Computational Fluid Dynamics of a Vascular Access Case for Hemodialysis

2000 ◽  
Vol 123 (3) ◽  
pp. 284-292 ◽  
Author(s):  
Bogdan Ene-Iordache ◽  
Lidia Mosconi ◽  
Giuseppe Remuzzi ◽  
Andrea Remuzzi
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Blood Flow ◽  
Shear Stress ◽  
Wall Shear Stress ◽  
Radial Artery ◽  
Stress Gradient ◽  
Vascular Lesions ◽  
Patient Specific ◽  
Wall Shear

Vascular accesses (VA) for hemodialysis are usually created by native arteriovenous fistulas (AVF) or synthetic grafts. Maintaining patency of VA continues to be a major problem for patients with end-stage renal disease, since in these vessels thrombosis and intimal hyperplasia often occur. These lesions are frequently associated with disturbed flow that develops near bifurcations or sharp curvatures. We explored the possibility of investigating blood flow dynamics in a patient-specific model of end-to-end native AVF using computational fluid dynamics (CFD). Using digital subtraction angiographies of an AVF, we generated a three-dimensional meshwork for numerical analysis of blood flow. As input condition, a time-dependent blood waveform in the radial artery was derived from centerline velocity obtained during echo-color-Doppler ultrasound examination. The finite element solution was calculated using a fluid-dynamic software package. In the straight, afferent side of the radial artery wall shear stress ranged between 20 and 36 dynes/cm2, while on the inner surface of the bending zone it increased up to 350 dynes/cm2. On the venous side, proximal to the anastomosis, wall shear stress was oscillating between negative and positive values (from −12 dynes/cm2 to 112 dynes/cm2), while distal from the anastomosis, the wall shear stress returned within the physiologic range, ranging from 8 to 22 dynes/cm2. Areas of the vessel wall with very high shear stress gradient were identified on the bending zone of the radial artery and on the venous side, after the arteriovenous shunt. Secondary blood flows were also observed in these regions. CFD gave a detailed description of blood flow field and showed that this approach can be used for patient-specific analysis of blood vessels, to understand better the role of local hemodynamic conditions in the development of vascular lesions.

Comparison of morphological and rheological conditions between conventional and eversion carotid endarterectomy using computational fluid dynamics – a pilot study

Vascular ◽  
2014 ◽  
Vol 23 (5) ◽  
pp. 474-482 ◽  
Author(s):  
S Demirel ◽  
D Chen ◽  
Y Mei ◽  
S Partovi ◽  
H von Tengg-Kobligk ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Shear Stress ◽  
Wall Shear Stress ◽  
Carotid Endarterectomy ◽  
Patient Specific ◽  
Specific Data ◽  
Computational Fluid Dynamics Analysis ◽  
Carotid Bulb ◽  
Wall Shear

Purpose: To compare postoperative morphological and rheological conditions after eversion carotid endarterectomy versus conventional carotid endarterectomy using computational fluid dynamics. Basic methods: Hemodynamic metrics (velocity, wall shear stress, time-averaged wall shear stress and temporal gradient wall shear stress) in the carotid arteries were simulated in one patient after conventional carotid endarterectomy and one patient after eversion carotid endarterectomy by computational fluid dynamics analysis based on patient specific data. Principal findings: Systolic peak of the eversion carotid endarterectomy model showed a gradually decreased pressure along the stream path, the conventional carotid endarterectomy model revealed high pressure (about 180 Pa) at the carotid bulb. Regions of low wall shear stress in the conventional carotid endarterectomy model were much larger than that in the eversion carotid endarterectomy model and with lower time-averaged wall shear stress values (conventional carotid endarterectomy: 0.03–5.46 Pa vs. eversion carotid endarterectomy: 0.12–5.22 Pa). Conclusions: Computational fluid dynamics after conventional carotid endarterectomy and eversion carotid endarterectomy disclosed differences in hemodynamic patterns. Larger studies are necessary to assess whether these differences are consistent and might explain different rates of restenosis in both techniques.

scholarly journals ESTIMATION OF WALL SHEAR STRESS USING 4D FLOW CARDIOVASCULAR MRI AND COMPUTATIONAL FLUID DYNAMICS

2016 ◽  
Vol 17 (03) ◽  
pp. 1750046 ◽  
Author(s):  
E. SOUDAH ◽  
J. CASACUBERTA ◽  
P. J. GAMEZ-MONTERO ◽  
J. S. PÉREZ ◽  
M. RODRÍGUEZ-CANCIO ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Blood Flow ◽  
Shear Stress ◽  
Cardiovascular Magnetic Resonance ◽  
Magnetic Resonance ◽  
Wall Shear Stress ◽  
Thoracic Aorta ◽  
4D Flow ◽  
Wall Shear

In the last few years, wall shear stress (WSS) has arisen as a new diagnostic indicator in patients with arterial disease. There is a substantial evidence that the WSS plays a significant role, together with hemodynamic indicators, in initiation and progression of the vascular diseases. Estimation of WSS values, therefore, may be of clinical significance and the methods employed for its measurement are crucial for clinical community. Recently, four-dimensional (4D) flow cardiovascular magnetic resonance (CMR) has been widely used in a number of applications for visualization and quantification of blood flow, and although the sensitivity to blood flow measurement has increased, it is not yet able to provide an accurate three-dimensional (3D) WSS distribution. The aim of this work is to evaluate the aortic blood flow features and the associated WSS by the combination of 4D flow cardiovascular magnetic resonance (4D CMR) and computational fluid dynamics technique. In particular, in this work, we used the 4D CMR to obtain the spatial domain and the boundary conditions needed to estimate the WSS within the entire thoracic aorta using computational fluid dynamics. Similar WSS distributions were found for cases simulated. A sensitivity analysis was done to check the accuracy of the method. 4D CMR begins to be a reliable tool to estimate the WSS within the entire thoracic aorta using computational fluid dynamics. The combination of both techniques may provide the ideal tool to help tackle these and other problems related to wall shear estimation.

Impact of Thoracic Endografting on the Hemodynamics of the Native Aorta: Pre- and Postoperative Assessments of Wall Shear Stress and Vorticity Using Computational Fluid Dynamics

2020 ◽  
pp. 152660282095966
Author(s):  
Marco Midulla ◽  
Ramiro Moreno ◽  
Anne Negre-Salvayre ◽  
Jean-Paul Beregi ◽  
Stéphan Haulon ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Shear Stress ◽  
Wall Shear Stress ◽  
Aortic Rupture ◽  
Prognostic Significance ◽  
Patient Specific ◽  
Landing Zone ◽  
Cfd Models ◽  
Wall Shear

Purpose To quantify the hemodynamic consequences of thoracic endovascular aortic repair (TEVAR) by comparing the preoperative and postoperative wall shear stress (WSS) and vorticity profiles on computational fluid dynamics (CFD) simulations. Materials and Methods The pre- and postoperative computed tomography (CT) scans from 20 consecutive patients (median age 69 years, range 20–87) treated for different thoracic aortic pathologies (11 aneurysms, 5 false aneurysms, 3 penetrating ulcers, and 1 traumatic aortic rupture) were segmented to construct patient-specific CFD models using a meshless code. The simulations were run over the cardiac cycle, and the WSS and vorticity values measured at the proximal and distal landing zones were compared. Results The CFD runs provided 4-dimensional simulations of blood flow in all patients. WSS and vorticity profiles at the proximal landing zone (located in zones 0–3 in 15 patients) varied in 18 and 20 of the cases, respectively; WSS was increased in 11 cases and the vorticity in 9. Pre- and postoperative WSS median values were 4.19 and 4.90 Pa, respectively. Vorticity median values were 40.38 and 39.17 Hz, respectively. Conclusion TEVAR induces functional alterations in the native thoracic aorta, though the prognostic significance of these changes is still unknown. CFD appears to be a valuable tool to explore aortic hemodynamics, and its application in a larger series would help define a predictive role for these hemodynamic assessments.

scholarly journals The Hemodynamics of Aneurysms Treated with Flow-Diverting Stents Considering both Stent and Aneurysm/Artery Geometries

2020 ◽  
Vol 10 (15) ◽  
pp. 5239
Author(s):  
Paulo R. Cillo-Velasco ◽  
Rafaello D. Luciano ◽  
Michael E. Kelly ◽  
Lissa Peeling ◽  
Donald J. Bergstrom ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Blood Flow ◽  
Shear Stress ◽  
Wall Shear Stress ◽  
Hemodynamic Parameters ◽  
Stent Deployment ◽  
Flow Velocity Field ◽  
Relative Residence Time ◽  
Wall Shear

Flow diverting stents are deployed to reduce the blood flow into the aneurysm, which would thereby induce thrombosis in the aneurysm sac; the stents prevent its rupture. The present study aimed to examine and quantify the impacts of different flow stents on idealized configurations of the cerebral artery. In our study, we considered a spherical sidewall aneurysm located on curved and tortuous idealized artery vessels and three stents with different porosities (70, 80 and 90%) for deployment. Using computational fluid dynamics, the local hemodynamics in the presence and absence of the stents were simulated, respectively, under the assumption that the blood flow was unsteady and non-Newtonian. The hemodynamic parameters, such as the intra-aneurysmal flow, velocity field and wall shear stress and its related indices, were examined and compared among the 12 cases simulated. The results illustrated that with the stent deployment, the intra-aneurysmal flow and the wall shear stress and its related indices were considerably modified depending on both stent and aneurysm/artery geometries, and that the intra-aneurysmal relative residence time increased rapidly with decreasing stent porosity in all the vessel configurations. These results also inform the rationale for selecting stents for treating aneurysms of different configurations.

scholarly journals Computational fluid dynamics evaluation of flow reversal treatment of giant basilar tip aneurysm

2015 ◽  
Vol 21 (5) ◽  
pp. 586-591 ◽  
Author(s):  
Martin Sandve Alnæs ◽  
Kent-Andre Mardal ◽  
Søren Bakke ◽  
Angelika Sorteberg
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Shear Stress ◽  
Wall Shear Stress ◽  
Flow Reversal ◽  
Patient Specific ◽  
Parent Artery ◽  
Basilar Tip Aneurysm ◽  
Wall Shear ◽  
Artery Flow

Therapeutic parent artery flow reversal is a treatment option for giant, partially thrombosed basilar tip aneurysms. The effectiveness of this treatment has been variable and not yet studied by applying computational fluid dynamics. Computed tomography images and blood flow velocities acquired with transcranial Doppler ultrasonography were obtained prior to and after bilateral endovascular vertebral artery occlusion for a giant basilar tip aneurysm. Patient-specific geometries and velocity waveforms were used in computational fluid dynamics simulations in order to determine the velocity and wall shear stress changes induced by treatment. Therapeutic parent artery flow reversal lead to a dramatic increase in aneurysm inflow and wall shear stress (30 to 170 Pa) resulting in an increase in intra-aneurysmal circulation. The enlargement of the circulated area within the aneurysm led to a re-normalization of the wall shear stress and the aneurysm remained stable for more than 8 years thereafter. Therapeutic parent artery flow reversal can lead to unintended, potentially harmful changes in aneurysm inflow which can be quantified and possibly predicted by applying computational fluid dynamics.

NUMERICAL SIMULATION OF HEMODYNAMICS IN PORTAL VEIN WITH THROMBOSIS BY COMPUTATIONAL FLUID DYNAMICS

2014 ◽  
Vol 14 (06) ◽  
pp. 1440006 ◽  
Author(s):  
XINKAI WANG ◽  
GUOJIE LI ◽  
BIN CHEN ◽  
YANSONG PU ◽  
PENG NIE ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Shear Stress ◽  
Wall Shear Stress ◽  
Portal Vein ◽  
Mechanical Damage ◽  
Maximum Velocity ◽  
Vein System ◽  
Vein Thrombosis ◽  
Wall Shear

Portal vein thrombosis (PVT) is an important complication that is associated with cirrhotic portal hypertension. The etiology is as yet unclear but could be closely related to the hemodynamics of the portal vein system. This paper investigated the hemodynamics in the portal vein model, both with and without thrombosis, as well as the effect of obstructions on the hemodynamics of the portal vein system using the computational fluid dynamics (CFD) method. PVT can probably develop in the inlets of the portal vein as well as the left/right branches of the portal vein because the distribution of wall shear stress satisfies the conditions for PVT formation based upon the simulation of the hemodynamics in the normal portal vein model. According to the above results, geometric models for a portal vein with a thrombus were constructed and the influence of different degrees (26%, 39%, 53% and 64%) of obstructions was studied. In the model with the maximum obstruction (64% blocked), the maximum velocity of portal vein (PV) increased up to twice than in the model without thrombosis, and the maximum wall shear stress of PV in the model with thrombosis (64% blocked) increased up to 9.4 Pa, whereas it was only 1.9 Pa in the model without thrombosis (nearly one fifth of the maximum wall shear stress). Excessive wall shear stress may cause mechanical damage to the blood vessels and induce physiological changes.

A Numerical Multiscale Study of the Haemodynamics in an Image-Based Model of Human Carotid Artery Bifurcation

2009 ◽  
Author(s):  
Diego Gallo ◽  
Raffaele Ponzini ◽  
Filippo Consolo ◽  
Diana Massai ◽  
Luca Antiga ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Blood Flow ◽  
Shear Stress ◽  
Wall Shear Stress ◽  
Cardiovascular System ◽  
Vessel Wall ◽  
3D Model ◽  
Carotid Bifurcation ◽  
Wall Shear ◽  
Flow Division

The initiation and progression of vessel wall pathologies have been linked to disturbances of blood flow and altered wall shear stress. The development of computational techniques in fluid dynamics, together with the increasing performances of hardware and software allow to routinely solve problems on a virtual environment, helping to understand the role of biomechanics factors in the healthy and diseased cardiovascular system and to reveal the interplay of biology and local fluid dynamics nearly intractable in the past, opening to detailed investigation of parameters affecting disease progression. One of the major difficulties encountered when wishing to model accurately the cardiovascular system is that the flow dynamics of the blood in a specific vascular district is strictly related to the global systemic dynamics. The multiscale modelling approach for the description of blood flow into vessels consists in coupling a detailed model of the district of interest in the framework of a synthetic description of the surrounding areas of the vascular net [1]. In the present work, we aim at evaluating the effect of boundary conditions on wall shear stress (WSS) related vessel wall indexes and on bulk flow topology inside a carotid bifurcation. To do it, we coupled an image-based 3D model of carotid bifurcation (local computational domain), with a lumped parameters (0D) model (global domain) which allows for physiological mimicking of the haemodynamics at the boundaries of the 3D carotid bifurcation model here investigated. Two WSS based blood-vessel wall interaction descriptors, the Time Averaged WSS (TAWSS), and the Oscillating Shear Index (OSI) were considered. A specific Lagrangian-based “bulk” blood flow descriptor, the Helical Flow Index (HFI) [2], was calculated in order to get a “measure” of the helical structure in the blood flow. In a first analysis the effects of the coupled 0D models on the 3D model are evaluated. The results obtained from the multiscale simulation are compared with the results of simulations performed using the same 3D model, but imposing a flow rate at internal carotid (ICA) outlet section equal to the maximum (60%) and the minimum (50%) flow division obtained out from ICA in the multiscale model simulation (the presence of the coupled 0D model gives variable internal/external flow division ratio during the cardiac cycle), and a stress free condition on the external carotid (ECA).

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