Combined numerical and morphological study of the heart: development of a scalable mitral valve morphometric model and assessment of modelling criteria for the right atrium

Cruz De Oliveira, Diana Marta ORCID: 0000-0002-8151-1333 (2022). Combined numerical and morphological study of the heart: development of a scalable mitral valve morphometric model and assessment of modelling criteria for the right atrium. University of Birmingham. Ph.D.

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Abstract

Frameworks for the computational modelling of heart components are continuously evolving, either to create models in a faster manner, or to represent its components more accurately. The mitral valve on the left side of the heart, for example, has a very complex geometry, and shape alterations induced by surgical procedures affect the long-term restoration of function. While several frameworks that recreate mitral valve shape from patient-specific images have been developed, allowing for the development of computational simulations of pre- and post-repaired cases, they are not flexible enough to yield a variety of models. On the other hand, accurate computational models of the right side of the heart are lacking, and since the right heart is used as a platform for clinical treatments such as haemodialysis, the development and validation of a computational model representing its function is necessary.

The overall aim of this thesis was to develop computational modelling frameworks for two components of the heart: the mitral valve on the left side, and the right atrium on the right side.

A mathematical evaluation of mitral valve morphometry through correlation analysis and evaluation of prediction equations for its shape was performed by using imaging datasets obtained in collaboration with clinicians and from the literature. This information led to the development of a computational toolbox enabling the quick generation of anatomically accurate and clinically useful parametric models of the mitral valve. This toolbox, implemented in MATLAB, generates the mitral valve geometry and respective mesh, and assigns boundary conditions and material properties, necessary for finite element analysis.

A sensitivity analysis of boundary conditions was performed to determine their influence on mitral valve biomechanics, with the chosen conditions being incorporated in the tool. A healthy valve geometry was generated and analysed, and the respective computational predictions for valve physiology were validated against data in the literature. Moreover, two patient-specific mitral valve models including geometric alterations associated with disease were generated and analysed. Mitral valve function was compromised in both models, as given by the presence of regurgitating areas, elevated stress on the leaflets and unbalanced subvalvular apparatus forces. These results showcase the importance of a healthy mitral valve shape for adequate function; further, they demonstrate the potential of the computational toolbox, which allows for the automatic finite element analysis of the mitral valve in a variety of clinical cases, useful to study the biomechanics of patient-specific shapes.

In addition, a physiological blood flow model of the right atrium was developed and validated against data in the literature. This model was used as a simulation platform to evaluate the performance of four catheter designs for haemodialysis: while the symmetric tip had the best haemodynamic results, associated with low recirculation of flow and shear stress values, the step tip designs yielded the worst haemodynamic outcomes. The presence of side holes at the tip led to a decrease in recirculating flow, associated with improved catheter performance. The present simulation platform therefore enables the assessment of the performance of several catheter designs before their release on the market.

The work presented in this thesis bridges engineering and medicine through the development of two computational frameworks with primary clinical objectives: a computational tool for the evaluation of mitral valve biomechanics for a variety of geometries and assessment of current and novel mitral interventions; and a right atrium simulation platform which potentially highlights haemodialysis catheter design features requiring optimisation for optimal performance.

Type of Work:

Thesis (Doctorates > Ph.D.)

Award Type:

Doctorates > Ph.D.

Supervisor(s):