scholarly journals Fluid-structure interaction simulation of tissue degradation and its effects on intra-aneurysm hemodynamics

2022 ◽  
Author(s):  
Haifeng Wang ◽  
Klemens Uhlmann ◽  
Vijay Vedula ◽  
Daniel Balzani ◽  
Fathollah Varnik
Keyword(s):  
Shear Stress ◽  
Wall Shear Stress ◽  
Vascular Diseases ◽  
Von Mises Stress ◽  
Arterial Walls ◽  
Tissue Degradation ◽  
Blood Pressures ◽  
Arterial Wall Mechanics ◽  
Wall Shear ◽  
Von Mises

AbstractTissue degradation plays a crucial role in vascular diseases such as atherosclerosis and aneurysms. Computational modeling of vascular hemodynamics incorporating both arterial wall mechanics and tissue degradation has been a challenging task. In this study, we propose a novel finite element method-based approach to model the microscopic degradation of arterial walls and its interaction with blood flow. The model is applied to study the combined effects of pulsatile flow and tissue degradation on the deformation and intra-aneurysm hemodynamics. Our computational analysis reveals that tissue degradation leads to a weakening of the aneurysmal wall, which manifests itself in a larger deformation and a smaller von Mises stress. Moreover, simulation results for different heart rates, blood pressures and aneurysm geometries indicate consistently that, upon tissue degradation, wall shear stress increases near the flow-impingement region and decreases away from it. These findings are discussed in the context of recent reports regarding the role of both high and low wall shear stress for the progression and rupture of aneurysms.

scholarly journals Fluid-structure interaction simulation of tissue degradation and its effects on intra-aneurysm hemodynamics

2021 ◽  
Author(s):  
Haifeng Wang ◽  
Klemens Uhlmann ◽  
Vijay Vedula ◽  
Daniel Balzani ◽  
Fathollah Varnik
Keyword(s):  
Shear Stress ◽  
Wall Shear Stress ◽  
Vascular Diseases ◽  
Von Mises Stress ◽  
Aneurysmal Wall ◽  
Tissue Degradation ◽  
Blood Pressures ◽  
Interaction Simulation ◽  
Wall Shear ◽  
Von Mises

Tissue degradation plays a crucial role in vascular diseases such as atherosclerosis and aneurysms. We present a novel finite element method-based approach to model the microscopic degradation of an aneurysmal wall due to its interaction with blood flow. The model is applied to study the combined effects of pulsatile flow and tissue degradation on the deformation and intra-aneurysm hemodynamics. Our computational analysis reveals that tissue degradation leads to a weakening of the aneurysmal wall, which manifests itself in a larger deformation and a smaller von Mises stress. Moreover, simulation results for different heart rates, blood pressures and aneurysm geometries indicate consistently that, upon tissue degradation, wall shear stress increases near the flow-impingement region and decreases away from it. These findings are discussed in the context of recent reports regarding the role of both high and low wall shear stress for the progression and rupture of aneurysms.

Influence of Intermittent Pneumatic Compression on Wall Shear Stress and Nitric Oxide Levels

2011 ◽  
Author(s):  
Ganesh Swaminathan ◽  
Suraj Thyagaraj ◽  
Francis Loth ◽  
Susan McCormick ◽  
Hisham Bassiouny
Keyword(s):  
Nitric Oxide ◽  
Shear Stress ◽  
Wall Shear Stress ◽  
Blood Vessels ◽  
Healthy Subjects ◽  
Vascular Diseases ◽  
Intermittent Pneumatic Compression ◽  
Peripheral Vascular ◽  
Peripheral Vascular Diseases ◽  
Wall Shear

Wall shear stress (WSS) in blood vessels has been shown to play an important role in the development of atherosclerosis. In particular, regions of low and oscillating WSS have been shown to correlate with the localization of atherosclerosis. Thus, we hypothesize that increasing the WSS for patients with peripheral vascular diseases (PVD) will either reduce PVD severity or slow its progression. We analyzed WSS changes from a study by Delis et al. on 32 limbs of PVD patients [1]. Results show that intermittent pneumatic compression (IPC) increases mean WSS by 170% and 240% in PVD patients and healthy subjects, respectively. Peak WSS was found to increase by 93% and 40% in PVD patients and healthy subjects, respectively. In addition, we examined changes in NOX level with use of IPC on five limbs from PVD patients. Our study demonstrated increased NOx levels in subjects after IPC. Further research is needed to determine the benefits of IPC for PVD patients.

Effect of Wall Shear Stress on Abdominal Aortic Aneurysm Expansion: Study With Longitudinal Patient Images

2012 ◽  
Author(s):  
B. Zambrano ◽  
A. Dupay ◽  
F. Jaberi ◽  
W. Lee ◽  
S. Baek
Keyword(s):  
Shear Stress ◽  
Wall Shear Stress ◽  
Open Surgery ◽  
Vascular Diseases ◽  
Aortic Aneurysms ◽  
Maximum Diameter ◽  
Abdominal Aortic ◽  
Reduce Risk ◽  
Wall Shear

Abdominal Aortic Aneurysms (AAA), a focal enlargement of abdominal aorta, is a form of vascular diseases that affects large part of the population. It can cause the mortality up to 90% of the cases when it ruptures. Currently, the best known treatment to reduce risk is open surgery or endovascular repair. Since the risk of such surgery repair is high, in most patients with AAAs< 55mm in its maximum diameter the surgical treatment is postponed. An effort to enhance the accuracy of the risk assessment and to prevent AAA’s growth and rupture is being made, but the mechanisms promoting AAAs growth are still largely unknown. AAAs can be affected by different factors, among those, hemodynamics is known to play important roles in AAA initiation and progression. Particularly, the wall shear stress is believed to contribute to AAA expansion and rupture. For the present study, we use geometries constructed from longitudinal CT images obtained during AAA follow-up studies and investigate relations between multiple hemodynamics factors with local expansion of AAAs.

Coronary Artery Stenting Affects Wall Shear Stress Topological Skeleton

2022 ◽  
Author(s):  
Claudio Chiastra ◽  
Valentina Mazzi ◽  
Maurizio Lodi Rizzini ◽  
Karol Calò ◽  
Anna Corti ◽  
...  
Keyword(s):  
Shear Stress ◽  
Coronary Artery ◽  
Wall Shear Stress ◽  
Vascular Diseases ◽  
Human Coronary Artery ◽  
Term Outcome ◽  
Clinical Images ◽  
Long Term Outcome ◽  
Wall Shear ◽  
The Impact

Abstract Despite the important advancements in the stent technology for the treatment of diseased coronary arteries, major complications still affect the post-operative long-term outcome. The stent-induced flow disturbances, and especially the altered wall shear stress (WSS) profile at the strut level, play an important role in the pathophysiological mechanisms leading to stent thrombosis (ST) and in-stent restenosis (ISR). In this context, the analysis of the WSS topological skeleton is gaining more and more interest by extending the current understanding of the association between local hemodynamics and vascular diseases. The present study aims to analyze the impact that a deployed coronary stent has on the WSS topological skeleton. Computational fluid dynamics simulations were performed in three stented human coronary artery geometries reconstructed from clinical images. The selected cases presented stents with different designs (i.e., two contemporary drug eluting stents and one bioresorbable scaffold) and included regions with stent malapposition or overlapping. A recently proposed Eulerian-based approach was applied to analyze the WSS topological skeleton features. The results highlighted that the presence of single or multiple stents within a coronary artery markedly impacts the WSS topological skeleton. In particular, repetitive patterns of WSS divergence were observed at the luminal surface, highlighting a WSS contraction action proximal to the struts and a WSS expansion action distal to the struts. This WSS action pattern was independent from the stent design. In conclusions, these findings could contribute to a deeper understanding of the hemodynamic-driven processes underlying ST and ISR.

scholarly journals NUMERICAL EVALUATION OF CURVATURE EFFECTS ON SHEAR STRESSES ACROSS ARTERIAL STENOSES

2002 ◽  
Vol 14 (04) ◽  
pp. 164-170 ◽  
Author(s):  
YANG-YAO NIU ◽  
WEI-KUANG CHU ◽  
LUNG-CHENG LEE ◽  
HSI-YU YU
Keyword(s):  
Shear Stress ◽  
Wall Shear Stress ◽  
Three Dimensional ◽  
Shear Stresses ◽  
Arterial Walls ◽  
Curvature Effects ◽  
Newtonian Flows ◽  
Flow Features ◽  
Wall Shear ◽  
Arterial Stenoses

In this study, Newtonian flows passing through three-dimensional curved and straight axissymmetrical stenotic tubes are investigated. The geometry effects and Reynolds numbers of 100, 200, 400, and 600 on the formation of the shear rate over arterial walls are studied. It is noted that geometric effects on flow features such as velocity profiles, pressure and wall shear stress distributions in the post-stenotic region are significant. The location of maximum wall shear stress is found to relate to the geometric effect much than the Reynolds number effect.

scholarly journals On the Potential Self-Amplification of Aneurysms Due to Tissue Degradation and Blood Flow Revealed From FSI Simulations

2021 ◽  
Vol 12 ◽  
Author(s):  
Haifeng Wang ◽  
Daniel Balzani ◽  
Vijay Vedula ◽  
Klemens Uhlmann ◽  
Fathollah Varnik
Keyword(s):  
Blood Flow ◽  
Shear Stress ◽  
Wall Shear Stress ◽  
Cell Activation ◽  
Hemodynamic Changes ◽  
Endothelial Cell Activation ◽  
Potential Index ◽  
Tissue Degradation ◽  
Wall Shear ◽  
Induced Changes

Tissue degradation plays a crucial role in the formation and rupture of aneurysms. Using numerical computer simulations, we study the combined effects of blood flow and tissue degradation on intra-aneurysm hemodynamics. Our computational analysis reveals that the degradation-induced changes of the time-averaged wall shear stress (TAWSS) and oscillatory shear index (OSI) within the aneurysm dome are inversely correlated. Importantly, their correlation is enhanced in the process of tissue degradation. Regions with a low TAWSS and a high OSI experience still lower TAWSS and higher OSI during degradation. Furthermore, we observed that degradation leads to an increase of the endothelial cell activation potential index, in particular, at places experiencing low wall shear stress. These findings are robust and occur for different geometries, degradation intensities, heart rates and pressures. We interpret these findings in the context of recent literature and argue that the degradation-induced hemodynamic changes may lead to a self-amplification of the flow-induced progressive damage of the aneurysmal wall.

Abstract 235: Integration of Patient-specific Computational Hemodynamics and Vessel Wall Shear Stress Into MRI Diagnosis of Vascular Diseases

2016 ◽  
Vol 119 (suppl_1) ◽  
Author(s):  
Huidan W Yu ◽  
Xi Chen ◽  
Zhiqiang Wang ◽  
Rou Chen ◽  
Chen Lin ◽  
...  
Keyword(s):  
Shear Stress ◽  
Wall Shear Stress ◽  
Carotid Arteries ◽  
Vascular Diseases ◽  
Patient Specific ◽  
Imaging Data ◽  
Mri Imaging ◽  
Measured Velocity ◽  
Tof Mra ◽  
Wall Shear

The research objective is to expand the capability of current MRI imaging technique in assessing the overall risk and predicted outcomes of atherosclerotic diseases through the quantification of individual patient-specific hemodynamics, including flow, pressure, and wall-shear stress. A unique computational modeling technique, named InVascular, is integrated directly into clinical MRI scanners as the extension of the image reconstruction and post-processing pipeline so that velocity, pressure, vorticity, and WSS can be available immediately with other diagnostic images. InVascular is a unified and GPU accelerated computation platform to model and simulate patient-specific hemodynamics and flow-vessel interaction based on MRI imaging data. In this study, we validate the efficiency and accuracy of InVascular through quantitative hemodynamics in vertebral and carotid arteries. A group of five volunteers participated in the scanning of high resolution time-of-flight (TOF) and low resolution electrocardiogram (ECG) gated phase contrast (PC) MR angiogram (MRA) images. For each case, InVascular successively processes the images to get vessel geometry from TOF MRA and velocity slices from PC MRA and solve the fluid dynamics inside the carotid arteries with PC MRA measured velocity at the inlet and outlet (Fig. 1 a-c). The velocity profiles from Invascular and PC MRA are compared at the same location (Fig. 1 d-g ). We conclude that integration of MRAs and InVascular can well captured the velocity fields as MRI measures. InVascular can provide quantitative pressure and WSS (Fig. 1h ) information as well.

scholarly journals Wall Shear Stress Topological Skeleton Analysis in Cardiovascular Flows: Methods and Applications

Mathematics ◽  
2021 ◽  
Vol 9 (7) ◽  
pp. 720
Author(s):  
Valentina Mazzi ◽  
Umberto Morbiducci ◽  
Karol Calò ◽  
Giuseppe De Nisco ◽  
Maurizio Lodi Rizzini ◽  
...  
Keyword(s):  
Shear Stress ◽  
Wall Shear Stress ◽  
Fixed Points ◽  
Vascular Diseases ◽  
Dynamical System Theory ◽  
Focal Points ◽  
Clinical Observations ◽  
Flow Disturbances ◽  
Wall Shear ◽  
Processing Techniques

A marked interest has recently emerged regarding the analysis of the wall shear stress (WSS) vector field topological skeleton in cardiovascular flows. Based on dynamical system theory, the WSS topological skeleton is composed of fixed points, i.e., focal points where WSS locally vanishes, and unstable/stable manifolds, consisting of contraction/expansion regions linking fixed points. Such an interest arises from its ability to reflect the presence of near-wall hemodynamic features associated with the onset and progression of vascular diseases. Over the years, Lagrangian-based and Eulerian-based post-processing techniques have been proposed aiming at identifying the topological skeleton features of the WSS. Here, the theoretical and methodological bases supporting the Lagrangian- and Eulerian-based methods currently used in the literature are reported and discussed, highlighting their application to cardiovascular flows. The final aim is to promote the use of WSS topological skeleton analysis in hemodynamic applications and to encourage its application in future mechanobiology studies in order to increase the chance of elucidating the mechanistic links between blood flow disturbances, vascular disease, and clinical observations.

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