Dynamical influences of different aneurysm sizes on rupture risk of abdominal aorta

The current clinical index for surgical intervention of abdominal aortic aneurysms (AAA) is mainly based on measuring its maximum diameter. However, ruptures in AAAs do not necessarily occur at this location and conditions of rupture are still unclear. This study focuses on the understanding of the aneurysms rupture mechanisms. A set of fluid-structure interaction (FSI) models is developed to investigate the AAAs expansion into low wall shear stress (WSS) regions. 3D model geometries for different clinical stages are acquired from the literature including the final stage just before rupture. Blood is simulated as non-Newtonian fluid and dymanic boundary conditions are enforced to simulate blood pulsations. Local and averaged WSS, which are the critical parameters affecting rupture conditions, are evaluated based on the computational results. It is demonstrated that both averaged and local WSS correlate well with the rapid expansion of AAA as well as with rupture locations. From the present FSI study, blood recirculation is one of the main mechanism leading to a decrease in the WSS, which significantly increase the risk of rupture. The latter agrees with the outcomes of previous studies.