Relation Between Wall Shear Stress Topological Skeleton Descriptors and Thrombus in Abdominal Aortic Aneurysms

The Aorta Abdominal Aneurysm (AAA) is a vascular pathology characterized by progressive enlargement of the abdominal aorta. The AAA initiation is caused by degradation of the aortic wall, biochemical wall stress and inflammation with immune response. Approximately the 75% of AAAs present intraluminal thrombus (ILT), three-dimensional fibrin structures with blood proteins, blood cells, platelets and cellular debris. The role of ILT within the structural stability of AAA in relation to the risk of rupture has not been entirely clarified. In detail, some studies consider the intraluminal thrombus beneficial because it reduces the pressure-wave impact and the stresses acting on the AAA wall. Other studies suggest that ILT may deprive the aneurysm wall of oxygen and reduce the wall compliance. Thus, the purpose of the present work is to improve the current understanding of the association between local hemodynamics and thrombus in AAA models. In this regard, a marked interest has recently emerged on wall shear stress vector filed topological skeleton, due to its ability to closely reflect the presence of new-wall hemodynamic features associated with vascular pathophysiology. More in detail, the wall shear stress topological skeleton is composed by fixed points, focal points where the vector vanishes and manifolds, contraction and expansion regions connecting fixed points. Moving from this scenario, this study aims to investigate the role of wall shear stress topological skeleton in AAA progression. To do that, a recently proposed Eulerian method to analyse the wall shear stress topological skeleton is applied on personalized computational hemodynamic models of a cohort of 6 patients with AAA. In particular, here we investigate the relationship between wall shear stress topological skeleton and related descriptors and the ILT growth estimated by clinical images in follow up cases of six patients. From this study, it emerges that the ILT growth does not markedly influence the WSS topological skeleton features. Moreover, the findings of the presented study suggest that the regions at the luminal surface with high values of WSS topological skeleton descriptors seem to not favour thrombus deposition.