Lingling Wei ^1* Ke Hu ¹ Jiaqiu Wang ² Shuang Zhang ¹ Xiaoxiao Yang ¹ Yuanli Chen ¹ Chenshu Li ³ Xinwu Lu ⁴ Kaichuang Ye ⁴ Peng Qiu ^4* Yanqing Zhan ^5,6*

• ¹ Key Laboratory of Metabolism and Regulation for Major Diseases of Anhui Higher Education Institutes，Hefei University of Technology, Hefei, Anhui Province, China
• ² School of Engineering, London South Bank University, London, England, United Kingdom
• ³ Department of Vascular Surgery, The Affiliated Chuzhou Hospital of Anhui Medical University, Chuzhou, China
• ⁴ Department of Vascular Surgery, Shanghai Ninth People’s Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai, China
• ⁵ Department of General Surgery, First Affiliated Hospital of Anhui Medical University, Hefei, Anhui Province, China
• ⁶ Anhui Public Health Clinical Center, Hefei, Anhui Province, China

Iliac Vein Compression Syndrome (IVCS) is a common risk factor for deep vein thrombosis in the lower extremities. The objective of this study was to investigate whether employing a porous medium model to simulate the compressed region of an iliac vein could improve the reliability and accuracy of Computational Fluid Dynamics (CFD) analysis outcomes of IVCS. Pre-operative Computed Tomography (CT) scan images of patients with IVCS were utilized to reconstruct models illustrating both the compression and collateral circulation of the iliac vein. A porous medium model was employed to simulate the compressed region of the iliac vein. The agreement of times to peak between discrete phase particles in CFD analysis and contrast agent particles in Digital Subtraction Angiography (DSA) were compared. Furthermore, a comparison was made between the CFD analysis results that incorporated the porous media and those that did not. The results revealed that in the CFD analysis incorporating the porous media model, more than 80% of discrete phase particles reached the inferior vena cava via collateral circulation. Additionally, the concentration variation curve of discrete phase particles demonstrated a high concordance rate of 92.4% compared to that obtained in DSA. In comparison to CFD analysis conducted without the porous medium model, the incorporation of the porous medium model resulted in a substantial decrease in blood flow velocity by 87.5% within the compressed region, a significant increase in pressure gradient of 141 Pa between the inferior vena cava and left iliac vein, and a wider distribution of wall shear stress exceeding 2.0 Pa in collateral vessels rather than in the compressed region. The study suggests that the introduction of a porous medium model improves the hemodynamic analysis of patients with IVCS, resulting in a closer alignment with clinical observations. This provides a novel theoretical framework for the assessment and treatment of patients with IVCS.