Fig 1.
AVF creation using end-to-side anastomosis between jugular vein and carotid artery in the murine model.
The white arrow shows the direction of venous outflow.
Fig 2.
Contrast-enhanced CT images and segmented vascular structure.
(a) CT images in three orientations, coronal, sagittal, and axial, near the AVF. A volume rendering of the CT images is shown in the upper right to visualize vasculature and bone structure. The AVF and surrounding veins and arteries are annotated in yellow. (b) and (c) Segmented vasculature near the AVF at day 7 and day 21 post-surgery, respectively. Color coding represents distinct vessel segments: red indicates the carotid artery (with the proximal segment at bottom and distal segment at top), yellow highlights the AVF region (4 mm of length), and blue shows the main venous drainage with its characteristic ballooning of the vein starting 4 mm from the anastomosis.
Fig 3.
Computational model setup and flow rate boundary conditions for murine AVF analysis.
(a) Computational domain, boundary conditions, and mesh configuration. The three-dimensional computational domain represents the murine carotid artery-jugular vein arteriovenous fistula model (day 7 geometry shown). Boundary conditions include: velocity-based inlet conditions at both proximal and distal carotid artery ends derived from ultrasound Doppler measurements, no-slip conditions at all vessel walls, and zero-pressure outlet conditions at the venous exit. The computational mesh consists of tetrahedral elements with five prismatic boundary layers near vessel walls (upper inset) to capture near-wall flow gradients. The lower inset shows detailed mesh refinement at the arteriovenous junction. (b) Flow rate waveforms for boundary condition implementation. Pulsatile flow rate waveforms for the proximal artery (PA) and distal artery (DA) derived from ultrasound Doppler velocity measurements at day 7 and day 21 post-fistula creation. These waveforms serve as time-varying inlet boundary conditions for the computational fluid dynamics simulations, capturing the physiological flow patterns and their temporal evolution during fistula maturation.
Fig 4.
Grid convergence and temporal convergence analysis.
Pressure time history at the proximal inlet demonstrates: (i) grid independence between medium and fine meshes, with differences less than 1% throughout the cardiac cycle and (ii) periodic steady-state was achieved after two cycles, with the first cycle influenced by initial conditions. Data from the third cycle, computed with medium mesh resolution, was used for all subsequent analyses.
Table 1.
Diameters of the AVF models for day 7 and day 21 (unit: mm).
Fig 5.
Lumen diameter profiles along the vascular segments at day 7 (D7) and day 21 (D21).
The x-axis represents the distance from the anastomosis, with negative values indicating upstream segments (proximal artery [PA] and distal artery [DA]) and positive values indicating downstream segments (arteriovenous fistula [AVF]). The average AVF diameter is measured within the first 2 mm of the fistula. Cross-sections F1-F4, spaced 0.5 mm apart, indicate locations analyzed for hemodynamics in results.
Fig 6.
Flow patterns within the AVF at peak systole for day 7 (a) and day 21 (b) models.
Streamlines colored by velocity magnitude show the three-dimensional flow trajectories. Cross-sectional velocity distributions at representative locations demonstrate the spatial evolution of the flow field. The color scale represents velocity magnitude in mm/s. Cross-sectional dimensions are not to scale.
Fig 7.
Cross-sectional average velocity and pressure along the vessel centerline at peak systole for day 7 and day 21 models.
The plots show velocity (red) and pressure (blue) distributions relative to distance from the anastomosis. Both models exhibit characteristic features: a sharp velocity increase preceding the stenosis followed by deceleration, with large velocities occurring 1 mm downstream of the anastomosis. A corresponding abrupt pressure drop is observed immediately before the stenotic region. The pressure drop completes (99%) within 1.5 mm downstream of the anastomosis on day 21, whereas it only occurs 50% over the same distance on day 7.
Fig 8.
Cross-sectional maximum and average distributions of TAWSS along the centerline for day 7 and day 21.
The two horizontal lines represent the average values across the first 4 mm AVF. For day 7, peak TAWSS is localized within 0.5 mm downstream from the anastomosis, with an average value of 3 Pa across the 4 mm fistula region. By day 21, peak TAWSS shifts to 1.2 mm downstream from the anastomosis, with the average value increasing sixfold to 18 Pa across the 4 mm fistula region.
Fig 9.
Time-averaged wall shear stress (TAWSS) distributions of (a) day 7 and (b) day 21 models.
Each panel shows three-dimensional TAWSS colormaps along the vessel surfaces and representative cross-sectional (F1 to F4) distributions showing circumferential variation of TAWSS at key locations (anastomosis, stenosis, and AVF). TAWSS exhibits pronounced spatial heterogeneity, with peak values localized at the stenotic region. A significant temporal increase in TAWSS magnitude is observed from day 7 to day 21, particularly in regions of geometric constriction. The color scale represents TAWSS in Pa. Points A and B (indicated by arrows) show locations of maximum TAWSS values: 142 Pa and 37 Pa on day 7, and 134 Pa and 200 Pa on day 21, respectively. Cross-sectional dimensions are not to scale.
Fig 10.
Cross-sectional maximum and average distributions of OSI along the centerline for (a) day 7 and (b) day 21.
The two horizontal lines represent the average values across the first 4mm AVF. For day 7, peak OSI occurs within 1.0 mm downstream from the anastomosis, with an average value of 0.0025 across the 4 mm fistula region. By day 21, peak OSI extends from 1.0 to 2.5 mm downstream from the anastomosis, with the average value increasing substantially to 0.016 across the 4 mm fistula region.
Fig 11.
Oscillatory Shear Index (OSI) distributions of (a) day 7 and (b) day 21 models.
Each panel shows three-dimensional OSI colormaps along the vessel surfaces and representative cross-sectional distributions showing circumferential variation of OSI at key locations (anastomosis, stenosis, and AVF). High OSI regions are predominantly localized at the anastomosis and downstream of the stenosis. OSI demonstrates circumferential heterogeneity, with elevated values corresponding to regions of flow separation. An obvious temporal increase in OSI magnitude is observed from day 7 to day 21. The color scale represents dimensionless OSI values from 0 to 0.1. Points A and B (indicated by arrows) show locations of maximum OSI values: 0.22 and 0.17 on day 7, increasing to 0.48 and 0.26 on day 21, respectively. Cross-sectional dimensions are not to scale.
Fig 12.
Vortical structures visualized using the Q-criterion for (a) day 7 and (b) day 21 models.
Whereas vortical structures predominantly develop near vessel walls, a distinct vortex core (marked by circle) forms within the AVF vein lumen. Temporal comparison reveals increased vortical intensity on day 21 compared to day 7, particularly pronounced in stenotic regions. Although relatively small in magnitude, vortical structures are also observed to develop within the main vein. The color scale represents Q-criterion magnitude (), with positive values indicating regions where rotation dominates strain.
Fig 13.
Same-day correlations between TAWSS and AVF lumen diameter.
A strong nonlinear inverse relationship with diameter on both days was observed.