Abstract

Saphenous vein graft (SVG) bypass placement is regarded as the optimal option for renal artery stenosis, which usually causes secondary hypertension and poor renal perfusion. Using computational fluid dynamics, this study aimed to investigate the underlying hemodynamic mechanism of the vein aneurysm and stenosis after aortorenal bypass surgery. Three-dimensional models were reconstructed based on computed tomographic angiography images of a 20-year-old female patient who suffered from uncontrollable hypertension using the image processing package Mimics (Materialise). The morphology and hemodynamic parameters in the healthy state, at initial presentation and at post-operative 9-month and 2-year follow-ups after surgery were analysed. The hemodynamic parameters became normal in the left and right renal arteries after bypass surgery. However, flow separation and stagnation occurred at the post-operative 9-month aorta-vein anastomosis, which caused asymmetrical flow and extremely high wall shear stress (WSS) and WSS gradients at the outflow vein tract, where the stenosis occurred 2 years later. In addition, the graft bending produced an asymmetrical flow pattern downstream. This research revealed that the abnormal hemodynamics, including flow separation and extremely high WSS values and gradients, caused by the retrograde flow of aortorenal bypass may be responsible for the SVG degeneration. In addition, flow asymmetry due to vessel bending is a potential risk factor for SVG aneurysm dilation.

中文翻译：

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纵向计算流体动力学研究狭窄和主动脉旁路的动脉瘤变性。

摘要

大隐静脉移植（SVG）旁路放置被认为是肾动脉狭窄的最佳选择，后者通常会导致继发性高血压和不良的肾脏灌注。本研究旨在利用计算流体动力学来研究主动脉旁路手术后静脉动脉瘤和狭窄的潜在血液动力学机制。使用图像处理软件包Mimics（Materialise），基于20岁女性高血压患者的X线断层血管造影图像重建三维模型。分析了健康状态，初次就诊时以及术后9个月和2年随访的形态和血液动力学参数。搭桥手术后左，右肾动脉血流动力学参数恢复正常。然而，术后9个月主动脉静脉吻合处发生血流分离和停滞，这导致血流不对称，流出静脉道的壁切应力（WSS）和WSS梯度极高，狭窄发生在2年后。另外，移植物弯曲在下游产生了不对称的流动模式。这项研究表明，由主动脉旁路旁路逆行引起的异常血液动力学，包括血流分离和极高的WSS值和梯度，可能是SVG变性的原因。此外，由于血管弯曲引起的血流不对称是SVG动脉瘤扩张的潜在危险因素。这导致了不对称流动，并在2年后出现狭窄的流出静脉道上产生了很高的壁切应力（WSS）和WSS梯度。另外，移植物弯曲在下游产生了不对称的流动模式。这项研究表明，由主动脉旁路旁路逆行引起的异常血液动力学，包括血流分离和极高的WSS值和梯度，可能是SVG变性的原因。此外，由于血管弯曲引起的血流不对称是SVG动脉瘤扩张的潜在危险因素。这导致了不对称流动，并在2年后出现狭窄的流出静脉道上产生了很高的壁切应力（WSS）和WSS梯度。另外，移植物弯曲在下游产生了不对称的流动模式。这项研究表明，由主动脉旁路旁路逆行引起的异常血液动力学，包括血流分离和极高的WSS值和梯度，可能是SVG变性的原因。此外，由于血管弯曲引起的血流不对称是SVG动脉瘤扩张的潜在危险因素。由主动脉旁路旁路逆行引起的SVG变性可能是原因。此外，由于血管弯曲引起的血流不对称是SVG动脉瘤扩张的潜在危险因素。由主动脉旁路旁路逆行引起的SVG变性可能是原因。此外，由于血管弯曲引起的血流不对称是SVG动脉瘤扩张的潜在危险因素。