A study of the junction between glutaraldehyde-treated allogeneic aorta and host aorta

Background and aim of the study: Stentless aortic valve bioprostheses have become popular because of their superior hemodynamics and expected increase d durability. However, the stentless bioprosthesis differs from stented val ves in that glutaraldehyde (GA)-treated tissue is implanted in direct conta ct with the native aorta. The effect of GA-treated tissue on host tissue ha s not been reported. Methods: In order to analyze the effect of GA in the healing process, sheep descending aortic conduits treated with 0.625% GA were inserted in the des cending thoracic aorta of 10 adult sheep. The implants were removed after 4 , 5, 10, 15 15, 25, 30, 32, 60 and 120 days. The upstream and downstream ju nctions were evaluated macro- and microscopically, and by immunohistology f or smooth muscle cell a-actin and von Willebrand factor. Results: By day 60 of implantation, the GA-treated conduits were calcified. By days 60 and 120, the calcification had spread to the host aorta, and wa s seen as foci of calcification in the junctional area. Acellular areas wer e also seen in the host aorta near the anastomosis. A fibrotic layer spanni ng the abluminal aspect of the junction between the implant and host aorta was present at day 4 and continued through 120 days. This layer was charact erized by a progressive increase in collagenous matrix and cellularity, as well as new blood vessel formation. The luminal aspect of the junction had a neointimal layer of variable thickness containing alpha-actin-expressing cells covered by a monolayer of von Willebrand factor-expressing cells, see n at 15-30 days and present through 120 days. Conclusion: In our model, implanting GA-fixed tissue in direct contact with living tissues resulted in cell death and calcification of host tissue wit hin 60 days. The integrity of the junction did not appear to be compromised . This may be of interest in light of the increased popularity of the stent less aortic bioprosthesis.