Feasibility evaluation of a new pericardial bioprosthesis with dye mediated photo-oxidized bovine pericardial tissue

Background and aims of the study: In an attempt to overcome the problem of calcification of bioprostheses, a novel bovine pericardial tissue valve preserved with a non-aldehyde, dye mediated photo-oxidation process (PhotoFixTM) developed by CarboMedics, Inc. The device was evaluated by implantation in the mitral position of juvenile sheep with a mean age of 3.5 months. Materials and methods: Thirteen valves were evaluated; six experimental valves with photo-oxidized tissue, five identically designed valves with glutaraldehyde-fixed tissue, and two Carpentier-Edwards pericardial valves as controls. Results: Four of the six animals in the photo-oxidized group were free of calcification when electively sacrificed at 152 days, 152 days, one year and 1.5 years respectively. One animal was electively sacrificed at 98 days. Pathologic findings indicated minimal calcification of the valve due to uneven stress distribution from two bent stent posts that most likely occurred during surgical implantation, but the device was still functional. The sixth animal with photo-oxidized tissue died at 131 days due to massive calcification of a single leaflet. There was no pathologic evidence of infection. Explants at five months from additional and still continuing sheep studies per FDA guidelines have not reproduced single leaflet calcification in over forty explanted valves with photo-oxidized tissue. The glutaraldehyde-fixed valves all exhibited some calcification at explant; two of these animals died early due to the mineralization. Both control animals with Carpentier-Edwards valves died early from mitral stenosis due to extensive device calcification. Conclusions: The fact that four of six valves with photo-oxidized tissue remained free of any signs of calcification for up to 1.5 years, while none of the other valves did, suggests that photo-oxidation is a promising method of preserving and fixing tissue for use in bioprostheses. These results suggest that photo-oxidized bioprosthetic valves may be clinically valuable and warrant further study.