Investigation on regional variation of intraluminal thrombus: A mechanical and histological study

The abdominal aortic aneurysm is an irreversible dilatation of the artery and when this pathology is localized in the aortic district, the intraluminal thrombus ( ILT) is present in approximately 75% of cases. The rupture risk of AAA is thought to be associated with increased levels of wall stress. In recent decades, finite element analysis (FEA) have been used to predict wall stresses in a patient- specifi c, noninvasive manner. However, FE simulations are mainly based on homogeneous behavior for ILT material. The purpose of this work was to investigate the biomechanical behavior of ILT and to derive an appropriate constitutive relation for ventral and posterior regions. Uniaxial tensile tests were carried out and histological investigations were performed on four fresh thrombi to correlate with the change in the mechanical properties. A second- order polynomial, large- strain, hyperelastic constitutive model was developed and used to fit the uniaxial tensile testing data for determination of the material parameters. Our results indicate that the microstructure of ILT differs between the ventral and dorsal region, with the area region characterized by a nonlinear behavior and the lateral posterior area stiffer than the budge region. The peak stretch values were (mean +/- SEM) 1.24 +/- 0.04 and 1.1 +/- 0.09 for the ventral and lateral posterior area of the ILT, respectively. The material models for the thrombi are in excellent agreement with the experimental data.