Endotension Distribution in Finite Element Models of Abdominal Aortic Aneurysm Following Endovascular Exclusion

Purpose: Endotension has been implicated in complications following the endovascular repair of abdominal aortic aneurysm (AAA) such as continued AAA expansion and rupture, proximal aneurysm neck dilation, and endovascular graft migration. To begin to evaluate the role of endotension in the mechanisms of post-repair problems, the magnitude and distribution of endotension in an excluded aneurysm must be understood. The purpose of this study is to determine how endotension is distributed throughout excluded aneurysms without endoleak. Methods: Computational models of AAA were constructed using CT data of three experimental AAA models created from canine aortic tissue. Finite element analysis was used to simulate blood pressure loading and compute the resulting mechanical stress throughout the aneurysm. The computed stress patterns were used to evaluate how endotension is distributed throughout the aneurysm. Comparison of results between the computational and experimental models was made possible through simulating the experimental models with the computational models. Results: Peak arterial wall stresses occurred at the ends of the aneurysm where the wall was in close proximity to the endograft. Conversely, the lowest wall stresses were computed at the bulge of the aneurysm where the wall was farthest from the graft. Peak aneurysm sac (AS) stresses were higher near the endograft than at the wall. The lowest AS stresses occurred near the wall at the bulge of the aneurysm. Peak endograft stresses occurred at regions on the graft corresponding to the bulge of the aneurysm where the wall was farthest away. The lowest endograft stresses were computed at the ends of the endograft where the wall and graft were in close proximity. Conclusions: Endotension is a real phenomenon that occurs in absence of endoleak. Endotension in the aneurysm sac and wall is not uniformly distributed and attenuates with distance from the endograft. Conversely, endotension in the endograft is lowest where the wall is in close proximity. These results and conclusions complemented those of the experimental study of endotension.