On the influence of pressure drop and fluid-structure interaction on the hemodynamics of arteriovenous fistula

Chronic kidney disease (CKD) is a prevalent global health concern, affecting millions worldwide and often progressing to end-stage renal disease (ESRD), necessitating interventions like hemodialysis (HD). Arteriovenous fistulas (AVFs) are commonly created to facilitate HD due to their advantages over alternative methods. However, a significant percentage of AVFs fail to mature successfully, leading to complications. Understanding the hemodynamic factors influencing AVF outcomes is crucial, particularly in addressing issues like stenosis, intimal hyperplasia (IH), disturbed shear stress and negative remodelling.This research aims to bridge existing gaps in the numerical modelling of AVF hemodynamics, focusing on three critical areas: accurately simulating the pressure drop across the AVF anastomosis, the impact of compliance on wall shear stress (WSS)-based parameters, and the time-dependant impact of arterial flow conditions on venous material properties. The thesis includes an extensive review of existing research on AVF hemodynamics, numerical modelling techniques, and experimental methodologies, setting the stage for subsequent investigations. It validates the numerical approach through ex-vivo displacement data analysis and highlights previous validation studies adopting similar numerical methodologies, thus appropriately representing real-world conditions. The pressure distribution across AVFs at the time of surgery is assessed, revealing discrepancies between in-vivo measurements and numerical simulations. Insights gained highlight the need for improved modelling techniques to replicate realistic pressure drops accurately. Furthermore, a comparative evaluation of patient-specific computational models was conducted, comparing conventional Computational Fluid Dynamics with Fluid-Structure Interaction simulations. Highlighting the importance of personalised assessments and refined computational modelling techniques.This research also explores ex-vivo perfusion of vascular tissue as a means of analysing morphometric changes induced by controlled hemodynamics. This work underscores the time-dependent nature of venous tissue adaptation, advocating for dynamic material models in AVF simulations to accurately capture tissue responses over extended durations.Overall, this research contributes to our understanding of AVF hemodynamics and venous tissues material properties response to increased flow and pressure. Identified gaps and future research directions aim to advance the field of AVF characterisation and treatment, ultimately improving outcomes for patients with CKD and ESRD.