Fractional Flow Reserve and Instantaneous Wave-Free Ratio Predict Pathological Wall Shear Stress in Coronary Arteries: Implications for Understanding the Pathophysiological Impact of Functionally Significant Coronary Stenoses.

Background The pathophysiological mechanism behind adverse outcomes associated with ischemia-inducing epicardial coronary stenoses and microcirculatory dysfunction remains unclear. Wall shear stress (WSS) plays an important role in atherosclerotic plaque progression and vulnerability. We aimed to evaluate the relationship between WSS, functionally significant epicardial coronary stenoses, and microcirculatory dysfunction. Methods and Results Patients undergoing invasive coronary physiology testing were included. Fractional flow reserve, instantaneous wave-free ratio, and the index of microcirculatory resistance were measured. Quantitative coronary angiography was used to obtain the lesion percentage diameter stenosis. Computational fluid dynamics analysis was performed to calculate WSS parameters. Multiple regression analysis was performed to calculate the standardized regression coefficient (ß) for the coronary physiology indices. A total of 107 vessels from 88 patients were included. Fractional flow reserve independently predicted the total area of low WSS (ß=-0.44; 95% CI, -0.62 to -0.25; P<0.001) and maximum lesion WSS (ß=-0.53; 95% CI, -0.70 to -0.36; P<0.001) after adjusting for percentage diameter stenosis and index of microcirculatory resistance. Similarly, instantaneous wave-free ratio also independently predicted the total area of low WSS (ß=-0.45; 95% CI, -0.62 to -0.28; P<0.001) and maximum lesion WSS (ß=-0.58; 95% CI, -0.73 to -0.43; P<0.001). The index of microcirculatory resistance did not predict either low or high WSS. Conclusions Fractional flow reserve and instantaneous wave-free ratio independently predicted the total burden of low WSS and maximum lesion WSS in coronary arteries. No relationship was found between microcirculatory dysfunction and WSS.

Effects of different non-Newtonian models on unsteady blood flow hemodynamics in patient-specific arterial models with in-vivo validation.

The aim of this study is to demonstrate the implications of using different blood rheological models in the simulation of blood flow dynamics in atherosclerotic coronary arteries. Computational fluid dynamics simulation was performed using three-dimensional (3D) patient-specific models of diseased left anterior descending (LAD) coronary arteries with varying degrees of stenosis severity. The three-dimensional arterial models were reconstructed from 3D quantitative coronary angiography, and input flow conditions were prescribed with blood flow conditions measured in-vivo. Different blood viscosity models were used for the simulations, and they include Newtonian and also non-Newtonian models such as Bingham, Carreau, Carreau-Yasuda, Casson, modified Casson, Cross, modified Cross, simplified Cross, Herschel Bulkley, Kuang-Luo (K-L), PowellErying, modified PowellErying, Power-law, Quemada and Walburn-Schneck models. Results from this study show that the time-averaged velocity at the centre of the arteries produced in the CFD simulations that uses the Carreau, modified Casson or Quemada blood viscosity models corresponded exceptionally well with the clinical measurements regardless of stenosis severities and hence, highlights the usefulness of these models to determine the potential determinants of blood vessel wall integrity such as dynamic blood viscosity, blood velocity and wall shear stress.

Computational investigation of stenosis in curvature of coronary artery within both dynamic and static models.

BACKGROUND AND OBJECTIVE: Blood flow variation during cardiac cycle is the main mechanism of atherosclerotic development which is dependent on. METHODS: The present work mainly tends to investigate stenosis effect in dynamic curvature of coronary artery. This paper presents numerical investigations on wall shear stress profiles in three-dimensional pulsatile flow through curved stenotic coronary arteries for both static and dynamic model. In order to do so, three-dimensional models related to the curved arteries with two degrees of stenosis (30% and 50%). RESULTS: Lower amount of wall shear stress is found near the inner wall of artery distal to the plaque region (stenosis) and in both percentages of stenosis the maximum wall shear stress will accrue in the middle of the stenosis; however it is much more in the higher rate of stenosis. CONCLUSIONS: A chaotic wall shear stress region is also observed downstream of stenosis in the severe stenosis case. Finally it concluded that the arterial wall motion affects the wall shear stress and the plaque formation site.

Associations between local haemodynamics and carotid intraplaque haemorrhage with different stenosis severities: A preliminary study based on MRI and CFD.

The relationship between carotid blood flow and carotid intraplaque haemorrhage (IPH) is not fully understood. This study was to investigate the relationship between local haemodynamics and carotid plaques with IPH associated with severe artery stenosis. Fifty-nine patients with carotid atherosclerosis were enrolled in this study and underwent magnetic resonance imaging (MRI) measurement. IPH and non-IPH compositions were differentiated based on plaque sequences. Haemodynamic simulations were performed by using computational fluid dynamics (CFD). All the carotids were categorised into IPH and non-IPH groups. In each group, the artery stenosis was divided into mild (<50%), moderate (50-70%) and severe (>70%) subgroups. Maximum wall shear stress (mWSS) was calculated and comparisons made between IPH and non-IPH groups using independent t-test. Furthermore, the relationship between mWSS and IPH volume was examined using Pearson's correlation. The mWSS result calculated from the IPH group was significantly higher than that of the non-IPH group; at mild stenosis (P = 0.001) and moderate stenosis (P = 0.002) respectively. However, there was no significant difference in cases of severe stenosis (P = 0.42). Furthermore, the results showed a positive correlation between mWSS and IPH volume (r = 0.763, P < 0.001) in the cases of stenosis of less than 70%. mWSS was found to be significantly associated with IPH for carotids with stenosis of less than 70%. This highlights that mWSS is a potential quantitative parameter for the risk diagnosis of the carotid atherosclerosis.

Haemodynamic impacts of myocardial bridge length: A congenital heart disease.

OBJECTIVES: There is an association between long and thick myocardial bridging (MB), haemodynamic perturbations and increased risk of myocardial infarction. This study aims to investigate the alteration in coronary haemodynamics with increasing the length of MB. METHODS: Angiography and intravascular ultrasound were performed in 10 patients with varying length of MB in the left anterior descending (LAD) artery. In silico models of MB were developed based on the reconstructed three-dimensional model of the LAD. The entire LAD was divided into 3 segments, proximal (pre-bridge), bridge and distal (post-bridge). Transient computational fluid dynamics simulations were performed to derive distribution of blood residence time and wall shear stress (WSS) over entire vessel including proximal, bridge and distal segments. RESULTS: With increasing the length of MB, a decreasing trend was observed in the WSS over proximal segment whereas an increasing trend was found in the WSS over bridge segment. When patients were divided into 2 groups based on the average length of MB in the whole cohort (Lave = 23.92 mm), patients with bridges longer than Lave had smaller WSS and higher residence time in the proximal segment compared to those with bridges shorter than Lave (0.59 ± 0.31 vs 0.21 ± 0.14 Pa and 0.0021 ± 0.0015 vs 0.0045 ± 0.0021 s). In contrast, patients with bridges longer than Lave had greater WSS in the bridge segment compared to those with bridges shorter than Lave (1.37 ± 1.66 vs 2.53 ± 3.14 Pa). No significant difference was found in the distal WSS of patients with short and long bridges. CONCLUSION: Our findings revealed a direct relationship between the length of MB and haemodynamic perturbations in the proximal segment such that the increased length of MB is associated with decreased WSS and increased residence time.

Hydrogenation-controlled mechanical properties in graphene helicoids: exceptional distribution-dependent behavior.

The ever-increasing development of nanotechnology has led to the creation of nanomaterials with spiral geometry such as graphene helicoids (GHs) that are mainly used for mechanical, chemical, and electrical applications. Controlling the properties of these nanomaterials with geometric changes and functionalizations is the most common and accessible task. However, functionalization leads to specific applications. In the present research, using molecular dynamics simulation, mechanical properties of pristine and functionalized GHs have been investigated for various geometries and H-coverages. Also, hydrogenation has been performed for patterned and random distributions. The random H-coverage up to 10 percent results in a decrease in the Young's modulus. Also, by increasing the percentage of H-coverage beyond 10 percent, no conspicuous alteration is observed in the Young's modulus, while the ultimate strain is reduced. By examining the effect of temperature rise on the properties of pristine and functionalized GHs, a sharp decrease in the strain range is observed for both. In addition, it has been shown that the toughness is severely reduced by decreasing the external and internal radii of pristine and functionalized GHs. Investigating the mechanical properties of pristine and hydrogenated GHs leads to better control of the mechanical properties of these nanoparticles and optimal efficiency in nano-scale devices.

Corrigendum to "Haemodynamic impacts of myocardial bridge length: A congenital heart disease" [Comput. Methods Progr. Biomed., 175 (2019) 25-33].

In this corrigendum, the authors would like to acknowledge the cardiac catheterization laboratory staff at Tehran Heart Center for their assistance in performing the studies under the ethics application TH38-02-2017-20.

Development of an innovative technology to segment luminal borders of intravascular ultrasound image sequences in a fully automated manner.

Although intravascular ultrasound (IVUS) is the commonest intravascular imaging modality, it still is inefficient for clinical use as it requires laborious manual analysis. This study demonstrates the feasibility of a near real-time fully automated technology for accurate identification, detection, and quantification of luminal borders in intravascular images. This technology uses a combination of the novel approaches of a self-tuning engine, dynamic and static masking systems, radar-wise scan, and contour correction cycle method. The performance of the computer algorithm developed based on this technology was tested on a sequence of IVUS and True Vessel Characterization (TVC) images obtained from the left anterior descending (LAD) artery of 6 patients with coronary artery disease. The accuracy of the algorithm was evaluated by comparing luminal borders traced manually with those detected automatically. The processing time of the developed algorithm was also tested on a Dell laptop with an Intel Core i7-8750H Processor (4.1 GHz with 6 cores, 9 MB Cache). Linear regression and Bland-Altman analyses indicated high correlation between manual and automatic tracings (Y = 0.80 × X+1.70, R2 = 0.88 & 0.67 ±â€¯1.31 (bias±SD)). Whereas analysis of 2000 IVUS images using one CPU core with a 30% load took 23.12 min, the same analysis using six CPU cores with 90% load took 1.0 min. The performance, accuracy, and speed of the presented state-of-the-art technology demonstrates its capacity for use in clinical settings.

Relationship between myocardial bridge compression severity and haemodynamic perturbations.

OBJECTIVES: This study aims to examine the alteration in coronary haemodynamics with increasing the severity of vessel compression caused by myocardial bridging (MB). METHODS: Angiography and intravascular ultrasound were performed in 10 patients with MB with varying severities of systolic compression in the left anterior descending (LAD) artery. Computer models of MB were developed and transient computational fluid dynamics simulations were performed to derive distribution of blood residence time and shear stress. RESULTS: With increasing the severity of bridge compression, a decreasing trend was observed in the shear stress over proximal segment whereas an increasing trend was found in the shear stress over bridge segment. When patients were divided into 2 groups based on the average systolic vessel compression in the whole cohort (%CRave = 27.38), patients with bridges with major systolic compression (>%CRave) had smaller shear stress and higher residence time in the proximal segment compared to those with bridges with minor systolic compression (<%CRave) (0.37 ± 0.23 vs 0.69 ± 0.29 Pa and 0.0037 ± 0.0069 vs 0.022 ± 0.0094 s). In contrast, patients with bridges with major systolic compression had greater shear stress in the bridge segment compared to those with bridges with minor systolic compression (2.49 ± 2.06 vs 1.13 ± 0.89 Pa). No significant difference was found in the distal shear stress of patients with bridges with major and minor systolic compression. CONCLUSION: Our findings revealed a direct relationship between the severity of systolic compression of MB and haemodynamic perturbations in the proximal segment such that the increased systolic vessel compression was associated with decreased shear stress and increased blood residence time.

Myocardial bridging and endothelial dysfunction - Computational fluid dynamics study.

Myocardial bridging (MB) is associated with endothelial dysfunction in patients with angina and non-obstructive coronary artery disease. This study aims to determine if there is a link between abnormal blood flow patterns and endothelial dysfunction in patients with MB. Ten patients with MB in their left anterior descending (LAD) artery were selected, 5 of whom had endothelial dysfunction and 5 had no endothelial dysfunction based on their response to acetylcholine. Similarly, 10 patients without MB in their LAD, 5 of whom had endothelial dysfunction and 5 of whom had no endothelial dysfunction, were studied as a control group. Transient computational fluid dynamics simulations were performed to derive wall shear stress (WSS) over the entire vessel including proximal, middle and distal segments. Patients with MB and endothelial dysfunction had lower WSS in the proximal LAD and greater WSS in the mid-LAD than patients with MB but without endothelial dysfunction. When comparing patients with endothelial dysfunction, those with MB had significantly lower shear stress in the proximal LAD (0.32 ±â€¯0.14 Pa (with MB) vs 0.71 ±â€¯0.38 Pa (without MB), p = 0.01) and greater shear stress in the mid-LAD (2.81 ±â€¯1.20 Pa (with MB) vs 1.66 ±â€¯0.31 Pa (without MB), p = 0.014) than patients without MB. Our findings demonstrated that the presence of MB significantly contributes to low WSS and endothelial dysfunction relationship.

The relationship between coronary lesion characteristics and pathologic shear in human coronary arteries.

BACKGROUND: Pathological shear stress is associated with distinct pathogenic biological pathways relevant to coronary thrombosis and atherogenesis. Although the individual effects of lesion characteristics including stenosis severity, eccentricity and lesion length on coronary haemodynamics is known, their relative importance remains poorly understood. METHODS: Computational fluid dynamics (CFD) was implemented for haemodynamic analysis of 104 coronary arteries. For each coronary artery, maximum shear stress at the site of maximal stenosis, average shear stress over the sites of maximal stenosis segment, average shear stress in the proximal segments and average shear stress in the distal segments were determined. In addition, the area of low wall shear stress (ALWSS) sites in post-stenotic regions were quantified as a proportion of the vessel segment. RESULTS: With increasing stenosis severity, eccentricity and lesion length, maximal and average shear stress over the sites of maximal stenosis and ALWSS increased whereas average shear stress in the proximal segments decreased. Two-way ANCOVA analysis revealed that stenosis severity and lesion length were both independent predictors of maximum shear at the site of maximal stenosis [F (1, 104) = 10.94, P = 0.001 for diameter stenosis and F (1, 104) = 6.21, P = 0.014 for lesion length] and ALWSS [F (1, 104) = 66.10, P = 0.001 for diameter stenosis and F (1, 104) = 4.23, P = 0.047 for lesion length]. CONCLUSION: Our findings demonstrate that although all lesion characteristics correlate with abnormal shear stress, only stenosis severity and lesion length are independent predictors of pathogenic physiological processes.

Remote Ischemic Preconditioning Acutely Improves Coronary Microcirculatory Function.

Background Remote ischemic preconditioning (RIPC) attenuates myocardial damage during elective and primary percutaneous coronary intervention. Recent studies suggest that coronary microcirculatory function is an important determinant of clinical outcome. The aim of this study was to assess the effect of RIPC on markers of microcirculatory function. Methods and Results Patients referred for cardiac catheterization and fractional flow reserve measurement were randomized to RIPC or sham. Operators and patients were blinded to treatment allocation. Comprehensive physiological assessments were performed before and after RIPC/sham including the index of microcirculatory resistance and coronary flow reserve after intracoronary glyceryl trinitrate and during the infusion of intravenous adenosine. Thirty patients were included (87% male; mean age: 63.1±10.0 years). RIPC and sham groups were similar with respect to baseline characteristics. RIPC decreased the calculated index of microcirculatory resistance (median, before RIPC: 22.6 [interquartile range [IQR]: 17.9-25.6]; after RIPC: 17.5 [IQR: 14.5-21.3]; P=0.007) and increased coronary flow reserve (2.6±0.9 versus 3.8±1.7, P=0.001). These RIPC-mediated changes were associated with a reduction in hyperemic transit time (median: 0.33 [IQR: 0.26-0.40] versus 0.25 [IQR: 0.20-0.30]; P=0.010). RIPC resulted in a significant decrease in the calculated index of microcirculatory resistance compared with sham (relative change with treatment [mean±SD] was -18.1±24.8% versus +6.1±37.5; P=0.047) and a significant increase in coronary flow reserve (+41.2% [IQR: 20.0-61.7] versus -7.8% [IQR: -19.1 to 10.3]; P<0.001). Conclusions The index of microcirculatory resistance and coronary flow reserve are acutely improved by remote ischemic preconditioning. This raises the possibility that RIPC confers cardioprotection during percutaneous coronary intervention as a result of an improvement in coronary microcirculatory function. Clinical Trial Registration URL: www.anzctr.org.au/ . Unique identifier: CTRN12616000486426.

Magnetohydrodynamic blood flow in patients with coronary artery disease.

OBJECTIVES: We aim to investigate the effect of a magnetic field with varying intensities on haemodynamic perturbations in a cohort of patients with coronary artery disease. METHODS: Transient computational fluid dynamics (CFD) simulations were performed in three-dimensional (3D) models of coronary arteries reconstructed from 3D quantitative coronary angiography. The effect of magnetic field on wall shear stress (WSS) derived parameters including maximum wall shear stress (MWSS) and size of regions with low wall shear stress (ALWSS) as well as length of flow recirculation zones were determined. RESULTS: The results showed a substantial reduction in MWSS, ALWSS and length of flow recirculation zones in the presence of magnetic field, in particular for coronaries with moderate to severe stenoses. When the whole cohort examined, time-averaged wall shear stress (TAWSS), ALWSS and the length of flow recirculation zones in the absence of magnetic field were approximately 1.71, 4.69 and 8.46 times greater than those in the presence of magnetic field, respectively. CONCLUSION: Our findings imply that an externally applied magnetic field can improve haemodynamic perturbations in human coronary arteries.

Hemodynamic analysis of carotid artery after endarterectomy: a preliminary and quantitative imaging study based on computational fluid dynamics and magnetic resonance angiography.

BACKGROUND: The carotid blood flow following carotid endarterectomy (CEA) is not fully understood. Computational fluid dynamics (CFD) is a promising method to study blood flow. This study is to investigate local hemodynamic characteristics after CEA via the use of unenhanced magnetic resonance angiography (MRA) and CFD. METHODS: Eight carotid arteries with atherosclerosis and sixteen normal carotid arteries were included in this study. Time-of-flight (TOF) and phase contrast (PC) MRA were applied for the measurement of three-dimensional artery geometries and velocity profile under CFD simulation. The hemodynamic parameters of the proximal internal carotid artery (ICA) including velocity, ICA/common carotid artery (CCA) velocity ratio, mean, maximum, minimum and gradient of wall shear stress (WSSmean, WSSmax, WSSmin and WSSG) were calculated before and after CEA. Morphologic characteristics of the carotid including bifurcation angle, tortuosity and planarity were also analyzed. RESULTS: Compared with pre-CEA, there was a significant reduction in post-CEA velocity, WSSmax, WSSmean, and WSSG, by 87.24%±13.38%, 86.86%±14.97%, 57.32%±56.71% and 69.74%±37.03% respectively, whereas WSSmin was almost unchanged. ICA/ CCA velocity ratios increased significantly after CEA. We also found that the post-CEA flow conditions were positively remodelled to approximate the conditions in normal arteries. The correlation between PC-MRA and CFD was excellent for the measurement of maximum velocity at the external carotid artery (r=0.846). CONCLUSIONS: Our preliminary results indicated that major flow dynamics were restored shortly following CEA, and CFD based on MRA measurements could be useful for quantitative evaluation of hemodynamic outcomes after CEA.

Development of a Computational Fluid Dynamics Model for Myocardial Bridging.

Computational fluid dynamics (CFD) modeling of myocardial bridging (MB) remains challenging due to its dynamic and phasic nature. This study aims to develop a patient-specific CFD model of MB. There were two parts to this study. The first part consisted of developing an in silico model of the left anterior descending (LAD) coronary artery of a patient with MB. In this regard, a moving-boundary CFD algorithm was developed to simulate the patient-specific muscle compression caused by MB. A second simulation was also performed with the bridge artificially removed to determine the hemodynamics in the same vessel in the absence of MB. The second part of the study consisted of hemodynamic analysis of three patients with mild and moderate and severe MB in their LAD by means of the developed in silico model in the first part. The average shear stress in the proximal and bridge segments for model with MB were significantly different from those for model without MB (proximal segment: 0.32 ± 0.14 Pa (with MB) versus 0.97 ± 0.39 Pa (without MB), P < 0.0001 - bridge segment: 2.60 ± 0.94 Pa (with MB) versus 1.50 ± 0.64 Pa (without MB), P < 0.0001). When all three patients were evaluated, increasing the degree of vessel compression shear stress in the proximal segment decreased, whereas the shear stress in the bridge segment increased. The presence of MB resulted in hemodynamic abnormalities in the proximal segment, whereas segments within the bridge exhibited hemodynamic patterns which tend to discourage atheroma development.

Effect of magnetic field on haemodynamic perturbations in atherosclerotic coronary arteries.

Haemodynamic perturbations including elevated blood viscosity, low and oscillatory shear stress are understood to be important pathogenic mediators in atherosclerosis. These haemodynamic abnormalities are influenced by the presence of a magnetic field. This study conducted computational fluid dynamics (CFD) analysis in 4 coronary artery models, derived from authentic human coronaries, with mild and moderate and severe stenosis severity. The aim was to investigate the effect of a static magnetic field of varying intensities on blood viscosity, areas of low wall shear stress (ALWSS), maximum wall shear stress (MWSS) and length and volume of flow recirculation zones. The results showed that the magnetic field results in both beneficial and detrimental changes in haemodynamics. The beneficial effects are lowered viscosity, decreased size of ALWSS and flow recirculation zones whereas the detrimental effect is increased MWSS. With increasing stenosis severity the effect of magnetic field becomes more prominent. An externally applied magnetic field can improve haemodynamics perturbations in human coronary arteries, especially in the setting of moderate-to-severe stenosis severity.

Flow visualisation study of spiral flow in the aorta-renal bifurcation.

The aim of this study was to analyse the flow dynamics in an idealised model of the aorta-renal bifurcation using flow visualisation, with a particular focus on the effect of aorta-to-renal flow ratio and flow spirality. The recirculation length was longest when there was low flow in the renal artery and smaller in the presence of spiral flow. The results also indicate that patients without spiral flow or who have low flow in the renal artery due to the presence of stenosis may be susceptible to heightened development of atherosclerotic lesions.

The relationship between coronary artery distensibility and fractional flow reserve.

Discordance between angiography-based anatomical assessment of coronary stenosis severity and fractional flow reserve (FFR) has been attributed to several factors including lesion length and irregularity, and the myocardial territory supplied by the target vessel. We sought to examine if coronary arterial distensibility is an independent contributor to this discordance. There were two parts to this study. The first consisted of "in silico" models of 26 human coronary arteries. Computational fluid dynamics-derived FFR was calculated for fully rigid, partially distensible and fully distensible models of the 26 arteries. The second part of the study consisted of 104 patients who underwent coronary angiography and FFR measurement. Distensibility at the lesion site (DistensibilityMLA) and for the reference vessel (DistensibilityRef) was determined by analysing three-dimensional angiography images during end-systole and end-diastole. Computational fluid dynamics-derived FFR was 0.67±0.19, 0.70±0.18 and 0.75±0.17 (P<0.001) in the fully rigid, partially distensible and fully distensible models respectively. FFR correlated with both DistensibilityMLA (r = 0.36, P<0.001) and DistensibilityRef (r = 0.44, P<0.001). Two-way ANCOVA analysis revealed that DistensibilityMLA (F (1, 100) = 4.17, p = 0.031) and percentage diameter stenosis (F (1, 100) = 60.30, p < 0.01) were both independent predictors of FFR. Coronary arterial distensibility is a novel, independent determinant of FFR, and an important factor contributing to the discordance between anatomical and functional assessment of stenosis severity.

Recirculation zone length in renal artery is affected by flow spirality and renal-to-aorta flow ratio.

Haemodynamic perturbations such as flow recirculation zones play a key role in progression and development of renal artery stenosis, which typically originate at the aorta-renal bifurcation. The spiral nature of aortic blood flow, division of aortic blood flow in renal artery as well as the exercise conditions have been shown to alter the haemodynamics in both positive and negative ways. This study focuses on the combinative effects of spiral component of blood flow, renal-to-aorta flow ratio and the exercise conditions on the size and distribution of recirculation zones in renal branches using computational fluid dynamics technique. Our findings show that the recirculation length was longest when the renal-to-aorta flow ratio was smallest. Spiral flow and exercise conditions were found to be effective in reducing the recirculation length in particular in small renal-to-aorta flow ratios. These results support the hypothesis that in renal arteries with small flow ratios where a stenosis is already developed an artificially induced spiral flow within the aorta may decelerate the progression of stenosis and thereby help preserve kidney function.

Analysis of Blood Flow Characteristics in a Model of a Mature Side-to-Side Arteriovenous Fistula.

The creation of an arteriovenous fistula (AVF) is a common surgical procedure in hemodialysis patients suffering from end-stage renal disease (ESRD). However, several complications may occur after surgery, including thrombosis, stenosis, and aneurysm. These complications are attributed to hemodynamics perturbations including pathophysiological wall shear stress (WSS) and flow recirculation zones. In this study, we present a computational hemodynamic analysis in a model of a mature side-to-side AVF, which is then validated by experimental measurements. Both computational and experimental results confirmed the presence of complex flow patterns within the AVF with vortices initially developing at the center of the venous region and gradually moving downstream, such that at four characteristic anastomosis lengths downstream, the flow disturbances became minimum. A complex pattern was also observed in WSS distribution with regions of low and high WSS identified in proximal vein and feeding artery, respectively. In addition, the temporal distribution of WSS varied significantly along the venous wall where a large portion of it remained above normal levels of WSS during systole while the area was largely normal during diastole. Our findings support the hypothesis that high WSS is not detrimental to immediate patency of AVF; however, other factors including low WSS and temporal and spatial gradients of WSS increase the risk of vascular access complications.