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Updated: Aug 7, 2026
A Methodological Approach to Non-invasive Assessments of Vascular Function and Morphology
Published on: February 7, 2015
M-wave analysis and passive tilt in patients with different degrees of carotid artery disease
C Haubrich1, A Klemm, R R Diehl
1Departments of Neurology Neuroradiology, University Hospital Aachen, Aachen, Germany. christina.haubrich@t-online.de
Insights
Cross-spectral analysis (CSA) of Mayer-wave (M-wave) oscillations is superior to passive tilting for assessing cerebral autoregulation in carotid artery disease (CAD). Autoregulation capacity depends on CAD severity, collateralization, and prior strokes.
Area of Science:
- Neuroscience
- Vascular Medicine
- Medical Technology
Background:
- Carotid artery disease (CAD) significantly impairs cerebral autoregulation, increasing stroke risk.
- Therapeutic strategies for CAD depend on disease severity, necessitating accurate assessment of autoregulatory capacity.
Purpose of the Study:
- To investigate the relationship between the degree of carotid artery disease and cerebral autoregulatory capacity.
- To compare the efficacy of cross-spectral analysis (CSA) and passive tilting (PT) in assessing cerebral autoregulation.
Main Methods:
- Cerebral autoregulation was assessed in 102 patients with severe carotid stenosis or occlusion and 14 controls.
- Methods included continuous transcranial Doppler sonography, beat-to-beat arterial blood pressure monitoring during passive tilting, and CSA of M-wave oscillations.
Main Results:
- Passive tilting showed lower sensitivity and specificity for assessing autoregulation compared to CSA.
- CSA revealed gradually lowered phase angles with increasing carotid stenosis, moderately correlated with CAD severity (r = -0.35).
- Collateralization sufficiency and prior strokes influenced autoregulatory capacity.
Conclusions:
- Cross-spectral analysis of M-waves is a more appropriate method for testing cerebral autoregulation than passive tilting.
- Cerebral autoregulation capacity is influenced by the degree of carotid artery disease, collateral pathways, and pre-existing strokes.
Background And Purpose:
Carotid artery disease (CAD) is able to critically impair cerebral autoregulation which increases the risk for stroke. As therapeutic strategy largely depends on the degree of CAD, we investigated whether this gradation is also related to significant changes in autoregulatory capacity. We applied cross-spectral analysis (CSA) of spontaneous Mayer-wave (M-wave) oscillations and passive tilting (PT) to test cerebral autoregulation.
Methods:
Cerebral autoregulation was tested in 102 patients with carotid stenosis (> or =70%) or occlusion and 14 controls by comparison of continuous transcranial Doppler sonography of the middle cerebral artery and beat-to-beat arterial blood pressure (ABP) during PT to 80 degrees head-up position as well as by CSA of M-waves (3-9 cpm).
Results:
The orthostatic decrease of cerebral blood flow velocity (CBFV) was not correlated with the degree of CAD and showed a lower sensitivity and specificity than phase angle shifts between M-waves in ABP and CBFV (sensitivity: 75-80%, specificity: 86%). Phase angles were gradually lowered in carotid stenoses > 70%, but apparently, they were only moderately correlated with the degree of CAD (r = -0.35, P < 0.01). An additional influencing factor seemed to be the sufficiency of collateralization.
Conclusions:
The results show that CSA of M-waves is more appropriate for testing autoregulation than PT. CSA suggests that the capacity to autoregulate depends to a certain extent on the degree of CAD but is also influenced by the sufficiency of collateral pathways and pre-existing strokes.
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