Copyright © 2019 Tracie Barber. All rights reserved.

ARTERIO-VENOUS FISTULAE

Chronic kidney disease (CKD) affects 10% of Australian adults and 1 in 9 Australian deaths had CKD as an underlying or associated cause. Besides kidney transplants, the next best treatment option is Haemodialysis which requires an arteriovenous fistula (AVF). AVF is a vascular structure surgically created to increase flow rate into a dialysis machine. In addition to increasing blood flow, the AVF increases the size of the vein which makes the cannulation procedure easier.

The flow field in an arterio-venous fistula is unusually high flow, three-dimensional and often turbulent. These hemodynamic effects may be significant contributors to the high failure rate. Our research, using computational and experimental models, considers the flow in AVFs and how the geometry may affect the development of stenosis. We are also modelling different surgical techniques that may determine which result in the most hemodynamically beneficial geometry.

AVF database

Stents

The major drawback of the AVF is that it is prone to Intimal Hyperplasia (IH) which is the situation where there is migration and proliferation of smooth muscle cells to the inner surface of the vessels. This situation leads to stenosis formation which in turn decreases the function of the AVF. One technique to remedy this situation is to implant a stent (vascular scaffolding) in the diseased region of the AVF thereby expanding the section back to the required size. For the successful stenting procedure, the stent needs to be flexible and able to curve around the anastomosis. This property of the stent not only expands the size of the vessel, but also shapes the AVF in such a way that the flow is diverted to the vein with lower obstruction.

 

To investigate this effect, computational fluid dynamic (CFD) is being conducted on patients with juxta-anastomotic stents. One of the factors of IH is the haemodynamic effect of blood. Therefore, the goal of conducting the CFD experiments is to analyse the wall shear stress and the turbulence effects in the anastomotic region of the AVF. To validate the CFD experiment, Tomographic PIV experiments using lasers will be conducted on a bench-top model of an AVF with juxta-anastomotic stenting.

 

By examining the results of the validated CFD, the target is to hone haemodynamic factors that cause the success of the juxta-anastomotic stenting technique in an AVF.

AVF Failure Prediction

Our research group is investigating the statistic methods to predict the arteriovenous fistula (AVF) failure based on the combination of existing patient’s data and computational modelling. We work closely with vascular surgeons in the Prince of Wales Hospital to study the conditions of different AVFs by scanning patients with an ultrasound imaging system. This research aims to contribute to the on-going efforts to reduce AVF failure, and to improve the quality of life of CKD patient by effectively aiding surgical planning and outcome.