Modeling Patient-Specific Periaortic Interactions with Static and Dynamic Structures Using a Moving Heterogeneous Elastic Foundation Boundary Condition

Abstract

Perivascular support and tethering are likely relevant factors in vascular mechanics and one of the possible causes of deformational heterogeneity of the aortic wall. Besides these effects, the thoracic aorta interacts with the heart and other moving tissues and organs. We propose a generalized approach to model the effect of aortic interactions with static and dynamic perivascular structures. Periaortic interactions are modeled as a heterogeneous Elastic Foundation Boundary Condition (EFBC). This is implemented in the Finite Element model as a collection of unidimensional springs attached to the adventitial surface and a movable opposite end. An optimization algorithm iterates over the material constants and EFBC parameters to fit the simulated nodal displacements or the aortic wall to patient-specific DENSE MRI-derived displacements. We hypothesize that the adventitial load distribution that replicates the in vivo motion and deformation of the aorta is representative of the actual periaortic interactions. We study 3 aortic locations: the distal aortic arch, the descending thoracic aorta, and the infrarenal abdominal aorta. Our method reproduced the in vivo DENSE MRI-derived displacements with a median error below 30% of the pixel-size resolution (1.2–1.6 mm). The resulting average adventitial load is circumferentially and axially heterogeneous and ranged between 30 and 60% of the luminal pressure-pulse depending on the local nature of the periaortic interaction. Adequate modeling of periaortic interactions may bring a better understanding of its role in the normal and pathological function of the aorta in vivo.