Blood flow dynamics in surviving patients with repaired Tetralogy of Fallot

Student thesis: Doctoral Thesis

Abstract

Tetralogy of Fallot (TOF) is a congenital heart disease that causes structural abnormalities in the pulmonary arteries, which in turn disrupt the blood flow. Surgical repair is necessary early in childhood, but chronic complications are common in the adult surviving patients. Pulmonary valve replacement is an operation performed in the repaired TOF (rTOF) patients to overcome the right ventricular overload, but the optimal timing remains a challenge. The main research question is whether the haemodynamic environment of the pulmonary junction can clarify the interplay between the upstream and downstream pulmonary vasculature. Therefore, an extensive analysis of the effect of morphological and flow characteristics in healthy and rTOF models was performed, under various boundary conditions (BCs). The effects of branch angle and origin, branch stenosis, flow splits and pulmonary resistance were investigated in idealised two-dimensional geometries, representative of healthy and rTOF cases, explaining the elevated pressure in the LPA, and clearly showing that downstream pressure and peripheral resistance alter the flow development and the flow split between the two daughter branches. Various modelling parameters were also tested, demonstrating the importance of the valve, and how it disturbs the flow patterns along the MPA. The elasticity of arterial wall had a minimal effect on the flow development while the WSS deviated based on the rheological model assumed. Finally, anatomically realistic three-dimensional models of rTOF patients and healthy volunteers were reconstructed and morphological and flow features were analysed. Higher curvature and tortuosity were correlated with more complex secondary flow patterns, and higher Reynolds and Dean numbers, with increased regions of time-averaged wall shear stress. More importantly, the importance of patient-specificity in the rTOF models, and the variability of the geometric and flow characteristics within the population was highlighted, contrary to the observations in the healthy models. The results of this work could help clinicians evaluate the haemodynamic environment in the rTOF population and potentially predict patients at higher risk, prior to the appearance of severe complications.
Date of Award1 Nov 2021
Original languageEnglish
Awarding Institution
  • University Of Strathclyde
SponsorsUniversity of Strathclyde
SupervisorAsimina Kazakidi (Supervisor) & Terry Gourlay (Supervisor)

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