A discrete approach for modeling degraded elastic fibers in aortic dissection

The initiation and propagation of aortic dissection have not yet been fully elucidated. An essential role is attributed to the degradation of inter-lamellar elastic fibers in the aortic media which causes a significant lowering of the radial strength. Inter-lamellar elastic fibers are aligned radially and contribute mainly to the cohesion of the lamellar units in the aortic media. Computational studies that consider these pathological findings during aortic dissection are rare. In this study, we propose a constitutive model which incorporates the degeneration of inter-lamellar elastic fibers. For this purpose, the recently introduced discrete fiber dispersion model is applied to include symmetrically dispersed inter-lamellar elastic fibers in a strain–energy function. Damaged or degraded elastic fibers are excluded from the strain–energy function by introducing a degradation parameter. Subsequently, the proposed model is implemented in a finite element program and verified with two representative numerical examples, uniaxial extension and simple shear. An aortic dissection geometry with two distinct layers, motivated from patient data, is then created to study the influence of degraded radially-directed elastic fibers on the stress distribution in an aortic dissection. In summary, the presented constitutive model is able to capture the degradation of inter-lamellar elastic fibers during aortic dissection. Moreover, the finite element analysis results of the patient-data motivated geometry suggest a possible mechanism triggering the dissection propagation.