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Abstract: FR-PO720

A Computational Fluid Dynamics (CFD) Approach to Optimize Arterio-Venous Fistula (AVF) Anastomotic Hemodynamics with an External Support Device (VasQ™)

Session Information

Category: Dialysis

  • 704 Dialysis: Vascular Access

Author

  • Hentschel, Dirk M., Brigham and Women's Hospital, Boston, Massachusetts, United States
Background

The complex AVF geometry induces hemodynamic changes in the juxta-anastomotic region (JAR). Multidirectional flow and oscillating wall shear stress (WSS) along the venous wall invoke undesirable inward vein remodeling through aggressive development of neointimal hyperplasia . A CFD model was utilized to study the effect of geometric parameters on hemodynamic profiles to inform optimal design of the VasQ™ device.

Methods

A fully developed 3D end-to-side AVF CFD model was evaluated through a range of artery and vein diameters (2.9-8mm) and flow volumes (40–1100 ml/min) assuming steady, laminar, Newtonian flow. 2D velocity streamline patterns were analyzed. Geometric parameters controllable by external scaffold were optimized for minimizing multidirectional flow along the venous wall (A1) and maximizing its distance from anastomosis (P1). Parameters included anastomotic angle (20°-60°), Proximal Vein (PV)/Distal Vein (DV) diameter ratio (conical shape) (1.2-2) and conical segment length(CSL) (15-25mm). Each parameter was analyzed by fixing all model values excluding the tested one.

Results

Improved flow patterns (small mean λ value; λ =A1/P1) were observed for anastomotic angle between 40°-50° (0.92±0.2) compared to angle between 20°-30° (2.3±1.7) and 60° (1.74±1.3). Optimal PV/DV (conical shape) was 1.5 (0.23±0.07) with higher λ values for PV/DV lower or higher than 1.5. λ values of 0.2±0.8, 0.27±0.05 and 0.35±0.06 for CSL of 25mm, 20mm and 15mm accordingly.

Conclusion

Improved unidirectional flow pattern directly correlated to uniform WSS in the JAR were observed for anastomotic angle between 40°-50°, conical vein shape with 1.5 PV/DV and CSL of 25mm in multiple configurations. These conclusions were the basis for designing VasQ™.

Tested geometrical parameters

Funding

  • Commercial Support