Multimodal pressure-flow method to assess dynamics of cerebral autoregulation in stroke and hypertension
Vera Novak,Albert C. Yang,Lukas Lepicovsky,Ary L. Goldberger,Lewis A. Lipsitz,Chung-Kang Peng +5 more
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In the stroke and hypertensive groups, the resulting BP-BFV phase shift was significantly smaller compared to the normotensive group, and a standard autoregulation index did not differentiate the groups.Abstract:
This study evaluated the effects of stroke on regulation of cerebral blood flow in response to fluctuations in systemic blood pressure (BP). The autoregulatory dynamics are difficult to assess because of the nonstationarity and nonlinearity of the component signals. We studied 15 normotensive, 20 hypertensive and 15 minor stroke subjects (48.0 ± 1.3 years). BP and blood flow velocities (BFV) from middle cerebral arteries (MCA) were measured during the Valsalva maneuver (VM) using transcranial Doppler ultrasound. A new technique, multimodal pressure-flow analysis (MMPF), was implemented to analyze these short, nonstationary signals. MMPF analysis decomposes complex BP and BFV signals into multiple empirical modes, representing their instantaneous frequency-amplitude modulation. The empirical mode corresponding to the VM BP profile was used to construct the continuous phase diagram and to identify the minimum and maximum values from the residual BP (BPR) and BFV (BFVR) signals. The BP-BFV phase shift was calculated as the difference between the phase corresponding to the BPR and BFVR minimum (maximum) values. BP-BFV phase shifts were significantly different between groups. In the normotensive group, the BFVR minimum and maximum preceded the BPR minimum and maximum, respectively, leading to large positive values of BP-BFV shifts. In the stroke and hypertensive groups, the resulting BP-BFV phase shift was significantly smaller compared to the normotensive group. A standard autoregulation index did not differentiate the groups. The MMPF method enables evaluation of autoregulatory dynamics based on instantaneous BP-BFV phase analysis. Regulation of BP-BFV dynamics is altered with hypertension and after stroke, rendering blood flow dependent on blood pressure.read more
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Journal ArticleDOI
Cerebral Autoregulation: An Overview of Current Concepts and Methodology with Special Focus on the Elderly:
Arenda H.E.A. van Beek,Jurgen A.H.R. Claassen,Marcel G. M. Olde Rikkert,René W. M. M. Jansen +3 more
TL;DR: Of the various dynamic assessments of CA, a single sit-to-stand procedure is a feasible and physiologic method in the elderly, and the collection of spontaneous beat- to-beat changes in BP and CBF allows estimation of CA using the technique of transfer function analysis.
Journal ArticleDOI
Transfer function analysis of dynamic cerebral autoregulation: A white paper from the International Cerebral Autoregulation Research Network.
TL;DR: The purpose of the present white paper is to improve standardisation of parameters and settings adopted for application of transfer function analysis in studies of dynamic cerebral autoregulation.
Journal ArticleDOI
Monitoring of Cerebrovascular Autoregulation: Facts, Myths, and Missing Links
TL;DR: Monitoring cerebral autoregulation can be used in a variety of clinical scenarios and may be helpful in delineating optimal therapeutic strategies and in establishing consensus between CPP-directed protocols and the Lund-concept.
Journal ArticleDOI
The relationship between blood pressure and cognitive function
Vera Novak,Ihab Hajjar +1 more
TL;DR: Questions remain about the role of antihypertensive therapies for long-term prevention of cognitive decline and the existing evidence supporting the roles of vascular factors in late-life cognitive decline.
Journal ArticleDOI
Cerebral Autoregulation in Stroke A Review of Transcranial Doppler Studies
Marcel J.H. Aries,Jan Willem J. Elting,Jacques De Keyser,Berry Kremer,Patrick C.A.J. Vroomen +4 more
TL;DR: Transcranial Doppler in combination with continuous blood pressure measurement offers a method with a high temporal resolution feasible for bedside evaluation of cerebral autoregulation in the stroke unit.
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