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

Abstract

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.

New Insights into Dialysis Vascular Access: Molecular Targets in Arteriovenous Fistula and Arteriovenous Graft Failure and Their Potential to Improve Vascular Access Outcomes

“…Nonphysiologic WSS patterns have been linked to stenosis and venous neointimal hyperplasia development in AVF (34). Previous studies have demonstrated that endothelial cells exposed to pulsatile unidirectional WSS downregulate expression of proinflammatory, pro-oxidant, proapoptotic genes, while low and oscillatory WSS induces expression of proinflammatory, pro-oxidant, and proapoptotic mediators that activate smooth muscle proliferation and migration (35-37).…”

“…Magnetic resonance imaging and computed tomography have been used in both large-animal and clinical studies to evaluate neointimal hyperplasia development, lumen geometry, hemodynamics, and computational fluid dynamics (34,(64)(65)(66). These imaging technologies would be even more powerful if they could be applied in transgenic rodent models where the combination of pathobiology and computational fluid dynamics modeling could be studied in greater depth.…”

From basic anatomic configuration to maturation success

“…What would be the impact on maturation if newly native fi stulae included curvatures in the proximal region of the vein? For now the answers remain uncertain, but the findings of Krishnamoorthy et al 5 warrant future studies to demonstrate the plausibility of designing an optimal anatomic confi guration for human fi stulae that minimizes the failure rate. If this can be achieved, new recommendations and scientifi cally validated approaches that optimize fi stula geometry while ensuring a proper and timely maturation of the fi stula are foreseen ( Figure 1 ).…”

“…4 Th erefore, there is still an unmet necessity of basic studies to assess the role of hemodynamics, anatomy, and biology in arteriovenous fi stula maturation. Krishnamoorthy et al 5 (this issue) deal once again with the apparently simple but complex relationship between the basic anatomic shape of the fi stula and two important parameters of fistula maturation, blood flow and diameter. Using ultrasound and computed tomographic scan, these authors measured temporal changes in configu ration, internal diameter, and blood fl ow occurring in straight and curved fi stulae that were created in experimental pigs ( Figure 1 ).…”

“…It is important to note that the work of Krishnamoorthy et al 5 becomes relevant in the absence of studies intended to elucidate how geometric and hemodynamic factors such as anastomosis length and angle, vessel diameter, and fl ow distribution patterns determine fi stula maturation. Only a few attempts have been made to assess the impact of fi stula geometry on stenosis in hemodialysis patients.…”