Comparison of the compressive buckling of porcine aortic valve cusps and bovine pericardium.

BACKGROUND AND AIMS OF THE STUDY: Compressive buckling at sites of sharp leaflet flexure has been implicated as a mechanism of failure in porcine xenografts. The potential for such buckling to cause damage in new-generation pericardial valves, however, has not been examined.
METHODS: Clinical-grade bovine pericardium fixed in 0.625% glutaraldehyde was cut into 5 mm-wide strips. Fresh porcine aortic valve leaflets were fixed flat in 0.625% glutaraldehyde and 5 mm-wide circumferential strips were cut. These tissues were bent to various curvatures, held bent with sutures, histologically processed, and sectioned and stained with hematoxylin and eosin. Images of the specimens were acquired by computer and the depth of compressive buckling, thickness of the specimen, and local curvature were measured.
RESULTS: Porcine tissue showed a progressive increase in depth of buckling as both thickness and curvature increased, while bovine pericardium had minimal buckling at all curvatures. Porcine tissues buckled to a mean (+/- SEM) fractional depth of 0.23+/-0.012 while bovine pericardium buckled to only 0.09+/-0.006.
CONCLUSIONS: These data suggest that the internal fibrous structure of bovine pericardium may tolerate high bending curvatures better than porcine aortic valve leaflets when stiffened and cross-linked with glutaraldehyde. This may explain the apparently good durability of current generation pericardial valves.