A study of the solid and fluid mechanics of atherosclerotic plaques using numerical simulations

Alegre Martínez, César (2020) A study of the solid and fluid mechanics of atherosclerotic plaques using numerical simulations. PhD thesis, University of Nottingham.

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Cardiovascular diseases are closely related to atherosclerosis, a medical condition that consists of a local narrowing of the artery diameter due to the thickening of the artery wall. This narrowing, also known as stenosis, is caused by an accumulation of fatty substances, also known as plaque, in the intima layer of the artery. One of the biggest risks is the rupture of the plaque cap, which may lead to the formation of a blood clot. If this clot moves into the circulation, it can potentially block the blood supply to key organs in the human body, leading to life-threatening conditions. Typical locations where plaque may appear are the carotid arteries in the neck, the coronary arteries in the heart, and renal arteries in the kidneys.

The main objective of this thesis is to shed light on the plaque rupture process using numerical simulations. Specifically, as stated in the title, the goal is to study the fluid and solid mechanics of atherosclerotic plaques using fluid-structure interaction. In order to do this, several models of idealised, atherosclerotic arteries are presented. The blood flow is modelled as steady, incompressible and Newtonian, whereas both linear elastic and hyperelastic behaviours are used to model the artery wall and the plaque.

The results are divided into three main chapters. First, an axisymmetric, thin-wall artery model is analysed. The primary aim is to provide an overview of the main physics that are present in this configuration. Second, a similar atherosclerotic artery is studied, including the modelling of the plaque. The stress distributions along the geometry are analysed in order to determine how the different parameters affect the stress distributions and, potentially, the location of the rupture. Finally, an eccentric, three-dimensional model is introduced. A subsequent parametric analysis is performed, including the comparison to the previous axisymmetric models. In order to perform the simulations, the commercial software COMSOL Multiphysics has been used.

Among the main conclusions, it should be highlighted that a variation of the stiffness of certain components of the plaque may change the stress distribution significantly. This can have an effect on the location of the stress peaks, hence impacting the potential location of a rupture. Other common features of a plaque, such as positive remodelling, also affect the overall levels of stress, suggesting that certain plaques are more vulnerable than those that do not present remodelling. The comparison of the three-dimensional to the axisymmetric models showed that there are general features that can be observed with the simpler, axisymmetric models. However, some particular traits of the eccentric plaques were only observed in the three-dimensional configurations.

Item Type: Thesis (University of Nottingham only) (PhD)
Supervisors: McNally, Donal
Choi, Kwing-So
Tammisola, Outi
Keywords: atherosclerosis, fluid-structure interaction, plaque rupture, stress distributions, stenosis, fluid mechanics
Subjects: Q Science > QC Physics > QC120 Mechanics
R Medicine > RC Internal medicine
Faculties/Schools: UK Campuses > Faculty of Engineering
UK Campuses > Faculty of Engineering > Department of Mechanical, Materials and Manufacturing Engineering
Item ID: 59714
Depositing User: Alegre Martínez, César
Date Deposited: 21 Nov 2023 11:23
Last Modified: 21 Nov 2023 11:42
URI: https://eprints.nottingham.ac.uk/id/eprint/59714

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