Do abnormalities in dynamic cerebral auto-regulation underlie the pathophysiological processes behind syncope in older people?

Ong, Alice (2014) Do abnormalities in dynamic cerebral auto-regulation underlie the pathophysiological processes behind syncope in older people? Doctoral thesis, University of East Anglia.

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Abstract

Do abnormalities in dynamic cerebral auto-regulation underlie the pathophysiological processes behind syncope in older people?
Introduction: The aim of this thesis was to investigate whether abnormalities in dynamic cerebral auto-regulation (dCA) explain the symptoms associated with orthostatic (OH) and post-prandial hypotension (PPH).
Methods: Based on clinical symptoms and signs for the OH study: 4 Groups: Asymptomatic No OH (control), Symptomatic No OH, Asymptomatic OH, and Symptomatic OH. PPH study: double-blind placebo controlled cross-over study of glucose (50g) drink. 2 Groups: No PPH (control) and PPH. Baseline and head-up-tilt (HUT, for OH maximum 30 minutes study or to symptoms; PPH study maximum 60 minutes per visit). All had Transcranial Doppler ultrasound, beat-to-beat BP, ECG and CO2 monitoring. Baseline autonomic function, arterial stiffness, cardiac baroreceptor sensitivity (BRS) were calculated and dynamic cerebral auto-regulation (as the autoregulatory
index ARI) assessed before and during tilt.
Results: OH: n=85, mean age 73.9±7.1 years; PPH: n= 40, mean age 73.4±7.3 years Baseline: No significant differences were found between groups for cardiac BRS,
arterial stiffness, cerebral blood flow velocity (CBFV) or dCA in either study. HUT both studies: falls in BP, CO2 and CBFV, increases in HR, and fall in ARI amongst
symptomatic subjects prior to the end of HUT (maximum duration or symptom onset) compared to pre-HUT values. PPH study: fall in ARI with HUT irrespective of whether glucose or placebo phase.
Conclusions: The development of symptoms during tilt in both studies was related to a fall in CBFV and impaired cerebral auto-regulation. Abnormalities in cerebral autoregulation may explain the symptoms of OH and PPH although these changes can only be detected during head-up-tilt.

Item Type: Thesis (Doctoral)
Faculty \ School: Faculty of Medicine and Health Sciences > Norwich Medical School
Depositing User: Brian Watkins
Date Deposited: 14 Sep 2015 14:14
Last Modified: 14 Sep 2015 14:14
URI: https://ueaeprints.uea.ac.uk/id/eprint/54339
DOI:

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