Is the Maturation of Arteriovenous Fistulas a Mechanical or Biological Problem?

2016 ◽  
Author(s):  
Daniel Jodko ◽  
Damian Obidowski ◽  
Piotr Reorowicz ◽  
Krzysztof Jozwik
Keyword(s):  
High Pressure ◽  
Blood Flow ◽  
Shear Stress ◽  
Flow Rate ◽  
Blood Flow Rate ◽  
Average Diameter ◽  
Patient Specific ◽  
Maturation Process ◽  
Arteriovenous Fistulas ◽  
Biological Problem

During the maturation the high pressure blood from the artery inflows directly to the vein, extends its diameter, and finally the blood flow rate in the vein is even 500-times greater than normal one. The changes of the wall shear stress (WSS) in the vein are thought to play a key role in the remodelling of its wall. However, this process is still not well understood. The aim of this paper is to show an innovative approach for modelling of the vein deformation during the maturation process of a-v fistulas. Dilation of the vein was modelled as two-step complex biomechanical process. The obtained results concerning final diameter of the vein are compared with average diameter obtained for large group of patients. Moreover, this study shows the changes in the flow rate and the WSS that occur after maturation in the patient-specific fistula.

Sensitivity of patient-specific numerical simulation of cerebal aneurysm hemodynamics to inflow boundary conditions

2007 ◽  
Vol 106 (6) ◽  
pp. 1051-1060 ◽  
Author(s):  
Prem Venugopal ◽  
Daniel Valentino ◽  
Holger Schmitt ◽  
J. Pablo Villablanca ◽  
Fernando Viñuela ◽  
...  
Keyword(s):  
Blood Flow ◽  
Shear Stress ◽  
Boundary Conditions ◽  
Numerical Simulations ◽  
Flow Rate ◽  
Artery Aneurysm ◽  
Blood Flow Rate ◽  
Patient Specific ◽  
Stress Distributions ◽  
Flow Rates

Object Due to the difficulty of obtaining patient-specific velocity measurements during imaging, many assumptions have to be made while imposing inflow boundary conditions in numerical simulations conducted using patient-specific, imaging-based cerebral aneurysm models. These assumptions can introduce errors, resulting in lack of agreement between the computed flow fields and the true blood flow in the patient. The purpose of this study is to evaluate the effect of the assumptions made while imposing inflow boundary conditions on aneurysmal hemodynamics. Methods A patient-based anterior communicating artery aneurysm model was selected for this study. The effects of various inflow parameters on numerical simulations conducted using this model were then investigated by varying these parameters over ranges reported in the literature. Specifically, we investigated the effects of heart and blood flow rates as well as the distribution of flow rates in the A1 segments of the anterior cerebral artery. The simulations revealed that the shear stress distributions on the aneurysm surface were largely unaffected by changes in heart rate except at locations where the shear stress magnitudes were small. On the other hand, the shear stress distributions were found to be sensitive to the ratio of the flow rates in the feeding arteries as well as to variations in the blood flow rate. Conclusions Measurement of the blood flow rate as well as the distribution of the flow rates in the patient's feeding arteries may be needed for numerical simulations to accurately reproduce the intraaneurysmal hemodynamics in a specific aneurysm in the clinical setting.

scholarly journals Patient-specific computational haemodynamics associated with surgical creation of an arteriovenous fistula

2021 ◽  
Author(s):  
George Hyde-Linaker ◽  
Pauline Hall Barrientos ◽  
Sokratis Stoumpos ◽  
Asimina Kazakidi
Keyword(s):  
Blood Flow ◽  
Flow Rate ◽  
Disease Patient ◽  
Blood Flow Rate ◽  
Fold Increase ◽  
Transitional Flow ◽  
Patient Specific ◽  
Venous Anastomosis ◽  
End Stage

Abstract Despite arteriovenous fistulae (AVF) being the preferred vascular access for haemodialysis, high primary failure rates (30-70%) and low one-year patency rates (40-70%) hamper their use. The haemodynamics within the vessels of the fistula change significantly following surgical creation of the anastomosis and can be a surrogate of AVF success or failure. Computational fluid dynamics (CFD) can crucially predict AVF outcomes through robust analysis of a fistula’s haemodynamic patterns, which is impractical in-vivo. We present a proof-of-concept CFD framework for characterising the AVF blood flow prior and following surgical creation of a successful left radiocephalic AVF in a 20-year-old end-stage kidney disease patient. The reconstructed vasculature was generated utilising multiple contrast-enhanced magnetic resonance imaging (MRI) datasets. Large eddy simulations were conducted for establishing the extent of arterial and venous remodelling. Following anastomosis creation, a significant 2-3-fold increase in blood flow rate was induced downstream of the left subclavian artery. This was validated through comparison with post-AVF patient-specific phase-contrast data. The increased flow rate yielded an increase in time-averaged wall shear stress (TAWSS), a key marker of adaptive vascular remodelling. We have demonstrated TAWSS and oscillatory shear distributions of the transitional-flow in the venous anastomosis are predictive of AVF remodelling.

Effects of Age and Diabetes on Blood Flow Rate and Primary Outcome of Newly Created Hemodialysis Arteriovenous Fistulas

1998 ◽  
Vol 18 (2) ◽  
pp. 96-100 ◽  
Author(s):  
Shuei-Liong Lin ◽  
Ching-Huai Huang ◽  
Huan-Sheng Chen ◽  
Wei-An Hsu ◽  
Chung-Jen Yen ◽  
...  
Keyword(s):  
Blood Flow ◽  
Flow Rate ◽  
Primary Outcome ◽  
Blood Flow Rate ◽  
Arteriovenous Fistulas

Numerical Investigation for the Effect of Blood Flow Rate and Asymmetric Bifurcation Angle on the Anterior Circulation Aneurysm Formation

2011 ◽  
Author(s):  
Soyoon Kim ◽  
Kyoungchul Ro ◽  
Hong Sun Ryou
Keyword(s):  
High Pressure ◽  
Blood Flow ◽  
Blood Vessel ◽  
Flow Rate ◽  
Rate Ratio ◽  
Arterial Wall ◽  
Blood Flow Rate ◽  
Flow Rate Ratio ◽  
Anterior Circulation ◽  
Bifurcation Angle

Most of aneurysms in the cranial cavity occur at the bifurcation of anterior circulation system. A cerebral aneurysm is easily ruptured, and it is fatal for most patients. Generally it is known that aneurysm occurs when arterial wall is deformed by high pressure or high wall shear stress (WSS). A blood flow pattern and the geometry and the blood vessel are important factors for aneurysm formation and the location. The transient interaction between blood flow and the arterial wall affects for simulating deformation of the blood vessel. Thus, numerical analysis is performed for various bifurcation angles and flow rate ratio in bifurcation artery with different diameters to predict the location of aneurysm by hemodynamic characteristics of blood flow. A bifurcation angle between the internal carotid artery and the anterior cerebral artery (ACA) increased, a region of high pressure moved to the bifurcated artery with larger bifurcation angle when ratio of blood flow rate is constant case. When the ratio of blood flow increased, the region of high wall shear stress moved to the side of large flow rate ratio. Our results showed that the high WSS or high pressure region occur at the location of aneurysm as mentioned in the clinical research. Thus, this indicates that the geometry of blood vessel and blood flow rate affect the location of the anterior circulation aneurysm.

scholarly journals Integrating Patient-Specific Electrocardiogram Signals and Image-Based Computational Fluid Dynamics Method to Analyze Coronary Blood Flow in Patients during Cardiac Arrhythmias

2019 ◽  
Vol 40 (2) ◽  
pp. 264-272
Author(s):  
Szu-Hsien Chou ◽  
Kuan-Yu Lin ◽  
Zhen-Ye Chen ◽  
Chun-Jung Juan ◽  
Chien-Yi Ho ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Blood Flow ◽  
Coronary Artery ◽  
Cardiac Arrhythmia ◽  
Coronary Arteries ◽  
Flow Rate ◽  
Blood Flow Rate ◽  
Patient Specific ◽  
Ecg Signals

Abstract Purpose The aim of this study was to use the computational fluid dynamics (CFD) method, patient-specific electrocardiogram (ECG) signals, and computed tomography three-dimensional image reconstruction technique to investigate the blood flow in coronary arteries during cardiac arrhythmia. Methods Two patients with premature ventricular contraction-type cardiac arrhythmia and one with atrial fibrillation-type cardiac arrhythmia were investigated. The inlet velocity of the coronary artery in simulation was applied with the measured velocity profile of the left ventricular outflow tract (LVOT) from the Doppler echocardiography. The measured patient central aortic blood pressure waveform was employed for the coronary artery outlet in simulation. The no-slip boundary condition was applied to the arterial wall. Results For the patient with irregular cardiac rhythms (Case I), the coronary blood flow rate under the shortened and lengthened cardiac rhythms were 0.66 and 0.96 mL/s, respectively. In Case II, the maximum velocity at the LVOT under a normal heartbeat was found to be 101 cm/s, whereas the average value was 73 cm/s. In Case III, the patient was also diagnosed with a congenital stenosis problem at the myocardial bridge (MCB) at the LAD. The measured blood flow rate at the MCB of the LAD for the three heartbeats in Case III was found to be 0.68, 1.08, and 1.14 mL/s. Conclusion The integration of patient-specific ECG signals and image-based CFD methods can clearly analyze hemodynamic information for patients during cardiac arrhythmia. The cardiac arrhythmia can reduce the blood flow in the coronary arteries.

Comparative Study of Hemodialysis in Arteriovenous Fistulas in Low Versus High Blood Flow Rate

2021 ◽  
Vol 24 (1) ◽  
pp. 66-71
Author(s):  
Sultan Abdulwadou ◽  
Ali Twyla Almutairi ◽  
Fahad H. Alhazmi ◽  
Abdulaziz A. Qurashi ◽  
Abdulrahman Saleh Alha ◽  
...  
Keyword(s):  
Blood Flow ◽  
Comparative Study ◽  
Flow Rate ◽  
Blood Flow Rate ◽  
Arteriovenous Fistulas

scholarly journals Blood flow rate and wall shear stress in seven major cephalic arteries of humans

2019 ◽  
Vol 236 (3) ◽  
pp. 522-530
Author(s):  
Roger S. Seymour ◽  
Qiaohui Hu ◽  
Edward P. Snelling
Keyword(s):  
Blood Flow ◽  
Shear Stress ◽  
Wall Shear Stress ◽  
Flow Rate ◽  
Blood Flow Rate ◽  
Wall Shear

scholarly journals Modeling autoregulation in three-dimensional simulations of retinal hemodynamics

2016 ◽  
Vol 1 (1) ◽  
pp. 88-115
Author(s):  
Matteo Aletti ◽  
Jean-Frédéric Gerbeau ◽  
Damiano Lombardi
Keyword(s):  
Experimental Data ◽  
Blood Flow ◽  
Flow Rate ◽  
Stokes Equations ◽  
Three Dimensional ◽  
Blood Flow Rate ◽  
Patient Specific ◽  
Initial Attempt ◽  
Structural Part ◽  
3D Network

Purpose: Autoregulation is a mechanism necessary to maintain an approximately constant blood flow rate in the microcirculation when acute changes in systemic pressure occur. Failure of autoregulation in the retina has been associated with various diseases, including glaucoma. In this work, we propose an initial attempt to model autoregulation in a 3D network of retinal arteries.Methods: The blood flow is modeled with the time-dependent Stokes equations. The arterial wall model includes the endothelium and the smooth muscle fibers. Various simplifying assumptions lead to a fluid-structure model where the structural part appears as a boundary condition for the fluid. The numerical simulations are performed on a patient-specific network of 25 segments of retinal arteries located in the inferior temporal quadrant.Results: The simulations performed on the patient-specific artertial network have provided velocities which are in good agreement with published experimental data. In addition, the model allowed to reproduce flow rate-pressure curves which are comparable with experimental data or results obtained with 0D models. In particular, a characteristic plateau of the flow rate has been found for pressures ranging from 40 to 60 mmHg.Conclusion: This work proposes the first 3D simulation of blood flow in a real network of retinal arteries and it also incorporates an autoregulation mechanism. This can be viewed as a first step towards a more complete 3D model of the hemodynamic of the eye.

The Effect of Furosemide on the Intrarenal Blood Flow Distribution in the Dog

1972 ◽  
Vol 50 (8) ◽  
pp. 774-783 ◽  
Author(s):  
Serge Carrière ◽  
Michel Desrosiers ◽  
Jacques Friborg ◽  
Michèle Gagnan Brunette
Keyword(s):  
Blood Flow ◽  
Flow Rate ◽  
Urine Volume ◽  
Flow Distribution ◽  
Blood Flow Rate ◽  
Initial Distribution ◽  
Blood Flow Distribution ◽  
Intrarenal Blood Flow ◽  
Femoral Blood ◽  
Furosemide Administration

Furosemide (40 μg/min) was perfused directly into the renal artery of dogs in whom the femoral blood pressure was reduced (80 mm Hg) by aortic clamping above the renal arteries. This maneuver, which does not influence the intrarenal blood flow distribution, produced significant decreases of the urine volume, natriuresis, Ccreat, and CPAH, and prevented the marked diuresis normally produced by furosemide. Therefore the chances that systemic physiological changes occurred, secondary to large fluid movements, were minimized. In those conditions, however, furosemide produced a significant increase of the urine output and sodium excretion in the experimental kidney whereas Ccreat and CPAH were not affected. The outer cortical blood flow rate (ml/100 g-min) was modified neither by aortic constriction (562 ± 68 versus 569 ± 83) nor by the subsequent administration of furosemide (424 ± 70). The blood flow rate of the outer medulla in these three conditions remained unchanged (147 ± 52 versus 171 ± 44 versus 159 ± 54). The initial distribution of the radioactivity in each compartment remained comparable in the three conditions. In parallel with the results from the krypton-85 disappearance curves, the autoradiograms, silicone rubber casts, and EPAH did not suggest any change in the renal blood flow distribution secondary to furosemide administration.

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