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.