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

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.

Name dc:type.qualificationname

phd

Level dc:type.qualificationlevel

doctoral

Grantor dc:publisher.institution

University of East Anglia

Year dc:date.issued

2014

Author dc:creator

• Ong, Alice

Language dc:language

en