Computational predictions of damage propagation preceding dissection of ascending thoracic aortic aneurysms

Abstract

Dissections of ascending thoracic aortic aneurysms (ATAAs) cause significant morbidity and mortality worldwide. They occur when a tear in the intima-media of the aorta permits the penetration of the blood and the subsequent delamination and separation of the wall in 2 layers, forming a false channel. To predict computationally the risk of tear formation, stress analyses should be performed layer-specifically and they should consider internal or residual stresses that exist in the tissue. In the present paper, we propose a novel layer-specific damage model based on the constrained mixture theory, which intrinsically takes into account these internal stresses and can predict appropriately the tear formation. The model is implemented in finite-element commercial software Abaqus coupled with user material subroutine. Its capability is tested by applying it to the simulation of different exemplary situations, going from in vitro bulge inflation experiments on aortic samples to in vivo overpressurizing of patient-specific ATAAs. The simulations reveal that damage correctly starts from the intimal layer (luminal side) and propagates across the media as a tear but never hits the adventitia. This scenario is typically the first stage of development of an acute dissection, which is predicted for pressures of about 2.5 times the diastolic pressure by the model after calibrating the parameters against experimental data performed on collected ATAA samples. Further validations on a larger cohort of patients should hopefully confirm the potential of the model in predicting patient-specific damage evolution and possible risk of dissection during aneurysm growth for clinical applications.

Evaluation of Peak Wall Stress in an Ascending Thoracic Aortic Aneurysm Using FSI Simulations: Effects of Aortic Stiffness and Peripheral Resistance

“…The peak wall stress could reach values over 500 kPa at hot spots of the inner curvature. These results were also confirmed by Mousavi et al [48], who proposed a layer-specific damage model to computationally predict the risk of tear formation. Alford & Taber [51] had shown earlier that in the aortic arch, like in a torus, compared to the basal circumferential stress of a cylinder of similar diameter, the circumferential stress at the inner curvature increases while the stress at the outer curvature decreases.…”

Three-dimensional numerical simulation of soft-tissue wound healing using constrained-mixture anisotropic hyperelasticity and gradient-enhanced damage mechanics

“…Mesh-dependence issues are addressed by a non-local gradient-enhanced approach and a new adaptive fibre deposition approach has been integrated into the non-local healing model. Important developments are currently in progress for applying the proposed model to different applications, such as balloon angioplasty [45] or prediction of aneurysm rupture [46]. Competing interests.…”

In vitro histomechanical effects of enzymatic degradation in carotid arteries during inflation tests with pulsatile loading

“…Damage has been a topic of intense research in computational mechanics of soft tissues and arteries [29]- [35]. However, authors usually investigated mechanically induced damage in situations of overloading preceding rupture [36]. In aneurysms, damage would rather be induced chemically and occur progressively.…”