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Published on: January 19, 2020
Dynamics of Critical Closing Pressure Explain Cerebral Autoregulation Impairment in Acute Cerebrovascular Disease
Jonathan Ince1, Ronney B Panerai1,2, Angela S M Salinet3
1Cerebral Haemodynamics in Ageing and Stroke Medicine (CHiASM) Group, Department of Cardiovascular Sciences, University of Leicester, Leicester, UK.
Insights
Cerebral autoregulation is impaired in acute ischemic stroke patients. Early transient differences in critical closing pressure dynamics may stem from vascular changes, not regulatory issues.
Area of Science:
- Neurology
- Vascular Physiology
- Stroke Medicine
Background:
- Cerebral autoregulation (CA) impairment is common in acute ischemic stroke (AIS) and linked to poor outcomes.
- The physiological basis for depressed CA in AIS remains unclear.
- This study investigates the role of dynamic critical closing pressure (CrCP) and resistance area product (RAP) responses in AIS.
Purpose of the Study:
- To determine if impaired CA in AIS is associated with altered dynamic responses of CrCP and RAP.
- To compare these dynamic responses between AIS patients and age-matched controls.
Main Methods:
- Continuous monitoring of middle cerebral blood velocity (MCAv), arterial blood pressure (BP), and end-tidal CO2.
- Transfer function analysis to assess dynamic MCAv-BP relationships, estimating CrCP and RAP.
- Comparison of dynamic responses between younger controls, older controls, and AIS patients.
Main Results:
- Dynamic CA was significantly impaired in AIS patients compared to both younger and older controls.
- AIS patients exhibited an early (0-3s) peak in the dynamic CrCP response, independent of age.
- The autoregulation index was lower in AIS patients' affected and unaffected hemispheres.
Conclusions:
- Novel early transient differences in CrCP dynamic response observed in AIS patients.
- These rapid changes occur too early to be explained by regulatory mechanisms.
- Findings suggest potential structural alterations in cerebral vasculature contribute to impaired CA in AIS.
Introduction:
Cerebral autoregulation (CA) is impaired in acute ischemic stroke (AIS) and is associated with worse patient outcomes, but the underlying physiological cause is unclear. This study tests whether depressed CA in AIS can be linked to the dynamic responses of critical closing pressure (CrCP) and resistance area product (RAP).
Methods:
Continuous recordings of middle cerebral blood velocity (MCAv, transcranial Doppler), arterial blood pressure (BP), end-tidal CO2 and electrocardiography allowed dynamic analysis of the instantaneous MCAv-BP relationship to obtain estimates of CrCP and RAP. The dynamic response of CrCP and RAP to a sudden change in mean BP was obtained by transfer function analysis. Comparisons were made between younger controls (≤50 years), older controls (>50 years), and AIS patients.
Results:
Data from 24 younger controls (36.4 ± 10.9 years, 9 male), 38 older controls (64.7 ± 8.2 years, 20 male), and 20 AIS patients (63.4 ± 13.8 years, 9 male) were included. Dynamic CA was impaired in AIS, with lower autoregulation index (affected hemisphere: 4.0 ± 2.3, unaffected: 4.5 ± 1.8) compared to younger (right: 5.8 ± 1.4, left: 5.8 ± 1.4) and older (right: 4.9 ± 1.6, left: 5.1 ± 1.5) controls. AIS patients also demonstrated an early (0-3 s) peak in CrCP dynamic response that was not influenced by age.
Conclusion:
These early transient differences in the CrCP dynamic response are a novel finding in stroke and occur too early to reflect underlying regulatory mechanisms. Instead, these may be caused by structural changes to cerebral vasculature.
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