Chronic kidney disease (CKD) affects 10% of Australian adults and attributes to 1 in 9 Australian deaths 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 in the patient's arm to serve as the blood access point and facilitate the increased flow through to 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 characterized with unusually high flow as well as three-dimensional and often turbulent features. These hemodynamic effects may adversely contribute to the high failure rate. Our research, using computational and experimental models, investigates these flow features in AVFs and how they are related to the the geometry and the development of stenosis. We are also modelling different surgical techniques to better understand the development of the most hemodynamically beneficial geometry.
Tomographic PIV measurement
The major drawback of the AVF is that it is prone to Intimal Hyperplasia (IH), a thickening of the vessel walls as smooth muscle cells migrate and proliferate at the inner surface of the vessels. This situation leads to stenosis formation (narrowing of the vessel) 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 to expand 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 (branching corners). 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 contributing factors to IH is the haemodynamic effect of blood. Therefore, the CFD is to used to analyse the flow features such as wall shear stress and the turbulence effects in the anastomotic region of the AVF. To validate the CFD experiment, tomographic PIV experiments using lasers are 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
In addition, our research group is also 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.