Longitudinal Effect of Wall Shear Stress on the Amount of Intimal- Medial Thickening of Venous Wall in Arteriovenous Fistula

1 ABSTRACT Arteriovenous fistula (AVF) maturation failure is mainly due to venous stenosis characterized by significant amount of intima-media thickening (IMT). Although hemodynamic endpoints are believed to play a crucial role in pathogenesis of venous stenosis, the exact mechanism behind this is unclear. Our hypothesis is that longitudinal (temporal) changes of hemodynamic parameters, specifically wall shear stress (WSS), influences amount of IMT in maturation process of AVF. AVFs were created in curved (C-AVF) and straight (S-AVF) configurations between femoral artery and vein of 3 pigs. CT-scans and ultrasound were utilized to calculate WSS at 2D (D: days), 7D, and 28D post-surgery. IMT was measured at 4 histological blocks along the vein of AVFs. It was found that C-AVF underwent outward remodeling characterized by consistent increase in venous diameter and larger IMT. This remodeling process was governed by negative temporal gradient of WSS (τ·) [-0.99 ± 0.60 dyn/cm/day]. In contrast, S-AVF underwent inward remodeling characterized by temporal decrease in venous diameter and relatively smaller IMT. This remodeling process was governed by positive τ· (0.42 ± 0.6 dyn/cm/day). In summary, temporal gradient of WSS influences IMT. Temporal decrease of WSS in C-AVF resulted in vasodilation and outward growth of wall (favorable to maturation). However, temporal increase in WSS in S-AVF leaded to vasoconstriction and inward growth of wall (detrimental to maturation). Thus, clinically it can be of great importance to surgeons to create AVF in a configuration that can result in favorable hemodynamic parameters and histological end-points.