Structural changes in a porcine xenograft after implantation for 105 months

Morphologic studies including light microscopy and transmission and scanning electron microscopy were performed on a formaldehyde-fixed porcine xenograft prosthesis that functioned well for 8 years and had been implanted for 105 months in the tricuspid valve position. It is the oldest implanted valve studied in this manner. Although all leaflets had some gross deterioration, only one had adherent thrombus. The degenerative changes in the connective tissue from all leaflets were similar to those recently reported in glutaraldehyde-fixed porcine valves implanted for shorter periods. The surfaces of the two nonthrombosed leaflets and small portions of the surface of the thrombosed leaflet were endothelized, and the endothelium appeared to have little or no effect on the degenerative changes in the subjacent connective tissue. Further, the endothelium did not extend over the examined portion of the synthetic anulus of the prosthesis, suggesting that its origin was possibly from cells circulating in the blood.