Fluid-Structure Interaction in a patient-specific abdominal aortic aneurysm: Effects of wall material model and heterogeneity on risk of rupture

Rupture of abdominal aortic aneurysm is a result of the relatively complex hemodynamic forces that are exerted along the arterial walls. In the present study, numerical simulations of blood flow in a patient-specific model are performed employing the fluid-structure interaction method. The aneurysm model is reconstructed from CT angiographic scans from a patient diagnosed with abdominal aortic aneurysm, which also contains an intraluminal thrombus. Both isotropic and anisotropic material models are considered for arterial wall. In particular, the effects of arterial wall heterogeneity with respect to its material model are examined. Results indicate that unlike the computational solid stress method, which exerts the peak systolic pressure to the inner surface of the arterial wall, FSI method predicts the time of peak wall stress between the times of peak systolic velocity and pressure. Results also indicate that the isotropic material model with uniform wall thickness as compare to the anisotropic material model with variable wall thickness significantly underestimate wall stresses. The peak wall stress in all models are located somewhere on the posterior wall near the maximum diameter of AAA and the extent of the region of higher wall stresses are larger in models with variable wall thickness as compared to the uniform wall thickness. This fact along with the higher values of wall stress for variable wall thickness models, increase the rupture risk of the variable wall thickness model as compared to the models with uniform wall thickness.