Influence of intraluminal thrombus topology on AAA passive mechanics

An intraluminal thrombus (ILT) is found in most AAAs of clinically relevant size. Even though some studies seem to indicate a protective role of the ILT against AAA rupture, there is still great controversy on this regard. In addition, patient-specific AAA models are generated from gated medical images in which the artery is under pressure. Identification of the AAA zero pressure geometry would allow for a more realistic estimate of the aneurysmal wall mechanics and a better understanding of the role of the ILT. This study looks into the influence of the ILT on patient specific AAA accounting for the zero pressure geometry. Ten patient specific AAA of similar maximum diameter (4.8-5.2cm) and ILT volume were considered. For the stress analysis, the arterial wall is modeled as an anisotropic hyperelastic solid. Our results suggest that the geometrical configuration of the ILT relative to the arterial wall may be an influential factor not only on the ensuing peak wall stress, but also on its location within the lesion. The effects of the ILT topology are enhanced when the zero pressure configuration of the lesion is accounted for, where as the location of the peak wall stress in the lesion corresponds to the region of minimal ILT thickness. These suggest that the topology of the ILT, which greatly influence the zero-pressure geometry of the AAA, affects the stress field at the systolic pressure on AAA.