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Fluid-Solid-Growth model of thrombus deposited Abdominal Aortic Aneurysm ​

Abdominal aortic aneurysm (AAA) is widespread disease in the overall population and more and more effort is being put into its treatment. The majority of AAAs harbor intraluminal thrombi (ILT), which has biochemomechanically active role in growth and remodeling (G&R) of AAA [1] and shows diverse effects on the AAA enlargement. ILT decreases peak wall stress but on the other hand biochemically degrades and weakens the wall. The model will couple hemodynamics with growth of AAA with ILT, and will consider thrombus complex mechanical effects. Knowing the right model of AAA, ILT growth and hemodynamics is of great importance because it allows broaden understanding of the further disease course. Bloodflow through AAA is directly related to ILT formation, and computational fluid dynamics (CFD) simulations outcome is directly used to determine whether an ILT will be deposited (figure 1.), as well as to predict the location and amount of its accumulation. Thrombus accumulation is predicted based on time averaged wall shear stress [2] on luminal surface. Bloodflow model plays crucial role because ILT settles differently compared to non-fluid G&R models. Both G&R theory and CFD simulations are run iteratively and represents the right and realistic behavior of blood vessel system, known also as fluid-solid growth model. The G&R model is based on the constraint mixture theory and the theory of evolving configurations to describe changes in geometry and structure of aorta. The aortic wall is assumed to comprise of isotropic elastin, four collagen fiber families, and circumferentially oriented smooth muscle cells. The constrained mixture G&R model is implemented into finite element analysis program FEAP via subroutines for the user defined material model [3]. Augmented Lagrange method was used to obtained incompressibility. Blood was modeled as a Non-Newtonian fluid with implemented Bird-Carreau viscosity model into OpenFOAM ; a finite volume software package.

Abdominal aortic aneurysm, biomechanics, Growth and remodeling

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