Abstract
Arteriovenous graft (AVG) is artificially made with graft for hemodialysis in the patients with renal failure. Stenosis in the arterial or venous anastomosis of AVG results in its malfunction. Here, we made an AVG hemodynamic model with three different anastomotic angles (20°, 30°, 40°) and analyzed hemodynamic parameters such as velocity vectors, WSS and OSI in the arterial and venous anastomosis to find what helps in developing new surgical techniques to reduce stenosis in the anastomosis. Recirculation flow, low WSS and high OSI in the venous anastomosis were demonstrated in 30° and 40° models, and recirculation flow, high WSS and high OSI in the arterial anastomosis were shown in all models. Conclusively, higher anastomosis angle in the venous anastomosis cause stenosis, but stenosis in the arterial anastomosis happens irregardless of anastomosis angle.
1. Introduction
The incidence of renal failure is increasing due to increase in aged people and patients with diabetes mellitus. The treatments of renal failure are kidney transplantation or dialysis. The limitation of kidney donors drives most patients with renal failure to dialysis, peritoneal dialysis or hemodialysis. Peritoneal dialysis takes a longer time and more frequent laps to do than hemodialysis. For the reasons, hemodialysis is commonly used.
Arteriovenous fistula (AVF) should be made artificially for hemodialysis. Arteriovenous graft (AVG) is a kind of arteriovenous fistulas, and it connects the artery and vein with graft to supply a large vessel for needling of hemodialysis. The luminal patency of AVG like Figure 1 is mainly upon the patency at the arterial or venous anastomosis. Stenosis in the venous anastomosis is more common and results in AVG dysfunction [1-3]. New surgical techniques at the anastomosis are required to reduce stenosis and hemodynamic models are needed to experiment new techniques.
In the present study, hemodynamics in AVG was numerically investigated with computational fluid dynamics. In the simulation, the three-dimensional geometry of the artery, vein and graft is used for computational mesh, and transient velocity profile of blood flow measured in ultrasonography is used for inlet and outlet boundary condition. Using this system, various simulations are carried out to analyze the effects of geometry of the artery, vein and graft on flow patterns and WSS and OSI distributions [4-6].
2. Numerical Analysis
2.1. Geometry Modeling and Mesh Generation
Figure 2 shows that 3D modeling was performed by Design modeler. Anastomosis angle (θ) is set to 20˚, 30˚, 40˚. To calculate the flow in geometry, computational mesh was generated with ICEM CFD using FEM (Finite Element Method) as shown in Figure 2. The total number of elements and nodes is 351,584 and 323,907 respectively.