Mechanical Factors in the Degeneration of Porcine Bioprosthetic Valves: An Overview

Predilection of certain sites of the porcine bioprosthetic valve (PBV) leaflets to calcification and tissue disruption has provoked suggestions that design factors and mechanical stresses may be major reasons leading to degeneration. In recent years, computer based numerical models of PBVs have shown a close association between sites of leaflet calcification and disruption and sites of leaflet stress concentration. These numerical models have also provided a means through which methodical design optimization can be carried out. Increasing stent flexibility, for instance, was shown to lead to an overall reduction of mechanical stresses on the PBV leaflets. Reducing the stent height, on the other hand, was accompanied by an undesirable increase of overall leaflet stresses. Despite encouraging work in this field, more research is needed to further elucidate means by which the structural integrity of bioprosthetic valves can be preserved through a minimization of the adverse effects of mechanical stresses.