Cerebrovascular variability interactions after acute ischemic stroke: insights from directionality analysis based on...

Area of Science:

• Neuroscience
• Cardiovascular Physiology
• Biomedical Engineering

Background:

• Dynamic cerebral autoregulation (CA) maintains stable cerebral blood flow despite arterial pressure changes.
• CA is impaired after acute ischemic stroke (AIS), affecting cerebrovascular control.
• Traditional methods often overlook the bidirectional influence between mean arterial pressure (MAP) and mean cerebral blood velocity (MCBv).

Purpose of the Study:

• To assess directional information transfer between MAP and MCBv using transfer entropy (TE) and conditional TE (CTE) in AIS patients.
• To compare novel directional markers with traditional indices for evaluating CA impairment.
• To investigate the closed-loop dynamics of the MAP-MCBv relationship in the context of AIS.

Main Methods:

• Utilized transfer entropy (TE) and conditional TE (CTE) to quantify directional interactions between MAP and MCBv.
• Analyzed data from 34 controls and 48 AIS patients within 48 hours of stroke onset.
• Measured MCBv via transcranial Doppler ultrasound, accounting for partial pressure of end-tidal carbon dioxide.

Main Results:

• AIS patients showed hypertension, hypocapnia, and reduced MCBv, particularly in the affected hemisphere.
• TE and CTE decreased from MAP to MCBv but increased from MCBv to MAP.
• Traditional CA indices failed to detect these differences, highlighting the limitations of conventional assessments.

Conclusions:

• CA impairment in AIS is characterized by an imbalance in the MAP-MCBv closed loop, with diminished pressure-to-flow and enhanced flow-to-pressure information transfer.
• Assessing the MAP-MCBv relationship in a closed-loop manner is crucial for understanding cerebrovascular control after stroke.
• Directional analysis provides novel insights into CA modifications post-AIS, complementing traditional methods.