Accurate Prediction of Wall Shear Stress in a Stented Artery: Newtonian Versus Non-Newtonian Models

2011 ◽  
Vol 133 (7) ◽  
Author(s):  
Juan Mejia ◽  
Rosaire Mongrain ◽  
Olivier F. Bertrand
Keyword(s):  
Shear Stress ◽  
Wall Shear Stress ◽  
Linear Model ◽  
Newtonian Fluid ◽  
Nonlinear Model ◽  
Numerical Models ◽  
Neointimal Hyperplasia ◽  
Computational Cost ◽  
Arterial Segment ◽  
Wall Shear

A significant amount of evidence linking wall shear stress to neointimal hyperplasia has been reported in the literature. As a result, numerical and experimental models have been created to study the influence of stent design on wall shear stress. Traditionally, blood has been assumed to behave as a Newtonian fluid, but recently that assumption has been challenged. The use of a linear model; however, can reduce computational cost, and allow the use of Newtonian fluids (e.g., glycerine and water) instead of a blood analog fluid in an experimental setup. Therefore, it is of interest whether a linear model can be used to accurately predict the wall shear stress caused by a non-Newtonian fluid such as blood within a stented arterial segment. The present work compares the resulting wall shear stress obtained using two linear and one nonlinear model under the same flow waveform. All numerical models are fully three-dimensional, transient, and incorporate a realistic stent geometry. It is shown that traditional linear models (based on blood’s lowest viscosity limit, 3.5 Pa s) underestimate the wall shear stress within a stented arterial segment, which can lead to an overestimation of the risk of restenosis. The second linear model, which uses a characteristic viscosity (based on an average strain rate, 4.7 Pa s), results in higher wall shear stress levels, but which are still substantially below those of the nonlinear model. It is therefore shown that nonlinear models result in more accurate predictions of wall shear stress within a stented arterial segment.

scholarly journals Alagebrium inhibits neointimal hyperplasia and restores distributions of wall shear stress by reducing downstream vascular resistance in obese and diabetic rats

2015 ◽  
Vol 309 (7) ◽  
pp. H1130-H1140 ◽  
Author(s):  
Hongfeng Wang ◽  
Dorothee Weihrauch ◽  
Judy R. Kersten ◽  
Jeffrey M. Toth ◽  
Anthony G. Passerini ◽  
...  
Keyword(s):  
Shear Stress ◽  
Wall Shear Stress ◽  
Vascular Resistance ◽  
Transforming Growth Factor ◽  
Oxidized Ldl ◽  
Neointimal Hyperplasia ◽  
Ldl Receptor ◽  
Transforming Growth Factor Β ◽  
Age Related ◽  
Wall Shear

Mechanisms of restenosis in type 2 diabetes mellitus (T2DM) are incompletely elucidated, but advanced glycation end-product (AGE)-induced vascular remodeling likely contributes. We tested the hypothesis that AGE-related collagen cross-linking (ARCC) leads to increased downstream vascular resistance and altered in-stent hemodynamics, thereby promoting neointimal hyperplasia (NH) in T2DM. We proposed that decreasing ARCC with ALT-711 (Alagebrium) would mitigate this response. Abdominal aortic stents were implanted in Zucker lean (ZL), obese (ZO), and diabetic (ZD) rats. Blood flow, vessel diameter, and wall shear stress (WSS) were calculated after 21 days, and NH was quantified. Arterial segments (aorta, carotid, iliac, femoral, and arterioles) were harvested to detect ARCC and protein expression, including transforming growth factor-β (TGF-β) and receptor for AGEs (RAGE). Downstream resistance was elevated (60%), whereas flow and WSS were significantly decreased (44% and 56%) in ZD vs. ZL rats. NH was increased in ZO but not ZD rats. ALT-711 reduced ARCC and resistance (46%) in ZD rats while decreasing NH and producing similar in-stent WSS across groups. No consistent differences in RAGE or TGF-β expression were observed in arterial segments. ALT-711 modified lectin-type oxidized LDL receptor 1 but not RAGE expression by cells on decellularized matrices. In conclusion, ALT-711 decreased ARCC, increased in-stent flow rate, and reduced NH in ZO and ZD rats through RAGE-independent pathways. The study supports an important role for AGE-induced remodeling within and downstream of stent implantation to promote enhanced NH in T2DM.

scholarly journals Modeling Blood Pulsatile Turbulent Flow in Stenotic Coronary Arteries

2020 ◽  
Vol 14 ◽  
Keyword(s):  
Blood Flow ◽  
Shear Stress ◽  
Wall Shear Stress ◽  
Turbulent Flow ◽  
Newtonian Fluid ◽  
Coronary Arteries ◽  
Pathological Condition ◽  
Flow Behavior ◽  
Wall Shear ◽  
Stenotic Arteries

Atherosclerosis is a potentially serious illness where arteries become clogged with fatty substances called plaques. Over the years, this pathological condition has been deeply studied and computational fluid dynamics has played an important role in investigating the blood flow behavior. Commonly, the blood flow is assumed to be laminar and a Newtonian fluid. However, under a stenotic condition, the blood behaves as a non-Newtonian fluid and the pulsatile blood flow through coronary arteries could result in a transition from laminar to turbulent flow condition. The present study aims to analyze and compare numerically the blood flow behavior, applying the k-ω SST model and a laminar assumption. The effects of Newtonian and non-Newtonian (Carreau) models were also studied. In addition, the effect of the stenosis degree on velocity fields and wall shear stress based descriptors were evaluated. According to the results, the turbulent model is shown to give a better overall representation of pulsatile flow in stenotic arteries. Regarding, the effect of non-Newtonian modeling, it was found to be more significant in wall shear stress measurements than in velocity profiles. In addition, the appearance of recirculation zones in the 50% stenotic model was observed during systole, and a low TAWSS and high OSI were detected downstream of the stenosis which, in turn, are risk factors for plaque formation. Finally, the turbulence intensity measurements allowed to distinguish regions of recirculating and disturbed flow.

A 3D-LDA Study of the Relation Between Wall Shear Stress and Intimal Thickness in a Human Aortic Bifurcation

1996 ◽  
Vol 118 (3) ◽  
pp. 273-279 ◽  
Author(s):  
Kozaburo Hayashi ◽  
Yutaka Yanai ◽  
Takeru Naiki
Keyword(s):  
Shear Stress ◽  
Wall Shear Stress ◽  
Blood Vessel ◽  
Newtonian Fluid ◽  
Shear Stresses ◽  
Elastic Model ◽  
Aortic Bifurcation ◽  
Local Flow ◽  
Intimal Thickness ◽  
Wall Shear

A realistic model experiment on hemodynamics was performed to study correlations between wall shear stresses measured in a cast model of the aortic bifurcation and intimal thickness at each corresponding site of the native blood vessel from which the cast had been made. An elastic model of a 54 year old human aortic bifurcation was made of a polyurethane elastomer using a dipping method, and was perfused with Newtonian or non-Newtonian fluid under physiologic pulsatile flow condition. Local flow velocities were measured with an optical-fibered, 3-dimensional laser Doppler anemometer (3D-LDA) to determine wall shear stresses. Distribution of intimal thickness was determined using histological specimens of the native blood vessel. The results obtained are: 1) Non-Newtonian fluid rheology increased wall shear stresses; 2) Positive correlations were observed between intimal thickness and the maximum instantaneous wall shear stress, and 3) However, if we take only the data from the circumference at the level of the flow divider tip, there were negative correlations between them.

scholarly journals Augmentation of Wall Shear Stress Inhibits Neointimal Hyperplasia After Stent Implantation

Circulation ◽  
2003 ◽  
Vol 107 (21) ◽  
pp. 2741-2746 ◽  
Author(s):  
Stéphane G. Carlier ◽  
Luc C.A. van Damme ◽  
Casper P. Blommerde ◽  
Jolanda J. Wentzel ◽  
Glenn van Langehove ◽  
...  
Keyword(s):  
Shear Stress ◽  
Wall Shear Stress ◽  
Stent Implantation ◽  
Neointimal Hyperplasia ◽  
Wall Shear

EFFECTS OF HEMATOCRIT LEVEL ON THE BLOOD FLOW IN THE CORRUGATED VESSEL DUE TO THE IMPLANTATION OF INTRAVASCULAR STENTS

2006 ◽  
Vol 18 (02) ◽  
pp. 80-86 ◽  
Author(s):  
TA-WEI DAVID TING ◽  
BING-SHIUN WU
Keyword(s):  
Blood Flow ◽  
Shear Stress ◽  
Stress Distribution ◽  
Wall Shear Stress ◽  
Newtonian Fluid ◽  
Shear Stress Distribution ◽  
Hematocrit Level ◽  
Wall Shear Stress Distribution ◽  
Atheroma Plaque ◽  
Wall Shear

The vascular stenting has been accepted as a very effective treatment of occlusive vascular disease. But the implantation of vascular stent will change the geometric shape of stenosed vessel to be corrugated and create some local hemodynamic features characterized by the flow separation, recirculation in the area close to the stent. Under the physiological conditions of left coronary artery and specific geometric shapes created by the implantation of stent, the numerical method has been used to solve the blood flow and the shear stress distribution patterns in the vicinity of the stent. The non-Newtonian fluids with different levels of hematocrit (H), 25%, 45%, 65% are employed for the numerical simulation and compared with the numerical results of the Newtonian fluid in which the blood viscosity is assumed to be constant. The simulations have revealed that the surface of stent and atheroma bumps experience lower time-averaged wall shear stress by the non-Newtonian fluid with lower level of hematocrit. The value of wall shear stress on the peak of atheroma bumps has also been studied because it may associate with the cause the rupture of atheroma plaque. The numerical results of Newtonian fluid were compared with those of non-Newtonian fluid with hematocrit level of 45%, the average hematocrit value inherent in normal person. It is noted that non-Newtonian effect on the time-averaged wall shear stress distribution along the stent surface is not significant. The outline of bulged atheroma experiences almost same time-averaged shear stress distribution acting by the fluid with or without the non-Newtonian property. It means that for the non-Newtonian fluid with hematocrit level of 45% the property of changing viscosity in the flow field didn't affect the results of wall shear stress distribution on the surfaces of stent and atheroma bump resulted from the simulation of Newtonian fluid flow. These results will provide insight into the effects of different levels of hematocrit on the blood flow in the corrugated vessel due to the implantation of stent. Our findings suggest that the level of hematocrit is closely associated with the value of wall shear stress distribution. It is particularly significant to acute stage of atherogenesis, intimal hyperplasia, platelet deposition, thrombosis, endothelial cell orientation and the rupture of atheroma plaque after the implantation of stent. Some of the results presented can be used to explain the clinical performance of vascular stenting.

Numerical Simulation of Fluid-Induced Vibration and Wall Shear Stress in Fusi/Form Cerebral Aneurysm: Newtonian and Non-Newtonian Fluid

2006 ◽  
Author(s):  
Yong Hyun Kim ◽  
Joon Sand Lee ◽  
Xin Wu
Keyword(s):  
Blood Flow ◽  
Shear Stress ◽  
Wall Shear Stress ◽  
Newtonian Fluid ◽  
Stress Gradient ◽  
In Vivo Studies ◽  
Rupture Area ◽  
Study Results ◽  
Wall Shear

Vascular techniques have been used for curing the aneurysm, but the reason for the occurrence of aneurysms can not be known using these techniques. These techniques are usually used for preventing a significant situation such as rupture of an aneurysm. In our study, blood flow effects with or without vascular techniques inside an aneurysm were analyzed with computational fluid dynamics (CFD). Important hemodynamic quantities like wall shear stress and pressure in vessel are difficult to measure in-vivo. Blood flow is assumed to be Newtonian fluid. But it actually consists of platelets, so it is also considered a non-Newtonian fluid in this study. Results of the numerical model were used to compare and analyze fluid characteristics with experimental data. Using the flow characteristics (wall shear stress (WSS), wall shear stress gradient (WSSG)), the rupture area was identified to be located in the distal area. However, the rupture area, in vivo studies, was observed to be present at a different location. During pulsatile flow, vibration induced by flow is implicated by weakening of the artery wall and affects more than shear stress. After adapting the fluid-induced vibration, the rupture area in aneurysm is found to be located in the same area as the in-vivo result. Since smaller inflow and low WSS provide the effect of the distal neck, the vibration provides more effects in dome area. In this study it has been found that the effect of shear stress on the rupture of aneurysm is less than the effect of vibration. In the case of non-Newtonian fluid, vibration induced by flow also has more effects than WSS and WSSG. The simulation results gave detailed information about hemodynamics under physiological pulsatile inlet condition.

Sequential Structural and Fluid Dynamic Numerical Simulations of a Stented Bifurcated Coronary Artery

2011 ◽  
Vol 133 (12) ◽  
Author(s):  
Stefano Morlacchi ◽  
Claudio Chiastra ◽  
Dario Gastaldi ◽  
Giancarlo Pennati ◽  
Gabriele Dubini ◽  
...  
Keyword(s):  
Shear Stress ◽  
Wall Shear Stress ◽  
Arterial Wall ◽  
Numerical Models ◽  
Fluid Dynamic ◽  
Side Branch ◽  
Mechanical Stresses ◽  
Shear Stresses ◽  
Sequential Approach ◽  
Wall Shear

Despite their success, stenting procedures are still associated to some clinical problems like sub-acute thrombosis and in-stent restenosis. Several clinical studies associate these phenomena to a combination of both structural and hemodynamic alterations caused by stent implantation. Recently, numerical models have been widely used in the literature to investigate stenting procedures but always from either a purely structural or fluid dynamic point of view. The aim of this work is the implementation of sequential structural and fluid dynamic numerical models to provide a better understanding of stenting procedures in coronary bifurcations. In particular, the realistic geometrical configurations obtained with structural simulations were used to create the fluid domains employed within transient fluid dynamic analyses. This sequential approach was applied to investigate the final kissing balloon (FKB) inflation during the provisional side branch technique. Mechanical stresses in the arterial wall and the stent as well as wall shear stresses along the arterial wall were examined before and after the FKB deployment. FKB provoked average mechanical stresses in the arterial wall almost 2.5 times higher with respect to those induced by inflation of the stent in the main branch only. Results also enlightened FKB benefits in terms of improved local blood flow pattern for the side branch access. As a drawback, the FKB generates a larger region of low wall shear stress. In particular, after FKB the percentage of area characterized by wall shear stresses lower than 0.5 Pa was 79.0%, while before the FKB it was 62.3%. For these reasons, a new tapered balloon dedicated to bifurcations was proposed. The inclusion of the modified balloon has reduced the mechanical stresses in the proximal arterial vessel to 40% and the low wall shear stress coverage area to 71.3%. In conclusion, these results show the relevance of the adopted sequential approach to study the wall mechanics and the hemodynamics created by stent deployment.

A Novel Computational Approach for Modeling Stent Reconstructing of an Aortic Bifurcation

2006 ◽  
Author(s):  
Ross Miller ◽  
Francine Battaglia
Keyword(s):  
Fluid Dynamics ◽  
Shear Stress ◽  
Wall Shear Stress ◽  
Numerical Models ◽  
Three Dimensional ◽  
Computational Approach ◽  
Aortic Bifurcation ◽  
Flow Phenomena ◽  
Novel Method ◽  
Wall Shear

Stent reconstruction of the aorta-iliac bifurcation was studied using computational fluid dynamics. Stents were modeled using a novel method, whereby the stents were represented as porous media. Three-dimensional numerical simulations using FLUENT were performed to determine how stent orientation affects the fluid dynamics. Three cases were studied and compared for both iliacs unstented, one iliac stented, and both iliacs stented. The stents lowered wall shear stress along the stented artery walls as compared to the unstented aorta-iliac model. However, the stent presence elevated vorticity, both in magnitude and size of the region. Additional studies were conducted to determine the effects for stent mis-alignment, where one stent protruded more into the aorta. It was found that when the stents were misaligned, wall shear stress increased near the stent inlet for the stent further inserted into the iliac. The resulting flow phenomena were consistent with other numerical models and medical investigations of stent reconstruction.

A cohort study showing correspondence of low wall shear stress and cephalic arch stenosis in brachiocephalic arteriovenous fistula access

2020 ◽  
pp. 112972982094204
Author(s):  
Mary Hammes ◽  
Kevin Cassel ◽  
Michael Boghosian ◽  
Sydeaka Watson ◽  
Brian Funaki ◽  
...  
Keyword(s):  
Shear Stress ◽  
Cohort Study ◽  
Wall Shear Stress ◽  
Arteriovenous Fistula ◽  
Neointimal Hyperplasia ◽  
Age Group ◽  
Wall Shear ◽  
The Relationship ◽  
Fistula Maturation ◽  
Brachiocephalic Fistula

Background: A brachiocephalic fistula is frequently placed for hemodialysis; unfortunately, cephalic arch stenosis commonly develops, leading to failure. We hypothesized that a contribution to brachiocephalic fistula failure is low wall shear stress resulting in neointimal hyperplasia leading to venous stenosis. The objective of this investigation is to determine correspondence of low wall shear stress and the development of cephalic arch stenosis. Methods: Forty subjects receiving hemodialysis with a primary brachiocephalic fistula access were followed from time of placement for 3 years or until cephalic arch stenosis. Venogram, Doppler, and viscosity were performed at time of fistula maturation, annually for 3 years or to time of cephalic arch stenosis. Computational hemodynamics modeling was performed to determine location and percent low wall shear stress in the arch. The relationship between wall shear stress at time of maturation and location of cephalic arch stenosis were estimated by correlating computational modeling and quadrant location of cephalic arch stenosis. Results: In total, 32 subjects developed cephalic arch stenosis with 26 displaying correspondence between location of low wall shear stress at time of maturation and subsequent cephalic arch stenosis, whereas 6 subjects did not (p = 0.0015). Most subjects with correspondence had low wall shear stress areas evident in greater than 20% of the arch (p = 0.0006). Low wall shear stress was associated with a higher risk of cephalic arch stenosis in the 23-to-45 age group (p = 0.0029). Conclusions: The presence and magnitude of low wall shear stress in the cephalic arch is a factor associated with development of cephalic arch stenosis in patients with brachiocephalic fistula. Attenuation of low wall shear stress at time of maturation may help prevent the development of cephalic arch stenosis which is difficult to treat once it develops.

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