Using geometry and biomechanics to understand aortic pathology and endovascular aortic repair outcomes.

Abstract

Aortic disorders such as dissections and aneurysms affect the structural integrity and strength of the body's major artery. Endovascular aortic repairs have become the preferred course of treatment for such disorders, where a cylindrical stent graft made of metal and fabric is inserted in the aorta to restrict blood flow away from the regions of disease. After endovascular repairs, unfavorable outcomes as a result of the aorta failing to remodel include endoleak, graft migration, neck dilation, graft kinking, and material fatigue. To better understand the interactions between the aorta and stent graft, we need to mechanistically understand how these different biological and synthetic surfaces couple and interact together. Our approach is to apply methods in differential geometry, finite element analysis, and computational fluid dynamics to 3D models of aortas generated from medical imaging. Our results show that there exists a geometric signature that correlates aortic size and shape with clinical outcomes. Additionally, aortas appear to undergo shape preserving growth during normal development; however, pathologic aortas grow with shape changes. For stent grafts to be effective, they must conform to the shape of the aorta and align against the aortic wall. In order to understand why endovascular aortic repairs fail, we capitalize on the enormous availability of medical imaging data on patients with aortic pathology. We hypothesize that geometric incompatibility between stent graft and aorta impacts the mechanical stability of the seal zone. By considering the geometry and biomechanics of the aorta, we hope to develop a risk-stratification and classification scheme to optimize outcomes by defining better patient selection for endovascular surgery and creating design rules for the next generation of stent grafts.