A nonlinear anisotropic model for porcine aortic heart valves

The anisotropic property of porcine aortic valve leaflet has potentially si gnificant effects on its mechanical behaviour and the failure mechanisms, H owever. due to its complex nature, testing and modelling the anisotropic po rcine aortic valves remains a continuing challenge to date. This study has developed a nonlinear anisotropic finite element model for porcine heart va lves. The model is based on the uniaxial experimental data of porcine aorti c heart valve leaflet and the properties of nonlinear composite material. A finite element code is developed to solve this problem using the 8-node su per-parameter nonlinear shells and the update Lagrangian method. The stress distribution and deformation of the porcine aortic valves with either unif orm and non-uniform thicknesses in closed phase and loaded condition are ca lculated. The results showed significant changes in the stress distribution s due to the anisotropic property of the leaflets. Compared with the isotro pic valve at the same loading condition. it is found that the site of the p eak stress of the anisotropic leaflet is different, the maximum longitudina l normal stress is increased, but the maximum transversal normal stress and in-plane shear stress are reduced. We conclude that it is very important t o consider the anisotropic property of the porcine heart valves in order to understand the failure mechanism of such valves in vivo. (C) 2001 Elsevier Science Ltd, All rights reserved.