CHANGES IN THE MECHANICAL-PROPERTIES OF BIOPROSTHETIC VALVE LEAFLETS MADE OF BOVINE PERICARDIUM, AS A RESULT OF LONG-TERM MECHANICAL CONDITIONING IN-VITRO AND IMPLANTATION IN-VIVO

The long-term performance and function of bioprosthetic valves constru cted from glutaraldehyde-fixed bovine pericardium depend on the leafle t material retaining its original properties. Prolonged mechanical con ditioning or implantation in the human body may alter the mechanical p roperties, the geometry and the function of the leaflets. Studies of t he leaflets of fatigue-cycled valves and explanted valves showed that the leaflets have changed their shape due to permanent deformation. In addition, the leaflets of the explanted valves were thickened. Examin ation of the mechanical properties of the leaflet tissue showed that t he material of both the fatigue-cycled and explanted valves had reduce d extensibility compared to the material of uncycled leaflets, which h ad not been implanted. Such changes may adversely affect the valve fun ction and may also accelerate valve failure in the long term. Analytic al description and statistical treatment of the mechanical behaviour o f the leaflet tissue showed that it was possible to discriminate betwe en implant and explant tissue and less satisfactorily between uncycled -control and fatigue-cycled tissue.