A viscoelastic model of arterial wall motion in pulsatile flow: Implications for Doppler ultrasound clutter assessment

ArticleinPhysiological Measurement 29(2):157-79 · March 2008with29 Reads
DOI: 10.1088/0967-3334/29/2/001 · Source: PubMed
Abstract
The existing computational model studies of pulsatile blood flow in arteries have assumed either rigid wall characteristics or elastic arterial wall behavior with wall movement limited to the radial direction. Recent in vivo studies have identified significant viscoelastic wall properties and longitudinal wall displacements over the cardiac cycle. Determining the nature of these movements is important for predicting the effects of ultrasound clutter in Doppler ultrasound measurements. It is also important for developing an improved understanding of the physiology of vessel wall motion. We present an analytically-based computational model based on the Womersley equations for pulsatile blood flow within elastic and viscoelastic arteries. By comparison with published in vivo data of the human common carotid artery as well as uncertainty and sensitivity analyses, it is found that the predicted waveforms are in reasonable quantitative agreement. Either a pressure, pressure gradient or volumetric flow rate waveform over a single cardiac cycle is used as an input. Outputs include the pressure, pressure gradient, radial and longitudinal fluid velocities and arterial wall displacements, volumetric flow rate and average longitudinal velocity. It is concluded that longitudinal wall displacements comparable to the radial displacements can be present and should be considered when studying the effects of tissue movement on Doppler ultrasound clutter.
    • "Because WSS acts along the arteries, an obvious hypothesis is that WSS is an important factor in the longitudinal displacement of the arterial wall. The mechanical events within the arterial wall under the forces of pulsatile flow are currently being studied using mathematical models and simulations (Buka c and Cani c 2013; Fukui et al. 2007, Hodis and Zamir 2008, 2011a, 2011b Warriner et al. 2008). The relation between WSS and the longitudinal displacement of the arterial wall has, however, not been addressed in vivo. "
    [Show abstract] [Hide abstract] ABSTRACT: The mechanisms underlying longitudinal displacements of the arterial wall, that is, displacements of the wall layers along the artery, and the resulting intramural shear strain remain largely unknown. We have already found that these displacements undergo profound changes in response to catecholamines. Wall shear stress, closely related to wall shear rate, represents the viscous drag exerted on the vessel wall by flowing blood. The aim of the work described here was to study possible relations between the wall shear rate and the longitudinal displacements. We investigated the carotid arteries of five anesthetized pigs in different hemodynamic situations using in-house developed non-invasive ultrasound techniques. The study protocol included administration of epinephrine, norepinephrine and β-blockade (metoprolol). No significant correlation between longitudinal displacement of the intima-media complex and wall shear rate was found. This result suggests that one or multiple pulsatile forces other than wall shear stress are also working along arteries, strongly influencing arterial wall behavior. Copyright © 2015 World Federation for Ultrasound in Medicine & Biology. Published by Elsevier Inc. All rights reserved.
    Article · Feb 2015
    • "(5)). Motivated by Ref. [36] , the percent energy dissipation was calculated from the difference between the loading and unloading curves normalized by the energy associated with loading. Briefly, energies associated with loading (W L ) and unloading (W U ) were calculated as "
    [Show abstract] [Hide abstract] ABSTRACT: The stiffness of central arteries, namely, the aorta and common carotids, is a fundamental determinant of cardiovascular function and disease risk. Loss of elastic fiber integrity is one of the primary contributors to increased arterial stiffening in hypertension, aging, and related conditions. Elastic fibers consist of an elastin core and associated glycoproteins, hence defects in any of these constituents can adversely affect wall mechanics. In this paper, we focused on the contributions to central arterial stiffness by fibulin-5, an elastin-associated glycoprotein involved in elastogenesis. Specifically, we compared, for the first time, the biaxial mechanical properties of four central arterial regions - the ascending aorta, descending thoracic aorta, infrarenal aorta, and common carotid artery - from male and female wild-type and fibulin-5 deficient mice. Results revealed that, independent of sex, all four regions in the mutant mice manifested a marked increase in structural stiffness, a marked decrease in elastic energy storage, and typically an increase in energy dissipation, with all differences being most dramatic in the ascending aorta. Given that the primary function of large arteries is to store elastic energy during systole and to return this energy during diastole to work on the blood, fibulin-5 deficiency results in a widespread diminishment of central artery function that can have significant effects on hemodynamics and cardiac function.
    Full-text · Article · Dec 2014
    • "Introduction. Recent developments in ultrasound Contour and Speckle Tracking methods make it now possible to measure in vivo radial and longitudinal arterial wall displacements [40] [13] [44] [41] [14] [1] [12] [36]. These measurements for the first time reveal that longitudinal displacement of the intima-media complex in healthy 2000 Mathematics Subject Classification. "
    [Show abstract] [Hide abstract] ABSTRACT: Recent in vivo studies, utilizing ultrasound contour and speckle tracking methods, have identified significant longitudinal displacements of the intima-media complex, and viscoelastic arterial wall properties over a cardiac cycle. Existing computational models that use thin structure approximations of arterial walls have so far been limited to models that capture only radial wall displacements. The purpose of this work is to present a simple fluid-struture interaction (FSI) model and a stable, partitioned numerical scheme, which capture both longitudinal and radial displacements, as well as viscoelastic arterial wall properties. To test the computational model, longitudinal displacement of the common carotid artery and of the stenosed coronary arteries were compared with experimental data found in literature, showing excellent agreement. We found that, unlike radial displacement, longitudinal displacement in stenotic lesions is highly dependent on the stenotic geometry. We also showed that longitudinal displacement in atherosclerotic arteries is smaller than in healthy arteries, which is in line with the recent in vivo measurements that associate plaque burden with reduced total longitudinal wall displacement. This work presents a first step in understanding the role of longitudinal displacement in physiology and pathophysiology of arterial wall mechanics using computer simulations.
    Article · Apr 2013
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