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Biomechanical behavior of carotid atherosclerosis : A numerical approch

Abstract : Numerical fluid biomechanics has proven to be an efficient tool for understanding vascular diseases including atherosclerosis. Studying mechanical phenomena taking place in carotid artery remains a scientifically relevant problem and can help clarify the association between blood flow behavior and the formation and rupture of atheromas. The presence of atheromas, usually in regions of high curvatures, led to a widely accepted hypothesis that local loads of hemodynamics play an important role in atherogenesis. It also causes alterations to the systemic behavior such as perturbations to the flow, stress distributions at the wall and particularly the Wall Shear Stress (WSS). In other words, hemodynamics influences the progression of atherosclerosis. In order to study the behavior of carotid artery, both CFD simulations and FSI simulations were performed on multiple geometrical models. The viscosity model and boundary conditions for the fluid domain were chosen by a preliminary analysis. Five structure models are taken into account: rigid walls with and without plaque, hyperelastic arterial structure without plaque and with a plaque simulated by a geometry restriction, hyperelastic structure with elastic plaque. The effects of the presence and absence of the plaque and of different geometry configurations was analyzed. WSS and blood flow parameters (pressure-velocity) were investigated at different locations of the vasculature with a special focus at the plaque and after plaque areas. Finally, a full FSI analysis was performed on a patient specific geometry and compared with the rigid wall results. The comparison between healthy and stenosed arteries showed different flow disruptions near the stenosis area resulting in a higher shear stress at the plaque zone and lower shear stress after-plaque zone. This result was observed both in the generic simplified geometry and in the patient specific geometry. The analysis of the structural response of the arterial tissue showed different displacement amplitudes between healthy and diseased arteries. It also showed a high frequency Fourier component of the displacement signal of the models stenosed artery: this signal slightly changes when the plaque mechanical properties are modified. The plaque rupture depends among others on the local WSS and the local strength of the tissue. On one hand LWSS zones are areas of vivid proliferation of atherosclerosis plaques, on the other hand the LWSS can promote inflammations and cause plaque instability too. The assessment of the vibrational behavior of the artery shows the emergence of low frequency modes when the plaque is present. The method proposed in this project is aimed to provide useful information for the future assessments of the dynamic response of carotid artery when more patient specific data is available and in-vivo experimental investigations are carried out.
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Submitted on : Thursday, September 10, 2020 - 3:09:07 PM
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Lina Zouggari. Biomechanical behavior of carotid atherosclerosis : A numerical approch. Biomechanics [physics.med-ph]. Université de Lyon; Università degli studi La Sapienza (Rome), 2019. English. ⟨NNT : 2019LYSEI116⟩. ⟨tel-02935635⟩

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