Computational analysis to assess hemodynamic forces in descending thoracic aortic aneurysms.

Abstract

Descending thoracic aortic aneurysm (DTAA) is a life-threatening disorder, defined as a localized enlargement of the descending portion of the thoracic aorta. In this context, we develop a fluid-structure interaction (FSI) computational framework, with the inclusion of a turbulence model and different material properties for the healthy and the aneurysmatic portions of the vessel, to study the hemodynamics and its relationship with DTAA. We first provide an analysis on nine ideal scenarios, accounting for different aortic arch types and DTAA ubications, to study changes in blood pressure, flow patterns, turbulence, wall shear stress, drag forces and internal wall stresses. Our findings demonstrate that the hemodynamics in DTAA is profoundly disturbed, with the presence of flow re-circulation, formation of vortices and transition to turbulence. In particular, configurations with a steeper aortic arch exhibit a more chaotic hemodynamics. We notice also an increase in pressure values for configurations with less steep aortic arch and in drag forces for configurations with distal DTAA. Second, we replicate our analysis for three patient-specific cases (one for type of arch) obtaining comforting results in terms of accordance with the ideal scenarios. Finally, in a very preliminary way, we try to relate our findings to possible stent-graft migrations after TEVAR procedure to provide predictions on the postoperative state. KEY POINTS: This study employs computational methods to assess hemodynamic forces in descending thoracic aortic aneurysms. We consider ideal cases by varying aortic arch type and aneurysm location. Our results show: chaotic hemodynamics for steep aortic arches; increase in pressure values for less steep aortic arches; high risk of plaque deposition in the aneurysmal sac for proximal aneurysms and near the neck for distal aneurysms. We also analyse three patient-specific cases, confirming the major outcomes found for the ideal cases. We try to suggest how our preoperative findings may correlate to assess the risk of stent-graft migration of a possible TEVAR procedure.