Structural changes of glutaraldehyde- treated porcine bioprosthetic valves

Gross anatomic, histologic, and transmission and scanning electron microscopic observations were made of 29 bioprosthetic valves that had been implanted in patients for up to 115 months. On the basis of these morphologic data, no significant evidence of tissue rejection was seen. However, the durability of these valve bioprostheses is still questionable. Our observation primarily emphasize three factors: (1) disruption of the endothelial cell barrier and the lack of significant host endothelialization even 115 months after transplantation; (2) increased permeability that eased diffusion of circulating host plasma proteins into valve tissue, and increased activity of infiltration processes, eg. calcification and lipid accumulation; and (3) biodegradation of the collagen framework. Each of these factors may contribute further to valve dysfunction. Development of an intimal fibrous sheath seems to occur in porcine bioprostheses that have been implanted for the longest periods of time, but the rate of host tissue ingrowth varies.