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Development of a novel numerical platform for the assessment of atherosclerotic plaque vulnerability

University of British Columbia

It is well known that mechanics of atherosclerotic plaques significantly depend on plaque geometry, location, composition, and loading conditions. Computational studies have shown great potential to characterize this mechanical behavior. Different types of plaque morphologies and mechanical properties have been used in two-dimensional (2D) and three-dimensional (3D) computational platforms mostly based on the finite element method to estimate the stability of rupture-prone plaques and detect their locations. It is well-known that 2D models are not reliable as they do not provide a consistent assessment on the vulnerability of plaques and are highly erroneous. 3D models offer a more effective evaluation but creating 3D models to be further assessed by computational means such as the finite element method is time-consuming. However, 2D models are easier to develop and are less time-consuming to assess. In this thesis, a novel computational platform was developed by which the plaque vulnerability is assessed using only 2D plaque models. We develop idealistic 2D models and their corresponding idealistic 3D models. The idealistic 3D models resemble the worst- and best- case scenarios for each 2D model. Using these 3D idealistic models, a standard error (SE) is estimated and then added to the peak stress values calculated earlier using 2D models. These SEs are also used to assess the probability of plaque stability. In this platform, the effect of viscoelasticity and anisotropy of the plaque composition is taken into consideration and the transmural pressure considered is similar to that of physiological conditions. Also, for the first time heart rate (HR) was introduced as a major predictor of vulnerable plaque ruptures that should be taken into account while mechanics of plaques is studied. A tunable viscoelastic constitutive material model was developed for the fibrous cap tissue in order to calculate the peak cap stress (PCS) in normal physiological conditions while HR changes from 60 bpm to 150 bpm. A critical discussion on stress distribution in the fibrous cap area is made with respect to HR. Results strongly suggest the viscoelastic properties of the fibrous cap tissue and HR together play a major role in the estimation of the PCS values. The results obtained in this thesis may provide a better understanding of the mechanics of atherosclerosis.

Text

2016-02-19

Attribution-NonCommercial-NoDerivs 2.5 Canada

http://hdl.handle.net/2429/57028

Mechanical Engineering

University of British Columbia

UBCO

http://creativecommons.org/licenses/by-nc-nd/2.5/ca/