A STRESS ANALYSIS OF THE PORCINE AORTIC VALVE LEAFLETS IN DIASTOLE By

A stress analysis of porcine aortic valve leaflets in diastole at 80 mm. Hg. in-vitro is presented. Incorpora tions of local surface geometry, leaflet material inhomoge neity, anisotropy 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 linear Hooke's Law 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 diastolic valve leaflets at 80 mm. Hg. are in pre-transition (that is, characterized by a small elastic modulus) for the circumferential direction, and in post-transition (that is, characterized by a large elastic modulus) for the radial direction. Circumferential stresses are calculated to be relatively negligible; they are estimated to be less than 21 gm/mm • Radial stresses for the non coronary leaflet lie primarily in the 0 to 20 gm/mm2 range. The regions of the largest stress concentrations are in the areas of mutual leaflet coaptation, especially near the Nodes of Aranti. A progressive increase of the radial stresses from th e sinus iii annulus edges toward the coaptation edges of the leaflets is also observed. Based on the one valve report ed, it appears that the left coronary leaflet is the highest stressed and the right coronary leaflet is the least stressed. Central leaflet radial stresses for the right coronary leaflet ar