Reliability, Asymmetry, and Age Influence on Dynamic Cerebral Autoregulation Measured by Spontaneous Fluctuations of Blood Pressure and Cerebral Blood Flow Velocities in Healthy Individuals

Abstract

Background Cerebral autoregulation (CA) enables the brain to maintain stable cerebral blood flow (CBF). CA can be assessed non-invasively by determining correlations between cerebral blood flow velocity (CBFV) and spontaneous changes in blood pressure. Post-recording signal analysis methods have included both frequency- and time-domain methods. However, the test-retest reliability, cross-validation, and determination of normal values have not been adequately established. Methods In 53 healthy volunteers a transfer function analysis was applied to calculate phase shift (PS) and gain in the low frequency range (0.06-0.12 Hz) where CA is most apparent. Correlation analysis was used to derive mean velocity index (Mx). Intra-class correlation and bivariate correlation coefficients were applied to assess asymmetry, cross-validity, and test-retest Results The bihemispheric average PS, gain and Mx means were 45.99+/−14.24 degrees, 0.62+/−0.38 cm/sec/mm Hg and 0.41+/− 0.13 respectively. Gain exhibited a difference by age (p=0.03). PS, gain and Mx values showed excellent inter-hemispheric correlation (r>0.8; p<0.001). PS and gain showed good reliability (R ICC=0.632, L ICC=0.576; p<0.001). PS and Mx showed fair correlation (r=−.37; p<0.001). Conclusions CA parameters obtained by time- and frequency-domain methods correlate well, and show good inter-hemispheric and test-retest reliability. Group means from healthy controls may provide adequate norms for determining abnormal CA in cerebrovascular patients.

Impaired Cerebral Autoregulation during Head Up Tilt in Patients with Severe Brain Injury

“…Further, the main purpose of including the control group was to compare postural changes in Mx and not for direct comparison of absolute values in the two groups. In addition, The Mx value is known to vary to some extent as a study by Ortega-Gutierez et al (2014) found variations between healthy subjects of similar magnitudes as ours [ 35 ].…”

Hypertension and Stroke in Patients with Left Ventricular Assist Devices (LVADs)

“…In this study, investigators found that changes in TCD were similar in patients with LVADs and controls arguing against the loss of cerebral auto-regulation [27•]. Other more advanced measures of cerebral auto-regulation, such as direct cerebral auto-regulation with a hypotensive or post-occlusive hyperemic challenge [28], have not been established in this patient population. Lastly, little data is known on whether arteriolar degenerative processes, such as accumulation of αβ-amyloid in cerebral amyloid angiopathy among those older than 55, interacts with blood pressure to increase the risk of ischemic or hemorrhagic stroke as it does in non-LVAD patients [29].…”

Cerebral autoregulation, beta amyloid, and white matter hyperintensities are interrelated

“…Transcranial Doppler ultrasongraphy combined with continuous blood pressure monitoring were used to evaluate DCA, as has been described previously [31,33]. Briefly, cerebral blood flow velocities (CBFV) were assessed using TCD (DWL-Multidop-X, Sipplingen, Germany).…”