Aortic Valve Mechanics Part II: A Stress Analysis of the Porcine Aortic Valve Leaflets in Diastole

Abstract

The stress analysis of the porcine aortic valve leaflets in diastole at 80 mm Hg pressure in-vitro is presented. Incorporation of local geometrical asymmetry, material inhomogeneity, anistropy and non-linearity are applied. The stress theory used is a modified form of the thin membrane stress theory for a homogeneous linearly elastic and orthotropic lamina. Modifications are made so that the Hooke's law constitutive equations of stress may be applied to the inhomogeneous, non-linearly elastic and orthotropic thin (membrane) aortic valve leaflets.

Stress calculations are made on the premise that the valve is in pre-transition (i.e. low elastic modulus) in the circumferential direction and post-transition (i.e. high elastic modulus) in the radial direction. It is shown that s`<sub>CIR</sub> < 1 gm/mm<sup>2</sup>, and for most of the noncoronary leaflet, 0 < s`_RAD < 30 gm/mm². The areas of highest stress concentrations are in the areas of mutual leaflet coaptation near the Node of Arantii. A progressive increase of radial stresses from the sinus-annulus edge toward the node is observed.