Effects of the Haemodynamic Stimulus on the Location of Carotid Plaques Based on a Patient-Specific Mechanobiological Plaque Atheroma Formation Model.

Patricia Hernández-López,Estefanía Peña,Miguel Martínez,Myriam Cilla

doi:10.3389/fbioe.2021.690685

Abstract

In this work, we propose a mechanobiological atheroma growth model modulated by a new haemodynamic stimulus. To test this model, we analyse the development of atheroma plaques in patient-specific bifurcations of carotid arteries for a total time of 30 years. In particular, eight geometries (left or right carotid arteries) were segmented from clinical images and compared with the solutions obtained computationally to validate the model. The influence of some haemodynamical stimuli on the location and size of plaques is also studied. Plaques predicted by the mechanobiological models using the time average wall shear stress (TAWSS), the oscillatory shear index (OSI) and a new index proposed in this work are compared. The new index predicts the shape index of the endothelial cells as a combination of TAWSS and OSI values and was fitted using data from the literature. The mechanobiological model represents an evolution of the one previously proposed by the authors. This model uses Navier-Stokes equations to simulate blood flow along the lumen in the transient mode. It also employs Darcy's law and Kedem-Katchalsky equations for plasma and substance flow across the endothelium using the three-pore model. The mass balances of all the substances that have been considered in the model are implemented by convection-diffusion-reaction equations, and finally the growth of the plaques has been computed. The results show that by using the new mechanical stimulus proposed in this study, prediction of plaques is, in most cases, better than only using TAWSS or OSI with a minimal and maximal errors on stenosis ratio of 2.77 and 32.89 %, respectively. However, there are a few geometries in which haemodynamics cannot predict the location of plaques, and other biological or genetic factors would be more relevant than haemodynamics. In particular, the model predicts correctly eleven of the fourteen plaques presented in all the geometries considered. Additionally, a healthy geometry has been computed to check that plaque is not developed with the model in this case.

Highlights

Atherosclerosis is a disease that causes the formation of atheroma plaques in arterial walls
The second mechanical stimulus that we considered is OSI: FIGURE 4 | Correlation between the shape index and time average wall shear stress based on experimental data from Levesque et al (1986) (A) and between the shape index and oscillatory shear index based on data from Sáez et al (2015) (B)
It is worth highlighting that atheroma plaques are usually eccentric, and this feature cannot be captured with 2D axisymmetric models

Summary

Introduction

Atherosclerosis is a disease that causes the formation of atheroma plaques in arterial walls. The effect of atheroma plaques is that the thickness of the arterial wall increases-due to an accumulation of some substances such as low density lipoproteins (LDL) and foam cells (FC) in it-and, the lumen area decreases and blood cannot flow properly. It can derive in several events, such as heart attacks, ischaemias or strokes, and currently it is one of the main causes of mortality in developed countries (Gaziano and Gaziano, 2012). These mechanical stimuli can depend on several factors such as cyclic stretches, cardiac cycle, geometry of the arteries and oscillatory shear stress (Ohayon et al, 2011)

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Conclusion