Anatomic configuration affects the flow rate and diameter of porcine arteriovenous fistulae

Although arteriovenous fistulae are currently the preferred form of vascular access, early failure is a significant problem. Since wall shear stress is thought to play an important role in the pathogenesis of early failure, and this stress varies markedly in different fistula configurations, we assessed the influence of configuration (curved or straight) on longitudinal changes of flow rate and lumen diameter in a porcine fistula model. Fistulae were created in eight pigs between the femoral artery and vein, with each animal having a curved and a straight configuration on opposite sides. Velocity measurements were obtained by ultrasound at the time of surgery and at intermediate time points up to 28 days. Quantification of both the configuration and the internal diameter of the fistulae was determined by CT scans. The overall rate of increased flow during each time interval (0 to 2 days, 2 to 7 days, and 7 to 28 days) was more pronounced with the curved fistulae. Moreover, the luminal diameter of curved fistulae had dilated more from the time of surgery to 28 days as compared to the straight fistulae. Thus, anatomical configuration of fistulae plays a major role in flow-mediated dilatation. Identifying the optimal configuration may result in increased diameter and consequently blood flow, and perhaps reduce the incidence of early failure.