Waves and Windkessels reviewed

Nicolaas Westerhof; Berend E. Westerhof

doi:10.1016/j.artres.2017.03.001

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Volume 18, Issue C, June 2017, Pages 102 - 111

Waves and Windkessels reviewed

Authors

Nicolaas Westerhof^a^{, *}, Berend E. Westerhof^a^{, b}

^aDepartment of Pulmonary Diseases, ICaR-VU, VU University Medical Center, Amsterdam, The Netherlands

^bLaboratory for Clinical Cardiovascular Physiology, Center for Heart Failure Research, Academic Medical Center, Amsterdam, The Netherlands

^*Corresponding author. Department of Pulmonary Diseases, Institute for Cardiovascular Research (ICaR-VU), VU University Medical Center, De Boelelaan 1117, 1081 HV Amsterdam, The Netherlands. E-mail address: n.westerhof@vumc.nl (N. Westerhof).

Corresponding Author

Nicolaas Westerhof

Available Online 31 March 2017.

DOI: 10.1016/j.artres.2017.03.001 How to use a DOI?
Keywords: Haemodynamics; Wave reflection; Wave intensity; Wave separation; iFR
Abstract: Pressure and flow are travelling waves and are reflected at many locations. The forward and reflected waves, obtained by wave separation, are compound waves. This compounded character of the reflected wave explains why its magnitude decreases with increased peripheral resistance, why it appears to run forward rather than backward, and why its return time relates poorly with aortic wave speed. A single tube (aorta) with distal reflection is therefore an incorrect arterial model. Wave Intensity Analysis (WIA) uses time derivatives of pressure and flow, augmenting rapid changes and incorrectly suggesting a ‘wave free period’ in diastole. Assuming a ‘wave free period’, the Reservoir-Wave Approach (RWA) separates pressure into a ‘waveless’ reservoir pressure, predicted by Frank’s Windkessel, and excess pressure, accounting for wave phenomena. However, the reservoir pressure, being twice the backward pressure, and location dependent, is a wave. The Instantaneous wave Free pressure Ratio distal and proximal of a stenosis, iFR, also assumes a ‘wave free period’, and is based on an instantaneous pressure-flow ratio, an incorrect resistance measure since Ohm’s law pertains to averaged pressure and flow only. Moreover, this ratio, while assumed minimal, was shown to decrease with vasodilation.

Windkessel models are descriptions of an arterial system at a single location using a limited number of parameters. Windkessels can be used as model but the actual arterial system is not a Windkessel. Total Peripheral Resistance and Total Arterial Compliance, (the 2-element, Frank Windkessel), supplemented with aortic characteristic impedance (3-element Windkessel) mimics the arterial system well.
Open Access: This is an open access article distributed under the CC BY-NC license.

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<Previous Article In Issue

Journal: Artery Research
Volume-Issue: 18 - C
Pages: 102 - 111
Publication Date: 2017/03/31
ISSN (Online): 1876-4401
ISSN (Print): 1872-9312
DOI: 10.1016/j.artres.2017.03.001 How to use a DOI?
Open Access: This is an open access article distributed under the CC BY-NC license.

Cite this article

ris enw bib

TY  - JOUR
AU  - Nicolaas Westerhof
AU  - Berend E. Westerhof
PY  - 2017
DA  - 2017/03/31
TI  - Waves and Windkessels reviewed
JO  - Artery Research
SP  - 102
EP  - 111
VL  - 18
IS  - C
SN  - 1876-4401
UR  - https://doi.org/10.1016/j.artres.2017.03.001
DO  - 10.1016/j.artres.2017.03.001
ID  - Westerhof2017
ER  -

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