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Transfer function analysis of cerebral autoregulation dynamics in autonomic failure patients
A P Blaber1, R L Bondar, F Stein
1School of Kinesiology, Faculty of Health Sciences, University of Western Ontario, London, Canada. cbflab@kinesiology.uwo.ca
Stroke
|September 26, 1997
Summary
Patients with autonomic failure exhibit altered dynamic cerebral autoregulation, showing a higher initial response that normalizes with head-up tilt. This indicates a present, though modified, autoregulatory capacity in autonomic dysfunction.
Area of Science:
- Neuroscience
- Cardiovascular Physiology
- Autonomic Nervous System Research
Background:
- Autonomic nervous system diseases impair systemic blood pressure regulation.
- Patients with autonomic dysfunction experience greater blood pressure drops upon standing.
- These blood pressure changes may impact dynamic cerebral autoregulation.
Purpose of the Study:
- To investigate dynamic cerebral autoregulation in patients with autonomic failure.
- To compare the autoregulatory response between patients and healthy controls during graded head-up tilt.
Main Methods:
- Continuous monitoring of heart rate, middle cerebral artery blood flow velocity (MBFV), and mean arterial blood pressure (MABP).
- Transcranial Doppler ultrasound and Finapres were used for measurements.
- Cross-spectral analysis assessed the dynamic relationship between MBFV and MABP during graded tilt.
Main Results:
- Autoregulation phase angles were similar between patients and controls across all tilt positions.
- Patients with autonomic failure showed higher supine transfer gain compared to controls.
- Both groups exhibited decreased gain with increasing tilt, with no significant difference at 60 degrees.
Conclusions:
- Autonomic failure is associated with an altered dynamic cerebral autoregulatory response.
- Despite alterations, autoregulation remains present in individuals with autonomic dysfunction.
- The study highlights a modified but functional autoregulatory capacity.