The arteriovenous fistula (AVF) is commonly faced with stenosis at the juxta-anastomotic (JXA) region of the vein. Implantation of a flexible nitinol stent across the stenosed JXA has led to the retention of functioning AVFs leading to the resulting AVF geometry being distinctly altered, thereby affecting the haemodynamic environment within it. In this study, large eddy simulations of the flow field within a patient-specific AVF geometry before and after stent implantation were conducted to detail the change in flow features. Although the diseased AVF had much lower flow rates, adverse flow features, such as recirculation zones and swirling flow at the anastomosis, and jet flow at the stenosis site were present. Larger velocity fluctuations (leading to higher turbulent kinetic energy) stemming from these flow features were apparent in the diseased AVF compared to the stented AVF. The unsteadiness at the stenosis created large regions of wall shear stress (WSS) fluctuations downstream of the stenosis site that were not as apparent in the stented AVF geometry. The larger pressure drop across the diseased vein, compared to the stented vein, was primarily caused by the constriction at the stenosis, potentially causing the lower flow rate. Furthermore, the WSS fluctuations in the diseased AVF could lead to further disease progression downstream of the stenosis. The change in bulk flow unsteadiness, pressure drop, and WSS behaviour confirms that the haemodynamic environment of the diseased AVF has substantially improved following the flexible stent implantation.

动静脉瘘（AVF）通常面临静脉近吻合（JXA）区域的狭窄。在狭窄的 JXA 上植入柔性镍钛合金支架可以保留功能性 AVF，从而导致 AVF 的几何形状明显改变，从而影响其内部的血液动力学环境。在本研究中，对支架植入前后患者特定 AVF 几何形状内的流场进行大涡模拟，以详细说明流动特征的变化。尽管患病的 AVF 的流速要低得多，但仍存在不良的血流特征，例如吻合口处的再循环区和旋流以及狭窄部位的射流。与支架 AVF 相比，患病 AVF 中这些流动特征引起的更大的速度波动（导致更高的湍流动能）是明显的。狭窄处的不稳定性在狭窄部位下游产生了大面积的壁剪切应力 (WSS) 波动，这在带支架的 AVF 几何形状中并不明显。与支架静脉相比，患病静脉的压降较大，这主要是由狭窄处的收缩引起的，可能导致流速较低。此外，患病 AVF 中的 WSS 波动可能导致狭窄下游的疾病进一步进展。总体流量不稳定性、压降和 WSS 行为的变化证实，在植入柔性支架后，患病 AVF 的血流动力学环境得到了显着改善。