Relevance of immunologic reactions for tissue failure of bioprosthetic heart valves

Abstract

The use of biologic heart valve prostheses is decreasing because of the high incidence of failure of these bioprostheses resulting from tissue degeneration or tearing. Immunologic reactions might play a decisive role in this process. The present experimental and clinical studies were conducted to investigate the relevance of immunologic reactions to the tissue failure of glutaraldehydetanned bovine pericardial and porcine valves. Specimens of the two different types of valve material were implanted in the abdominal muscles of rats. Enzyme-linked immunosorbent assays and tritiated thymidine incorporation tests were performed to detect specific antibodies and activated T cells. All specimens were studied histologically. Identical enzyme-linked immunosorbent assays and tritiated thymidine incorporation tests were performed in 29 patients with bioimplants and in 48 controls. Twenty explanted bioprostheses were investigated using histologic and immune histologic methods. The results of the enzyme-linked immunosorbent assays and lymphocyte proliferation tests showed that glutaraldehyde-tanned bovine pericardial valves can provoke cellular and humoral immunologic reactions in rats and human beings. In explanted bovine valves, macrophages were found invading and degrading implant collagen, starting from surface lesions. The combination of the formation of mechanical lesions, the development of cellular infiltrates, and collagen disruption strongly indicates that initial surface lesions initiate the immunologic reactions in bovine pericardial valves as the result of the exposure of incompletely tanned collagen. These immune responses might accelerate tissue degeneration. Porcine valves do not provoke immunologic reactions.