BIOSA bileaflet pericardial valve: experimental study in sheep model

BIOSA is a single sheet, two-cuspal-shaped ("bileaflet") glutaraldehyde fixed bovine pericardial valve prosthesis (BP), designed to minimize stress and prevent mechanical failure. We tested this device in the adult sheep model.

Seven BIOSA and two Baxter Carpentier-Edwards (Perimount) pericardial BPs, 25 mm in size, were implanted in the tricuspid position of adult sheep. A mid term BIOSA explant (81 days) died of infective endocarditis. The remaining BPs were divided in three early explants (0-3 days: two BIOSA and one Perimount) and five late explants (162-189 days: four BIOSA and one Perimount). Protocol of the study included gross examination, mammography X-ray (score 0-4), histology, scanning (SEM) and transmission (TEM) electron microscopy and atomic absorption spectroscopy.

(a) Early explants: The mesothelium was detached, collagen-elastic fibers and pericardiocytes of the fibrosa showed optimal preservation. Calcium content in BIOSA BPs was 6.22 mg/g dry weight (mean) versus 7.75 mg/g of the Perimount BP. (b) Late explants: At naked eye all BPs showed regular cusp pliability and coaptation, without tears, perforations, fibrous pannus or calcific deposits. X-ray was either negative (three BPs) or exhibited score 1 (two BPs). Microscopic features were excellent both in terms of collagen-elastic fibers preservation and absence of inflammation. The calcium content was 4.95 mg/g dry weight (mean) in BIOSA BPs versus 5.29 mg/g in the Perimount BP.

Tissue characteristics of BIOSA BPs were optimal, without difference with Perimount BPs and in this animal model no case of structural valve deterioration occurred in the long term.