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Abstract
The arteriovenous fistula (AVF) is a vasculature created for end-stage renal disease patients who undergo haemodialysis. This vasculature is often affected by stenosis in the juxta-anastomotic (JXA) region and the presence of disturbed haemodynamics within the vessel is known to initiate such diseased conditions. A novel treatment involving the implantation of a flexible stent in the JXA region has shown potential for retaining healthy AVFs. Only a limited number of experimental studies have been conducted to understand the disturbed flow conditions, while the impact of stent implantation on the haemodynamics within the AVF is yet to be explored.
The study was initiated by developing a benchtop patient-specific AVF model to conduct a Tomographic Particle Image Velocimetry (Tomo-PIV) measurement. The subsequent temporally resolved volumetric velocity field was phase-averaged to quantify fluctuations occurring over the inlet pulsatile conditions. It was noted that high turbulent kinetic energy (TKE) was generated at the JXA region.
To study the effects of the stent implantation, Large Eddy Simulations (LES) comparing the AVF geometry with and without the presence of the stent implantation were conducted. The trajectory of the flow in the stented case was funnelled within the stent encapsulated region which in turn, contained the disturbed flow within the stent lumen while mitigating the generation of turbulence. Consequently, the distribution of adverse wall shear stress (WSS) in the stented region was much lower compared to that of the `stent-absent' case.
Simulations were also conducted on the diseased patient AVF, before the stent implantation, to make an overall assessment of the effect of treatment. Larger and persistent regions of high TKE were noted in the vessel downstream of the stenosis despite the lower velocity of flow in the diseased model.
In summary, the stent implantation in the patient AVF showed the ability to funnel flow disturbances away from the vessel wall, thereby leading to lower adverse WSS distributions. The presence of the stent also mitigated turbulence generation. These findings provide valuable insight into the favourable haemodynamic effects of this novel endovascular procedure, thus, substantiating this treatment strategy to treat vascular disease in AVFs.
