ORTHOTROPIC MECHANICAL-PROPERTIES OF CHEMICALLY TREATED BOVINE PERICARDIUM

To facilitate bioprosthetic heart valve design, especially in the use of novel antimineralization chemical technologies, a thorough understa nding of the multiaxial mechanical properties of chemically treated bo vine pericardium (BP) is needed. In this study. we utilized a small an gle light scattering based tissue pre-sorting procedure to select BP s pecimens with a high degree of structural uniformity. Both conventiona l glutaraldehyde (GL) and photo-oxidation (PO) chemical treatment grou ps were studied, with untreated tissue used as the control group. A se cond set of GL and PO groups was prepared by prestretching them along the preferred fiber direction during the chemical treatment. An extens ive biaxial test protocol was used and the resulting stress-strain dat a fitted to an exponential strain energy Function. The high structural uniformity resulted in both a consistent mechanical response and low variability in the material constants. For free fixed tissues, the str ain energy per unit volume for GL treated BP was similar to 2.8 times that of PO treated BP at an equibiaxial Green's strain level of 0.16. Prestretched tissues exhibited a profound increase in both stiffness a nd the degree of anisotropy, with the GL treatment demonstrating a gre ater effect. Thus, structural control leads to an improved understandi ng of chemically treated BP mechanical propel-ties. Judicious use of t his knowledge can facilitate the design and enhanced long-term perform ance of bioprosthetic heart valves. (C) 1998 Biomedical Engineering So ciety.