A new method for the preservation of aortic valve homografts

Background and aim of the study. Aortic valve homografts were treated with 50% ethanol and glycerol followed by freeze-drying (D-Hydro (TM)). Comparat ive results of fresh versus D-Hydro-treated aortic roots implanted for up t o nine months in the descending aorta of sheep with induced aortic regurgit ation (AR) are reported. Methods: Six fresh and six D-Hydro valves were implanted in 12 sheep for th ree, six and nine months, and echocardiography and pressures were taken at surgery and sacrifice. Tissue sections were stained,with hematoxylin and eo sin, von Kossa, Masson's trichrome, Movat's pentachrome, von Willebrand fac tor, CD3 (a T-cell marker) and smooth muscle alpha -actin. Results: No grafts had increased gradients after implantation, or at sacrif ice. At explantation, fresh homografts showed early pannus formation follow ed by thrombus, annular dilatation and wall calcification. Leaflets were th ickened and progressively retracted. All had severe AR. The appearance of D -Hydro-treated homografts was normal, except for mild leaflet retraction in three, resulting in AR (in two animals the induced AR had healed). Histolo gically, a T-cell-mediated reaction was evident in the fresh homografts, an d collagen distortion was noted. Calcification was present in all fresh spe cimens and was severe at nine months. D-Hydro roots showed only minor calci fication in the six-month samples. Normal collagen, and a complete layer of von Willebrand factor-stained cells were present at three months. At nine months, cell rehabitation extended for two-thirds of the leaflets (alpha -a ctin+). The inflammatory reaction was very mild, with CD3+-stained cells ab sent in most samples. Conclusion: Aortic valve homo-rafts treated with the D-Hydro freeze-drying method performed better than fresh homografts due to the absence of thrombu s and annulus dilatation, limited calcification, and rehabitation of the ao rtic wall and parts of the leaflet by myofibroblasts, as well as the presen ce of a complete endothelial layer on the aortic wall and leaflet.