Effect of the Anastomotic Angle on the Wall Shear Stress Profiles in the Arteriovenous Fistulae Available to Purchase

A significant number of arteriovenous fistulae (AVFs) fail to mature to support hemodialysis. Hemodynamic parameters, mainly wall shear stress (WSS), are believed to play a crucial role in the maturation or failure of AVFs. Our goal is to study the effects of the AVF configuration on the WSS profile. Idealized AVFs with 90°, 60°, and 30° anastomotic angles were created based on our previous experimental data from an in-vivo swine model [1]. The hemodynamic parameters were then obtained using numerical techniques under steady state condition. The average WSS values for our models were within range of the swine model average WSS (= 174.9±64.6 dyne/cm ²). For all AVFs, WSS was higher along the bend. The highest WSS occurred on the outer wall (OW) of the 30° AVF (= 613 dyne/cm ²) compared to the 60° (= 407 dyne/cm ²) and 90° AVFs (= 329 dyne/cm ²). WSS on the inner wall (IW) of the bend was negative with the smallest magnitude in the 90° AVF (= −91 dyne/cm ²) compared to the 60° (= −172 dyne/cm ²) and 30° AVFs (= −169 dyne/cm ²). In addition, the maximum difference in WSS (ΔWSS: measure of axial WSS gradient) was less for the 90° AVF (= 158 dyne/cm ²) than the 60° (= 170 dyne/cm ²) and 30° AVFs (= 414 dyne/cm ²). A similar trend was found on the OW with ΔWSS of 161, 405, and 870 dyne/cm ² for the 90°, 60°, 30° AVF, respectively. Moreover, AVFs with different angles can be categorized based on Dean number ( De) which showed an inverse correlation to WSS range. Thus, creating an AVF with a surgical configuration that results in a low De, representing a sharp bend with large radius of curvature, could result in a hemodynamic condition (high WSS and ΔWSS) that could have adverse effects on the fistula maturation.