In-silico models of arteriovenous fistulas in patients with end-stage renal disease

Martínez Dalmau, Lídia

In-silico models of arteriovenous fistulas in patients with end-stage renal disease

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Citation

Martínez Dalmau, L. In-silico models of arteriovenous fistulas in patients with end-stage renal disease. 2023. handle: http://hdl.handle.net/10230/57937

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Abstract

End-stage renal disease (ESRD) is a life-threatening condition that affects over 10% of the global population, necessitating hemodialysis (HD) for patients awaiting a kidney transplant. The arteriovenous fistula (AVF) is the preferred access for HD treatment, but it is often prone to complications that jeopardize its effectiveness and pose serious risks like thrombosis. AVF failure primarily stems from non-maturation of the AVF and post-maturation stenosis. Previous in-silico studies have suggested that these events are influenced by changes in the vascular lumen cross-sectional area and the degree of the anastomotic angle, which could be correlated with the patient’s inflammatory state. However, literature on this subject is limited, focusing solely on individual patient-specific models in Computational Fluid Dynamics (CFD) simulations, neglecting specific boundary conditions and the patients’ health status. This study aims to establish a foundation for constructing an advanced numerical model that accounts for the clinical, hemodynamic, and morphological characteristics of patients. It includes nine patient-specific geometries, with CFD simulation results presented for three of them while the others are still being analyzed. The models were created based on Magnetic Resonance Imaging (MRI) obtained at three time periods (1 week, 1 month, and 6 months) after surgery, which are critical for understanding the development and temporal evolution of the AVF. Boundary conditions were derived from ultrasound scans taken at these specific time points. Additionally, a mathematical 3-element Windkessel model was utilized, taking into account the patient’s classification as normotensive or hypertensive to estimate its parameters. No previous study has examined such a large number of patients or conducted a comprehensive temporal follow-up while also considering the patients’ health status. Specific AVF geometries and their evolution over time were found to impact the flow characteristics in patients. The juxta-anastomotic section was identified as the area most affected by flow in cases where the angle of the anastomosis was not tortuous describing a ’U-shape’, exhibiting higher magnitude and distribution of Wall Shear Stress (WSS) and greater velocity magnitude.