Longitudinal computational fluid dynamics study of stenosis and aneurysmal degeneration of an aortorenal bypass

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ORIGINAL PAPER

Longitudinal computational fluid dynamics study of stenosis and aneurysmal degeneration of an aortorenal bypass Zhuxiang Xiong1 · Yi Wang2 · Zeyang Mou1 · Yan Li1 · Zhan Liu1 · Jun Wen3 · Ding Yuan4,5 · Tinghui Zheng1,6 Received: 16 October 2019 / Accepted: 12 March 2020 © Springer-Verlag GmbH Germany, part of Springer Nature 2020

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. Keywords  Renal artery stenosis · Saphenous vein graft (SVG) · Computational fluid dynamics (CFD) · Morphology · Hemodynamics

* Ding Yuan [email protected] * Tinghui Zheng [email protected] 1



Department of Applied Mechanics, Sichuan University, Chengdu 610065, People’s Republic of China

2



Department of Computer Science, Sichuan University of Science and Engineering, Zigong, Sichuan 643000, People’s Republic of China

3

School of Civil Engineering and Architecture, Southwest University of Science and Technology, Mianyang, Sichuan 621010, People’s Republic of China

4

Department of Vascular Surgery, West China Hospital, Sichuan University, Chengdu 610065, People’s Republic of China

5

Department of Vascular Surgery, West China Hospital, Sichuan University, No. 37 Guo Xue Xiang, Chengdu 610041, Sichuan Province, People’s Republic of China

6

No. 29 Jiuyanqiao Wangjiang Road, Chengdu 610064, People’s Republic of China









1 Introduction Renal artery stenosis usually causes secondary hypertension and poor renal perfusion, and long-term renal artery stenosis may cause uncontrolled hypertension and severe renal impairment. Three treatment options, namely