Longitudinal Effect of Wall Shear Stress on the Amount of Intimal-Medial Thickening of Venous Wall in Arteriovenous Fistula

2012 ◽  
Author(s):  
Ehsan Rajabi-Jaghargh ◽  
Prabir Roy-Chaudhury ◽  
Mahesh K. Krishnamoorthy ◽  
Yang Wang ◽  
Rupak K. Banerjee
Keyword(s):  
Shear Stress ◽  
Wall Shear Stress ◽  
Arteriovenous Fistula ◽  
Hemodynamic Parameters ◽  
Temporal Gradient ◽  
Post Surgery ◽  
Venous Stenosis ◽  
Venous Diameter ◽  
Consistent Increase ◽  
Wall Shear

Arteriovenous fistula (AVF) maturation failure is mainly due to venous stenosis characterized by significant amount of intima-media thickening (IMT). Although hemodynamic endpoints are believed to play a crucial role in pathogenesis of venous stenosis, the exact mechanism behind this is unclear. Our hypothesis is that longitudinal (temporal) changes of hemodynamic parameters, specifically wall shear stress (WSS), influences amount of IMT in maturation process of AVF. AVFs were created in curved (C-AVF) and straight (S-AVF) configurations between femoral artery and vein of 3 pigs. CT-scans and ultrasound were utilized to calculate WSS at 2D (D: days), 7D, and 28D post-surgery. IMT was measured at 4 histological blocks along the vein of AVFs. It was found that C-AVF underwent outward remodeling characterized by consistent increase in venous diameter and larger IMT. This remodeling process was governed by negative temporal gradient of WSS (τ′) [−0.99 ± 0.60 dyn/cm2/day]. In contrast, S-AVF underwent inward remodeling characterized by temporal decrease in venous diameter and relatively smaller IMT. This remodeling process was governed by positive τ′ (0.42 ± 0.6 dyn/cm2/day). In summary, temporal gradient of WSS influences IMT. Temporal decrease of WSS in C-AVF resulted in vasodilation and outward growth of wall (favorable to maturation). However, temporal increase in WSS in S-AVF leaded to vasoconstriction and inward growth of wall (detrimental to maturation). Thus, clinically it can be of great importance to surgeons to create AVF in a configuration that can result in favorable hemodynamic parameters and histological end-points.

Sensitivity of Hemodynamic Parameters to Waveform, Flow Division, and Head Rotation in the Human Carotid Bifurcation

2008 ◽  
Author(s):  
Yannis Papaharilaou ◽  
Ioannis Seimenis ◽  
John Ekaterinaris ◽  
Georgios Georgiou ◽  
Eleni Eracleous ◽  
...  
Keyword(s):  
Shear Stress ◽  
Wall Shear Stress ◽  
Head Rotation ◽  
Carotid Bifurcation ◽  
Hemodynamic Parameters ◽  
Flow Waveform ◽  
Temporal Gradient ◽  
Wall Shear ◽  
Flow Division ◽  
Human Carotid

Hemodynamic parameters such as time averaged wall shear stress (TAWSS), wall shear stress temporal gradient (WSSTG) and Oscillatory Shear Index (OSI) have previously been cited as parameters associated with the development of atherosclerotic disease at the human carotid bifurcation [1,2]. The sensitivity of these important parameters however, with variations of driving flow waveform, flow division and posture changes are not well known. To investigate these changes, we have used image based CFD, to analyze the flowfield of the carotid bifurcation of a healthy volunteer for five different input waveforms, three flow division ratios and two head postures.

scholarly journals Hemodynamic parameters and vessel tortuosity: an investigation with a mesenterial vascular network

2017 ◽  
Vol 1 (4) ◽  
pp. 62-68
Author(s):  
Roberto Annunziata ◽  
Bettina Reglin ◽  
Axel Pries ◽  
Emanuele Trucco
Keyword(s):  
Shear Stress ◽  
Wall Shear Stress ◽  
Oxygen Saturation ◽  
Wall Thickness ◽  
Blood Velocity ◽  
Vascular Network ◽  
Hemodynamic Parameters ◽  
Vessel Tortuosity ◽  
Wall Shear ◽  
Quantitative Definition

Purpose: The effect of hemodynamic parameters on vessel tortuosity remains un-clear. Here we investigate the correlation of tortuosity with a set of hemodynamicparameters in a mesenterial vascular network.Methods: A mesenterial vascular network of 389 vessels (131 arteries, 132 veins, and 126 capillaries) was imaged. Eleven hemodynamic parameters were measured (pressure, wall shear stress, diameter, blood velocity and flow, viscosity, haematocrit, partial oxygen saturation, oxygen saturation, wall thickness, and local vessel density). Tortuosity was assessed quantitatively with a validated algorithm and correlation computed with subsets of hemodynamic parameters selected by a lasso regressor.Results: Results suggest that tortuosity is related to pressure, wall shear stress, diameter, blood velocity, viscosity, partial but not full oxygen saturation, and wall thickness for the arteries; diameter, blood flow, hematocrit, and density for the veins; and viscosity (but not hematocrit), partial and full oxygen saturation, and density for the capillaries. The combination of hemodynamic parameters correlating best with tortuosity is the set of all parameters except density (r = 0.64, p < 0.01), using as tortuosity definition the set of tortuosity features (geometric measures) correlating best with a single hemodynamic factor for the arteries.Conclusion: This pilot suggests two general conclusions. First, the quantitative definition of tortuosity (i.e., the set of geometric features adopted) should be tuned to the specific data and problem considered. Second, tortuosity is caused by a combination of hemodynamic factors, not a single one.

A Review On the Effect of Temporal Geometric Variations of the Coronary Arteries On the Wall Shear Stress and Pressure Drop

2021 ◽  
Author(s):  
Navid Freidoonimehr ◽  
Rey Chin ◽  
Anthony C. Zander ◽  
Maziar Arjomandi
Keyword(s):  
Shear Stress ◽  
Pressure Drop ◽  
Wall Shear Stress ◽  
Coronary Arteries ◽  
Cardiac Cycle ◽  
Temporal Variations ◽  
Hemodynamic Parameters ◽  
Clinical Environment ◽  
Cross Sectional ◽  
Wall Shear

Abstract Temporal variations of the coronary arteries during a cardiac cycle are defined as the superposition of the changes in the position, curvature, and torsion of the coronary artery axis markers and the variations in the lumen cross-sectional shape due to the distensible wall motion induced by the pulse pressure and contraction of the myocardium in a cardiac cycle. This review discusses whether the modelling the temporal variations of the coronary arteries is needed for the investigation of the hemodynamics specifically in time critical applications such as a clinical environment. The numerical modellings in the literature which model or disregard the temporal variations of the coronary arteries on the hemodynamic parameters are discussed. The results in the literature show that neglecting the effects of temporal geometric variations is expected to result in about 5\% deviation of the time-averaged pressure drop and wall shear stress values and also about 20\% deviation of the temporal variations of hemodynamic parameters, such as time-dependent wall shear stress and oscillatory shear index. This review study can be considered as a guide for the future studies to outline the conditions in which temporal variations of the coronary arteries can be neglected, while providing a reliable estimation of hemodynamic parameters.

scholarly journals Wall Shear Stress Measurement Using Phase Contrast Magnetic Resonance Imaging with Phase Contrast Magnetic Resonance Angiography in Arteriovenous Polytetrafluoroethylene Grafts

Angiology ◽  
2009 ◽  
Vol 60 (4) ◽  
pp. 441-447 ◽  
Author(s):  
Sanjay Misra ◽  
Alex A. Fu ◽  
Khamal D. Misra ◽  
James F. Glockner ◽  
Debabrata Mukhopadhyay
Keyword(s):  
Magnetic Resonance Imaging ◽  
Shear Stress ◽  
Magnetic Resonance ◽  
Wall Shear Stress ◽  
Phase Contrast ◽  
Resonance Imaging ◽  
Phase Contrast Magnetic Resonance ◽  
Venous Stenosis ◽  
Contrast Magnetic Resonance ◽  
Wall Shear

Purpose The purpose of the present article was to determine the changes in luminal vessel area, blood flow, and wall shear stress in both the inflow artery and the venous stenosis of arteriovenous polytetrafluoroethylene (PTFE) grafts. Methods and materials Polytetrafluoroethylene grafts were placed from the carotid artery to the ipsilateral jugular vein in 8 castrated juvenile male pigs. Contrast-enhanced magnetic resonance angiography (MRA) with cine phase-contrast magnetic resonance imaging (MRI) was performed 2 weeks after graft placement. Results The mean wall shear stress at the venous stenosis was 4 times higher than the control vein, while the inflow artery was only 2-fold higher. By day 14, venous stenosis had formed, which was characterized by narrowed area and elevated blood flow. Conclusion By day 14, there is venous stenosis formation in porcine arteriovenous PTFE grafts with increased shear stress with decreased area when compared to control vein.

scholarly journals Developing Pulsatile Flow in a Deployed Coronary Stent

2005 ◽  
Vol 128 (3) ◽  
pp. 347-359 ◽  
Author(s):  
Divakar Rajamohan ◽  
Rupak K. Banerjee ◽  
Lloyd H. Back ◽  
Ashraf A. Ibrahim ◽  
Milind A. Jog
Keyword(s):  
Shear Stress ◽  
Wall Shear Stress ◽  
Pulsatile Flow ◽  
Thrombus Formation ◽  
Three Dimensional ◽  
Tissue Growth ◽  
Coronary Stent ◽  
Stress Distributions ◽  
Hemodynamic Parameters ◽  
Wall Shear

A major consequence of stent implantation is restenosis that occurs due to neointimal formation. This patho-physiologic process of tissue growth may not be completely eliminated. Recent evidence suggests that there are several factors such as geometry and size of vessel, and stent design that alter hemodynamic parameters, including local wall shear stress distributions, all of which influence the restenosis process. The present three-dimensional analysis of developing pulsatile flow in a deployed coronary stent quantifies hemodynamic parameters and illustrates the changes in local wall shear stress distributions and their impact on restenosis. The present model evaluates the effect of entrance flow, where the stent is placed at the entrance region of a branched coronary artery. Stent geometry showed a complex three-dimensional variation of wall shear stress distributions within the stented region. Higher order of magnitude of wall shear stress of 530dyn∕cm2 is observed on the surface of cross-link intersections at the entrance of the stent. A low positive wall shear stress of 10dyn∕cm2 and a negative wall shear stress of −10dyn∕cm2 are seen at the immediate upstream and downstream regions of strut intersections, respectively. Modified oscillatory shear index is calculated which showed persistent recirculation at the downstream region of each strut intersection. The portions of the vessel where there is low and negative wall shear stress may represent locations of thrombus formation and platelet accumulation. The present results indicate that the immediate downstream regions of strut intersections are areas highly susceptible to restenosis, whereas a high shear stress at the strut intersection may cause platelet activation and free emboli formation.

Quantification of hemodynamic irregularity using oscillatory velocity index in the associations with the rupture status of cerebral aneurysms

2019 ◽  
Vol 11 (6) ◽  
pp. 614-617 ◽  
Author(s):  
Satoru Tanioka ◽  
Fujimaro Ishida ◽  
Tomoyuki Kishimoto ◽  
Masanori Tsuji ◽  
Katsuhiro Tanaka ◽  
...  
Keyword(s):  
Shear Stress ◽  
Wall Shear Stress ◽  
Cerebral Aneurysms ◽  
Flow Patterns ◽  
Hemodynamic Parameter ◽  
Hemodynamic Parameters ◽  
Unstable Flow ◽  
Ruptured Aneurysms ◽  
Oscillatory Velocity ◽  
Wall Shear

BackgroundComplex and unstable flow patterns are reported to be associated with the rupture status of cerebral aneurysms, while their evaluation depends on qualitative analysis of streamlines of bloodflow. Oscillatory velocity index (OVI) is a hemodynamic parameter to quantify flow patterns. The aim of this study is to elucidate the associations between OVI and the rupture status of cerebral aneurysms.MethodsOne hundred and twenty-nine ruptured and unruptured cerebral aneurysms were analyzed with computational fluid dynamics under pulsatile flow conditions. With the use of median value of OVI, all aneurysms were divided into high and low OVI groups. Statistical analysis was performed to compare rupture status, and morphological and hemodynamic parameters between the two groups.ResultsThe median value of OVI was 0.006. High OVI was more likely observed in ruptured aneurysms (P=0.028) and associated with irregular shape, complex flow patterns, and unstable flow patterns (P<0.001, respectively). In morphological parameters, maximum size, aspect, projection, size, and volume-to-ostium area ratios were significantly higher in the high OVI group (P<0.001, respectively). In hemodynamic parameters, wall shear stress and wall shear stress gradient were significantly lower, and oscillatory shear index and gradient oscillatory number were significantly higher in the high OVI group (P<0.001, respectively).ConclusionHigh OVI was associated with rupture status, and morphological and hemodynamic characteristics of ruptured aneurysms. These results indicate that OVI may serve as a valuable hemodynamic parameter for diagnosing rupture status and risks of aneurysms.

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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