Failure properties of intraluminal thrombus in abdominal aortic aneurysm under static and pulsating mechanical loads

Abstract

ILT tissue is vulnerable against fatigue failure and shows significant decreasing strength with respect to the number of load cycles. Hence, after a reasonable time of pulsating loading ILT's strength is far below its ultimate strength, and when compared with stress predictions from finite element (FE) studies, this indicates the likelihood of fatigue failure in vivo. Failure within the ILT could propagate towards the weakened vessel wall behind it and could initialize AAA failure thereafter.

Biomechanical rupture risk assessment of abdominal aortic aneurysms based on a novel probabilistic rupture risk index

“…Stiffness decreases from the luminal to the abluminal site isotropic, hyperelastic derived from uniaxial tensile tests [40] reflecting mean population data. Stiffness decreases from the luminal to the abluminal site wall thickness considers wall thinning behind a thick ILT layer [37] spatially constant and lognormal distribution [7] residual stress in the FE reference configuration implicitly accounted by the (about) homogeneous wall stress that is predicted by a single FE across the wall implicitly accounted through wall stress homogenization at MAP through volumetric tissue growth [13] loading for rupture risk required.…”

“…tri-linear and constant interpolations for displacements and the hydrostatic pressure, respectively [38]. The model assigned isotropic constitutive descriptions for the aneurysm wall [39] and the ILT, which gradually decreased in stiffness from the luminal to the abluminal sites [40]. In addition, the FE model was fixed at the levels of the renal arteries and the aortic bifurcation, and the CT-A-recorded geometry was regarded as stress-free reference configuration.…”

“…In addition, c i are stress-like material constants set to c 1 ¼ 5 kPa, c 2 ¼ 0, c 3 ¼ 0, c 4 ¼ 2200 kPa and c 5 ¼ 13 740 kPa, in order to capture AAA wall mean population properties [20]. In contrast to the aneurysm wall, the ILT exhibits a much more linear stress-strain response [40,44], which is nicely captured by the isotropic Ogden-like [45] strain energy density function…”

“…In order to compute PRRI according to equation (2.7), both the wall strength distribution r Y and the PWS distribution r PWS are [40] reflecting mean population data. Stiffness decreases from the luminal to the abluminal site isotropic, hyperelastic derived from uniaxial tensile tests [40] reflecting mean population data.…”

Multifactorial Relationship Between 18 F-Fluoro-Deoxy-Glucose Positron Emission Tomography Signaling and Biomechanical Properties in Unruptured Aortic Aneurysms

“…Aortic geometry can be used for finite element simulations (FES) 11,12 providing, among other estimates, wall stress. Before rupture occurs, wall stress is involved in aneurysmal expansion and remodeling; the latter triggers and amplifies numerous biological mechanisms that may result in apposition of an intraluminal thrombus with its own biomechanical 13 and biological characteristics. [14][15][16][17] The biological activity of the aortic wall can be evaluated indirectly through energy consumption using 18 F-fluoro-deoxy-glucose ( 18 F-FDG) as a tracer for positron emission tomographic (PET) imaging.…”