Different modes of degeneration in autologous and heterologous heart valve prostheses.
OBJECTIVE
This study was performed to elucidate the mechanism of primary tissue failure of bioprosthetic heart valves, which were fabricated from autologous pericardium (Autogenics). Results were compared with the degeneration pattern of heterologous pericardial bioprostheses.


METHODS
Between March 1994 and December 1996, 87 Autogenics heart valves were implanted in the aortic position. Since then, 15 valves had to be explanted due to structural deterioration. The average implant period was 33+/-8 months. All explants were examined by gross morphological evaluation and X-ray analysis to identify the failure mode of these devices. In eight explanted autologous tissue valves and six explanted heterologous pericardial bioprostheses, exact morphological evaluation was performed by scanning electron microscopy, microscopic and immunohistochemical techniques.


RESULTS
All autologous tissue valves failed due to cuspal tears localized at the commissures. Nocalcification could be detected by X-ray analysis and microscopic methods. Endothelial cell coverage was evident at the outflow surface of all autologous bioprostheses. Histological examination showed severe disintegration of the collagen fibers by insudated plasma proteins and erythrocytes, and the absence of the original fibroblasts. Collagen fibers were vigorously altered between the inner and outer stent of the Autogenics valve. In contrast, heterologous pericardial valves failed due to severe calcification of the cusps. Histological evaluation displayed invasion of macrophages and calcific deposits. The collagenous texture of the pericardial tissue was significantly better preserved compared with autologous tissue.


CONCLUSIONS
High biocompatibility of autologous tissue valves is indicated by the absence of calcium deposits, macrophages and foreign body giant cells, and the presence of endothelial cell ingrowth. Severe disintegration of autologous tissue suggests that brief immersion in glutaraldehyde generates inadequate mechanical stability of bioprosthetic heart valve material. Heterologous valves exhibit low biocompatibility but superior preservation of the collagenous biomaterial.
Grabenwöger
M
M
Department of Cardio-Thoracic Surgery, University of Vienna, Austria.
Fitzal
F
F
Gross
C
C
Hutschala
D
D
Böck
P
P
Brucke
P
P
Wolner
E
E
D000368:Aged; D000369:Aged, 80 and over; D001672:Biocompatible Materials; D001705:Bioprosthesis; D002114:Calcinosis / Q000209:etiology; D005260:Female; D006350:Heart Valve Prosthesis; D006801:Humans; D008297:Male; D008875:Middle Aged; D011475:Prosthesis Failure; D014182:Transplantation, Autologous; D014183:Transplantation, Heterologous
D001672:Biocompatible Materials