scholarly journals Studying the Impact of Wall Shear Stress on the Development and Performance of Electrochemically Active Biofilms

ChemPlusChem ◽  
2020 ◽  
Vol 85 (10) ◽  
pp. 2298-2307
Author(s):  
Christopher Moß ◽  
Niklas Jarmatz ◽  
Dave Hartig ◽  
Lukas Schnöing ◽  
Stephan Scholl ◽  
...  
Keyword(s):  
Shear Stress ◽  
Wall Shear Stress ◽  
Electrochemically Active ◽  
Wall Shear ◽  
And Performance ◽  
The Impact

P3588The synergistic effect of NIRS-detected lipid-rich plaque and 5 different multidirectional wall shear stress metrics on human coronary plaque growth

2019 ◽  
Vol 40 (Supplement_1) ◽  
Author(s):  
E M J Hartman ◽  
A M Kok ◽  
A Hoogendoorn ◽  
F J H Gijsen ◽  
A F W Steen ◽  
...  
Keyword(s):  
Shear Stress ◽  
Wall Shear Stress ◽  
Synergistic Effect ◽  
Coronary Arteries ◽  
Wall Thickness ◽  
Plaque Progression ◽  
Lipid Rich Plaque ◽  
Plaque Growth ◽  
Wall Shear ◽  
The Impact

Abstract Introduction Local wall shear stress (WSS) metrics, high local lipid levels (as detected by near-infrared spectroscopy (NIRS)), as well as systemic lipid levels, have been individually associated with atherosclerotic disease progression. However, a possible synergistic effect remains to be elucidated. This study is the first study to combine WSS metrics with NIRS-detected local lipid content to investigate a potential synergistic effect on plaque progression in human coronary arteries. Methods The IMPACT study is a prospective, single centre study investigating the relation between atherosclerotic plaque progression and WSS in human coronary arteries. Patients with ACS treated with PCI were included. At baseline and after 1-year follow-up, patients underwent near-infrared spectroscopy intravascular ultrasound (NIRS-IVUS) imaging and intravascular doppler flow measurements of at least one non-culprit coronary artery. After one month, a CT angiography was made. CT derived centreline combined with IVUS lumen contours resulted in a 3D reconstruction of the vessel. The following WSS metrics were computed using computational fluid dynamics applying the vessel specific invasive flow measurements: time-average wall shear stress (TAWSS), relative residence time (RRT), cross-flow index, oscillatory shear index and transverse wall shear stress. Low TAWSS is known as pro atherogenic, in contrast to all the other shear stress metrics, at which a high magnitude is pro-atherogenic. The arteries were divided into 1.5mm/45° sectors. Based on NIRS-IVUS, wall thickness change over time was determined and NIRS positive sectors detected. Furthermore, per vessel the shear stress was divided into tertiles (low, intermediate, high). To investigate the synergistic effect of local lipids on shear stress related plaque growth, wall thickness change over time was related to the different shear stress metrics comparing the NIRS-positive with the NIRS-negative sectors. Results 15 non-culprit coronary arteries from the first 14 patients were analyzed (age 62±10 years old and 92.9% male). A total of 2219 sectors were studied (5.2%, N=130, NIRS-positive) for wall thickness changes. After studying all five shear stress metrics, we found for TAWSS and RRT that presence of lipids, as detected by NIRS, amplified the effect of shear stress on plaque progression (see figure). Sectors presenting with lipid-rich plaque, compared to NIRS-negative sectors, showed more progression when they were exposed to low TAWSS (p=0.07) or high RRT (p=0.012) and more regression in sectors exposed to high TAWSS (p=0.10) or low RRT (p=0.06). Delta wall thickness vs shear stress Conclusion We presented the first preliminary results of the IMPACT study, showing the synergistic effect of lipid rich plaque and shear stress on plaque progression. Therefore, intravascular lipid-rich plaque (NIRS) assessment has added value to shear stress profiling for the prediction of plaque growth, leading to improved risk stratification. Acknowledgement/Funding ERC starting grant 310457

Analysis of Flow and Wall Shear Stress in Curvature Induced Dorsal Aneurysms: Effect of Arterial Curvature

2009 ◽  
Author(s):  
Arun Ramu ◽  
Guo-Xiang Wang
Keyword(s):  
Shear Stress ◽  
Wall Shear Stress ◽  
Fluid Dynamic ◽  
Cerebral Arteries ◽  
Cerebral Aneurysms ◽  
Morbidity Rate ◽  
Mortality And Morbidity ◽  
Wall Shear ◽  
Primary Velocity ◽  
The Impact

Intracranial aneurysms are abnormal enlargement in the walls of cerebral arteries. The rupture of aneurysms is the leading cause of subarachnoid hemorrhage (SAH), with a high mortality and morbidity rate. A majority of saccular cerebral aneurysms occur at sites of arterial bifurcations. However, a good percentage of aneurysms are curvature induced and are found along the cavernous arterial segment. The occurrence of such non branching aneurysms, clinically called dorsal aneurysms, can be related to the increased wall shear stress at the curved arteries. The rupture of aneurysms usually occurs at the dome region, which is subjected to reduced wall shear stress (wss) owing to low re-circulating flow. Hence it is important to understand the impact of arterial curvature on the WSS distribution along the dome of aneurysms. Previously, studies have not taken into account the aspect of low WSS along the dome region. In the present 3-d computational fluid dynamic approach, we investigate the impact of varying arterial curvature on spherical dorsal aneurysms. The primary velocity patterns, the WSS distribution along the dome of the aneurysm and the area of increased WSS have been quantified for steady flow conditions.

scholarly journals Impact of blood rheology on wall shear stress in a model of the middle cerebral artery

2013 ◽  
Vol 3 (2) ◽  
pp. 20120094 ◽  
Author(s):  
Miguel O. Bernabeu ◽  
Rupert W. Nash ◽  
Derek Groen ◽  
Hywel B. Carver ◽  
James Hetherington ◽  
...  
Keyword(s):  
Shear Stress ◽  
Wall Shear Stress ◽  
Middle Cerebral Artery ◽  
Cerebral Artery ◽  
Decomposition Analysis ◽  
Blood Rheology ◽  
Vascular Pathology ◽  
Newtonian Model ◽  
Wall Shear ◽  
The Impact

Perturbations to the homeostatic distribution of mechanical forces exerted by blood on the endothelial layer have been correlated with vascular pathologies, including intracranial aneurysms and atherosclerosis. Recent computational work suggests that, in order to correctly characterize such forces, the shear-thinning properties of blood must be taken into account. To the best of our knowledge, these findings have never been compared against experimentally observed pathological thresholds. In this work, we apply the three-band diagram (TBD) analysis due to Gizzi et al. (Gizzi et al. 2011 Three-band decomposition analysis of wall shear stress in pulsatile flows. Phys. Rev. E 83 , 031902. ( doi:10.1103/PhysRevE.83.031902 )) to assess the impact of the choice of blood rheology model on a computational model of the right middle cerebral artery. Our results show that, in the model under study, the differences between the wall shear stress predicted by a Newtonian model and the well-known Carreau–Yasuda generalized Newtonian model are only significant if the vascular pathology under study is associated with a pathological threshold in the range 0.94–1.56 Pa, where the results of the TBD analysis of the rheology models considered differs. Otherwise, we observe no significant differences.

Negative Correlation of Wall Thickness With Wall Blood Pressure in a Patient-Specific Atherosclerotic Coronary Artery: A Case Report

2012 ◽  
Author(s):  
Biyue Liu ◽  
Jie Zheng ◽  
Richard Bach ◽  
Dalin Tang
Keyword(s):  
Blood Pressure ◽  
Shear Stress ◽  
Wall Shear Stress ◽  
Wall Thickness ◽  
Patient Specific ◽  
Artery Wall ◽  
Atherosclerosis Progression ◽  
Wall Shear ◽  
Intensive Investigation ◽  
The Impact

There are two major hemodynamic stresses imposed at the blood-arterial wall interface by flowing blood: the wall shear stress (WSS) acting tangentially to the wall, and the wall pressure (WP) acting vertically to the wall. These forces influence the artery wall metabolism and correspond to the local modifications of artery wall thickness, composition, microarchitecture, and compliance [2]. The role of flow wall shear stress in atherosclerosis progression has been under intensive investigation [4], while the impact of local blood pressure on plaque progression has been under-studied.

The Impact of Hemorheology on Wall Shear Stress in a Separated and Reattached Flow Region

2013 ◽  
Author(s):  
Khaled J. Hammad
Keyword(s):  
Shear Stress ◽  
Wall Shear Stress ◽  
Yield Stress ◽  
Flow Region ◽  
Shear Thinning ◽  
Progression Rate ◽  
Vortex Center ◽  
Wall Shear ◽  
Separated And Reattached Flow ◽  
The Impact

Wall-bounded separating and reattaching flows are encountered in biological applications dealing with blood flows through arteries and prosthetic devices. Separated and reattached flow regions have been associated in the past with the most common arterial disease, atherosclerosis. Previous studies suggest that local wall shear stress (WSS) patterns affect the location and progression rate of atherosclerotic lesions. A parametric study is performed to investigate the influence of hemorheology on the wall shear stress distribution in a separated and reattached flow region. Recent hemorheological studies quantified and emphasized the yield stress and shear-thinning non-Newtonian characteristics of unadulterated human blood. Numerical solutions to the governing equations that account for yield stress and shear-thinning rheological effects are obtained. A low WSS region is observed around the flow reattachment point while a peak WSS always exists close to the vortex center. The yield shear-thinning hemorheological model always results in the highest observed peak WSS. The yield stress impact on WSS distribution is most pronounced in the case of severe restrictions to the flow.

scholarly journals THE IMPACT OF SPATIAL GRADIENT OF ENDOTHELIAL WALL SHEAR STRESS ON PLAQUE COMPOSITION AND DESTABILIZATION IN ADVANCED PLAQUES

2011 ◽  
Vol 57 (14) ◽  
pp. E1867
Author(s):  
Wang-Soo Lee ◽  
Sang-Wook Kim ◽  
Young-Mi Jo ◽  
Seung-Wook Kim ◽  
Keung-Chul Rho ◽  
...  
Keyword(s):  
Shear Stress ◽  
Wall Shear Stress ◽  
Spatial Gradient ◽  
Plaque Composition ◽  
Wall Shear ◽  
The Impact

Effects of Nasal Cavity and Pharyngeal Regions on Airflow Simulation and Particle Depositions in Lower Generations of the Airways

2016 ◽  
Author(s):  
Shahab Taherian ◽  
Hamid Rahai ◽  
Diego Aguilar
Keyword(s):  
Shear Stress ◽  
Wall Shear Stress ◽  
Nasal Cavity ◽  
High Velocity ◽  
Secondary Flows ◽  
Lower Airways ◽  
Wall Shear ◽  
Type 3 ◽  
The Impact

This study evaluates the impact of excluding various regions of the upper respiratory system on particle depositions in lower airways. Three types of models were investigated, Type 1 includes nasal cavity, pharyngeal regions, trachea, and lower generations, Type 2 includes pharyngeal regions, trachea and lower generations, and finally Type 3 includes just the trachea and lower generations. Results indicate increased mean velocity, turbulent kinetic energy, and wall shear stress in hypopharynx and trachea regions for Types 1 and 2 models. There are strong secondary flows within the trachea just before the lower generations in these models, moving high velocity toward the wall regions, resulting in large velocity gradients and thus increased wall shear stress. For Type 3 model, only a small region experiences high velocity secondary flow and its distribution is significantly different than those of Type 1 and 2. Although total particle depositions differ between models, results show that for fine particles, the deposition ratios in lower airways are nearly the same.

Angular Remodeling in Single Stent-Assisted Coiling Displaces and Attenuates the Flow Impingement Zone at the Neck of Intracranial Bifurcation Aneurysms

Neurosurgery ◽  
2013 ◽  
Vol 72 (5) ◽  
pp. 739-748 ◽  
Author(s):  
Bulang Gao ◽  
Merih I. Baharoglu ◽  
Adel M. Malek
Keyword(s):  
Shear Stress ◽  
Wall Shear Stress ◽  
Computational Fluid Dynamic ◽  
Fluid Dynamic ◽  
Bifurcation Angle ◽  
Impingement Zone ◽  
Wall Shear ◽  
And Migration ◽  
The Impact

Abstract BACKGROUND: Self-expanding intracranial stent-assisted coiling of bifurcation aneurysms has recently been shown to straighten target cerebral vessels, a phenomenon with unknown hemodynamic effect. OBJECTIVE: To investigate the impact of angular remodeling in aneurysms treated with single stent-assisted coiling with the use of computational fluid dynamic techniques. METHODS: Fourteen patients (7 women, mean age 55) who underwent stent coiling of 14 wide-necked bifurcation aneurysms were included based on the availability of high-resolution 3-dimensional rotational angiography. Pretreatment data sets underwent virtual aneurysm removal to isolate the effect of stenting. Wall shear stress and pressure profiles obtained from constant flow input computational fluid dynamic analysis were analyzed for apical hemodynamic changes. RESULTS: Stenting increased the bifurcation angle with significant straightening immediately after treatment and at follow-up (107.3° vs 144.9°, P < .001). The increased stented angle at follow-up led to decreased pressure drop at the bifurcation apex (12.2 vs 9.9 Pa, P < .003) and migration of the flow impingement zone (FIZ) toward the contralateral nonstented daughter branch by a mean of 1.48 ± 0.2 mm. Stent-induced angular remodeling decreased FIZ width separating peak apical wall shear stress (3.4 vs 2.5 mm, P < .004). Analysis of FIZ distance measured from the parent vessel centerline showed it to be linearly (r = .58, P < .002) and FIZ width inversely correlated (r = .46, P < .02) to vessel bifurcation angle. CONCLUSION: Stent-induced angular remodeling significantly altered bifurcation apex hemodynamics in a favorable direction by blunting apical pressure and inducing the narrowing and migration of the FIZ, a novel response to intracranial stenting that should be added to intimal hyperplasia and flow diversion.

scholarly journals An LDV based method to quantify the error of PC-MRI derived Wall Shear Stress measurement

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Marco Castagna ◽  
Sébastien Levilly ◽  
Perrine Paul-Gilloteaux ◽  
Saïd Moussaoui ◽  
Jean-Marc Rousset ◽  
...  
Keyword(s):  
Shear Stress ◽  
Wall Shear Stress ◽  
Stress Measurement ◽  
Computation Method ◽  
Velocity Data ◽  
4D Flow Mri ◽  
4D Flow ◽  
Flow Mri ◽  
Wall Shear ◽  
The Impact

AbstractWall Shear Stress (WSS) has been demonstrated to be a biomarker of the development of atherosclerosis. In vivo assessment of WSS is still challenging, but 4D Flow MRI represents a promising tool to provide 3D velocity data from which WSS can be calculated. In this study, a system based on Laser Doppler Velocimetry (LDV) was developed to validate new improvements of 4D Flow MRI acquisitions and derived WSS computing. A hydraulic circuit was manufactured to allow both 4D Flow MRI and LDV velocity measurements. WSS profiles were calculated with one 2D and one 3D method. Results indicated an excellent agreement between MRI and LDV velocity data, and thus the set-up enabled the evaluation of the improved performances of 3D with respect to the 2D-WSS computation method. To provide a concrete example of the efficacy of this method, the influence of the spatial resolution of MRI data on derived 3D-WSS profiles was investigated. This investigation showed that, with acquisition times compatible with standard clinical conditions, a refined MRI resolution does not improve WSS assessment, if the impact of noise is unreduced. This study represents a reliable basis to validate with LDV WSS calculation methods based on 4D Flow MRI.

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