The Importance of Bending Stresses in the Leaflets of Pericardial Heart Valve Substitutes

Summary

Cyclic uniaxial load tests were performed on strip specimens of chemically modified bovine pericardium. Young’s modulus and Poisson’s ratio varied with uniaxial loading. Using effective incremental representations of these parameters, a simple analysis of the cylindrical bending of a flat plate showed that, under physiological closing pressures, the bending stresses in pericardial heart valve leaflets could be substantial. Their magnitude depended on the attachment conditions of the leaflet to the stent. If the tissue was clamped between a male and female frame, then large tensions were predicted on the outflow surface and significant compressive stresses could occur on the inflow surface of the leaflet. The presence of high stresses in regions close to the stent posts may explain the cuspal tears found at these sites, during wear testing of pericardial heterografts and after clinical implantation.