Effect of Anastomotic Angle on Pressure Drop in Arteriovenous Fistulae

The amount of the blood flow rate to an arteriovenous fistula (AVF) is one of the primary factors that determine the likelihood of maturation. The increase in the flow rate is dependent on the amount of the resistive forces in the AVF which can be evaluated by pressure drop (Δ p). Our group has shown that the surgical configuration of AVF affects the hemodynamics and thus the remodeling within the AVF. Here, our aim is to study the effect of AVF configuration on the induced Δ p. Based on the data collected in our previous in-vivo porcine experiments, idealized models of AVFs with anastomosis angles of 30°, 60°, and 90° were created and numerically solved to find Δ p under steady-state conditions. The Δ p from the idealized models were within the same range as the experimental data (15.31 ± 3.78 mmHg). The highest and lowest Δ p were found to be 14.75 and 6.40 mmHg for the 30° and 90° AVFs, respectively. Moreover, an inverse relationship was found between the Dean number ( De) and Δ p. As De decreased with increasing radius of curvature (from higher anastomotic angles to the lower), the Δ p increased. These data suggest that creating the AVFs in a surgical configuration that results in larger De (lower radius of curvature such as 90° AVF) may achieve higher flow rate due to relatively lower Δ p. In contrast, creation of AVF with lower De which represents a sharp bend with high radius of curvature (30° AVF) could be detrimental to AVF maturation as it results in relatively higher Δ p.