Abstract
Aortic dissection represents a serious cardio-vascular disease and life-threatening event. Dissection is a sudden delamination event of the wall, possibly leading to rupture within a few hours. Current knowledge and practical criteria to understand and predict this phenomenon lack reliable models and experimental observations of rupture at the lamellar scale. In an attempt to quantify rupture-related parameters, the present study proposes an analytical model that reproduces a uniaxial test on medial arterial samples observed under X-ray tomography. This model is composed of several layers that represent the media of the aortic wall, each having proper elastic and damage properties. Finite element models were created to validate the analytical model using user-defined parameters. Once the model was validated, an inverse analysis was used to fit the model parameters to experimental curves of uniaxial tests from a published study. Because this analytical model did not consider delamination strength between layers, a finite element model that included this phenomenon was also developed to investigate the influence of the delamination on the stress-strain curve through a sensitivity analysis. It was shown that shear delamination strength between layers, i.e. mode II separation, is essential in the rupture process observed experimentally.
Highlights
Aortic dissection, a sudden delamination of the aortic wall in its medial layer, is a lifethreatening arterial event associated with a very poor outcome, and requires rapid diagnosis and decision-making; without intervention, up to 90% of patient with acute aortic dissection die within weeks [7]
This paper follows up on a series of experimental uniaxial tests made on porcine medial aorta samples under X-ray tomography [6]
These tests observed the media at the lamellarscale during damage progression and rupture and showed that layers successively break in tension followed by a sudden delamination due to their elastic recoil
Summary
A sudden delamination of the aortic wall in its medial layer, is a lifethreatening arterial event associated with a very poor outcome, and requires rapid diagnosis and decision-making; without intervention, up to 90% of patient with acute aortic dissection die within weeks [7]. As highlighted by the review of Nienaber et al [12], dissection is usually thought to be caused by an intimal tear in which the blood rushes and propagates in the medial layer. Dissection can be initiated at the site of an intramural hemorrhage, which is thought to be less frequent. Few studies have tried to explain the microstructural phenomena occurring during initiation and propagation of dissection in the aorta. Advanced mechanical analyses of the underlying mechanisms, based on mechanical experiments as well as structural observations at the micro- and meso-scales – these two being possibly combined – would deeply improve the understanding of such fatal event and could improve clinical decision-making criteria
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