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Functional implications of impaired dynamic cerebral autoregulation in young healthy women; a comparative investigation

By Lawrence Labrecque, Kevan Rahimaly, Sarah Imhoff, Myriam Paquette, Olivier Le Blanc, Simon Malenfant, Audrey Drapeau, Jonathan D. Smirl, Damian M. Bailey, Patrice Brassard

Posted 03 Sep 2018
bioRxiv DOI: 10.1101/406827 (published DOI: 10.14814/phy2.13984)

Women exhibit higher prevalence of orthostatic hypotension with presyncopal symptoms compared to men. These symptoms could be influenced by an attenuated ability of the cerebrovasculature to respond to rapid changes in blood pressure (BP) dynamic cerebral autoregulation (dCA). However, the influence of sex on dCA remains equivocal. We compared dCA in 11 women (25±2 y) and 11 age-matched men (24±1 y) using a multimodal approach including a sit-to-stand maneuver and forced oscillations (5 min of squat-stand performed at 0.05 and 0.10 Hz). The prevalence of initial orthostatic hypotension (IOH; decrease in systolic ≥40 mmHg and/or diastolic BP ≥20 mmHg) during the first 15 sec of sit-to-stand was determined as a functional outcome. In women, the decrease in mean middle cerebral artery blood velocity (MCAvmean) following the sit-to-stand was greater (-20±8 vs. -11±7 cm sec-1; p=0.018) and the onset of the regulatory change (time lapse between the beginning of the sit-to-stand and the increase in the conductance index (MCAvmean/mean arterial pressure (MAP)) was delayed (p=0.007). Transfer function analysis gain during 0.05 Hz squat-stand was ~48% higher in women (6.4±1.3 vs. 3.8±2.3 sec; p=0.017). The prevalence of IOH was comparable between groups (4/9 vs. 5/9, p=0.637). These results indicate the cerebrovasculature of healthy women has an attenuated ability to react to large and rapid changes in BP in the face of preserved orthostasis, which could be related to a higher cerebrovascular reserve to face a rapid transient hypotension.

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