In-vivo assessment of a photofixed bovine pericardial valve

The study aim was to assess the preclinical safety of a bioprosthetic cardiac valve in a large-animal model. The experimental pericardial valve was treated with a dye-mediated photooxidation process (PhotoFix) to enhance durability, and to reduce bioreactivity and mineralization potential.

Ten experimental (Sulzer Carbomedics PhotoFix pericardial valves, 25 mm) and three control valves (Carpentier-Edwards 2700, 25 mm) were placed in the mitral position of 13 juvenile sheep. Assessment criteria included animal survival, hematological analysis, host response, valve calcification and tissue stability.

No significant differences were seen between the two groups for hematological analysis, weight or age. Ease of surgical handling was equivalent or superior to currently available technology. The PhotoFix valves had minimal leaflet calcification (mean 0.20 +/- 0.12 microg/mg) at 150 days. Two animals implanted with control valves were sacrificed at 173 and 227 days due to poor health; the control valves had massive thrombus and extensive leaflet mineralization (mean calcium content 18.2 +/- 3.8 microg/mg). For comparison with controls, two sheep with Photofix valves were sacrificed electively at 218 and 235 days. At 235 days, the experimental valve had a surgical suture looped over one commissure, restricting the motion of two leaflets and leading to massive inflow surface thrombosis. Despite this restriction, the animal remained healthy, with no noticeable regurgitation. The mean calcium content of the 218-day experimental valve leaflets was 6.28 microg/mg. Two experimental valves remain in place for long-term evaluation.

In-vivo testing in juvenile sheep showed the PhotoFix pericardial valve to have no device-related mortality, no significant tissue degeneration, and minimal mineralization. In contrast, the control valves had significant valve mineralization and device-related morbidity.