse pressure (PP) were associated with cardiac baroreflex sensitivity (r=−0.54, r=−0.54, r=−0.67, and r=−0.50, respectively; p<0.05), but not sympathetic baroreflex sensitivity (p>0.05). Similarly, the return of SBP, DBP, MAP, and PP to near baseline values was
related to cardiac baroreflex sensitivity slopes (r=−0.64, r=−0.77, r=−0.79, and r=−0.53, respectively; p<0.05). The relationship between cardiac baroreflex sensitivity and the magnitude of
change in blood pressure indicates that older women with low cardiac baroreflex sensitivity
have larger transients in blood pressure during vasoactive drug boluses. This suggests
a more prominent role for cardiac (as opposed to sympathetic) baroreflex sensitivity
in responding to acute blood pressure changes in older women. However, further measurements
during situations that simulate orthostasis are needed to evaluate the applicability
of these findings to normal daily activities.
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© 2010 Published by Elsevier Inc.