Behavior of vital and killed autologous pericardium in the descending aorta of sheep

Objectives: Cardiovascular implants of fresh autologous pericardium produce d mixed results including fibrosis with retraction or thinning and dilatati on, The reasons for these differences are unknown but may involve activatio n of cells intrinsic to the tissue implant. To better understand the behavi or of autologous pericardial implants, we studied the outcomes of vital per icardium (fresh) versus ethanol-killed pericardium, Methods: Fresh and etha nol-killed autologous pericardium was transplanted as a patch, a conduit, o r a rectangular flap bisecting the lumen in the descending aorta of sheep. The implants, recovered at 1, 5, 10, 15, and 30 days, were evaluated macros copically and microscopically and by immunohistologic studies. Results : Fr esh implants showed good preservation with fibrin deposition on day 15, Mic roscopically, cells positive for alpha-actin and von Willebrand-related ant igen appeared in the fibrin by day 10, By day 30 the flap was fibrotic and retracted whereas the patch and conduit retained their original appearance on the luminal aspect. An endothelium-like layer expressing von Willebrand- related antigen was present in the patch and conduit but absent in the flap . In contrast, the ethanol-killed implants were free of fibrin by day 10, B y day 30, there were no signs of fibrosis or retraction, and a surface laye r of cells expressing von Willebrand-related antigen, characteristic of end othelial cells, was present on all implants. All ethanol-killed implants we re repopulated by host cells. Conclusion: The transluminal flap is an inter esting model for studying the behavior of intraluminal autologous pericardi al cardiovascular implants. Killing of the pericardial implants alleviated the fibrosis and tissue retraction observed with fresh flap implants.