Stented pulmonary valve allografts as tricuspid valve substitutes in sheep: Their macroscopic and microscopic decline

Abstract

In sheep, stented pulmonary semilunar valves have been allografted as tricuspid valve substitutes and their biological behaviour has been followed postoperatively. Whereas there was initial pleasing function with normal cusp competence, by day 102 the cusps had retracted to partial incompetence. This process of valve decline was accentuated by day 150, and by day 241 was complete. Histological studies at day 150 showed cusp foreshortening, with scant nuclei and collagen looser than normal. These findings suggested that the mechanism causing the valve decline was a host to foreign body reaction rather than the usual histological pattern of graft rejection.Human aortic valve allografts are frequently used in clinical cardiac surgery as aortic valve substitutes and have given excellent long-term palliation at this site (Brandt, Roche, Barratt-Boyes, and Lowe, 1969;Ross and Yacoub, 1969). Nevertheless there is evidence that, over a period of time, degenerative changes can occur, with risk to the recipient (Smith, 1967) and the need for further replacement. Such changes, predicted as possible by Brock (1968), occur in sheep within five to seven months of implantation (Borrie and Hill, 1968