Autonomic dysfunction affects dynamic cerebral autoregulation during Valsalva maneuver: comparison between healthy...

Area of Science:

• Neuroscience
• Cardiovascular Physiology
• Autonomic Nervous System Research

Background:

• Cerebral autoregulation (CA) maintains stable cerebral blood flow (CBF) despite arterial blood pressure (ABP) fluctuations.
• The role of the autonomic nervous system (ANS) in dynamic CA is not fully understood.
• Autonomic failure (AF) may compromise the brain's ability to regulate blood flow.

Purpose of the Study:

• To investigate the impact of autonomic failure (AF) on dynamic cerebral autoregulation (CA) during the Valsalva maneuver (VM).
• To compare cerebrovascular responses in individuals with AF (familial amyloidotic polyneuropathy - FAP) versus healthy controls during VM.

Main Methods:

• Continuous measurement of arterial blood pressure (ABP) and cerebral blood flow velocity (CBFV) using Finapres and transcranial Doppler.
• Evaluation of cerebrovascular resistance index (CVRi), critical closing pressure (CrCP), and resistance-area product (RAP) changes.
• Calculation of dynamic CA using the time-varying autoregulatory index (ARI(t)).

Main Results:

• Subjects with AF exhibited significantly greater reductions in normalized CBFV, ABP, and RAP during phase II of the VM compared to controls.
• Both groups showed similar increases in CrCP and CVRi during the strain phase.
• The biphasic ARI(t) response observed in controls was blunted in individuals with AF, indicating impaired dynamic CA.

Conclusions:

• Dynamic cerebral autoregulation is a time-varying process during the Valsalva maneuver.
• Autonomic dysfunction significantly disturbs dynamic cerebral autoregulation.
• The RAP + CrCP model provides deeper insights into cerebral hemodynamics, revealing a higher vasodilatory response in AF patients, contrary to CVRi findings.