High glutaraldehyde concentrations mitigate bioprosthetic root calcification in the sheep model

Background. Fixation at high glutaraldehyde (GA) concentrations mitigated b ioprosthetic calcification in the rat model. The present study intended to verify this observation in the circulatory sheep model. Methods. Porcine aortic roots were either fixed in 0.2%, 1.0%, or 3.0% GA. Eight roots per group were implanted in the distal aortic arch of sheep. Af ter six weeks and six months calcification and inflammation were quantitati vely and qualitatively assessed. Results. By increasing the GA concentration from 0.2% to 3.0%, aortic wall calcification could be reduced by 38% after 6 weeks and 34% after 6 months of implantation (p < 0.01). Mineralization coincided with the presence of e lastin although calcium was predominantly found in cell nuclei and membrane s. Leaflet calcification was absent in all groups after 6 weeks but in a fe w leaflets presented as heterogeneous, nodular spongiosa deposits after 6 m onths. Overall, differences between 0.2%-, 1.0%-, and 8.0%-fixed tissue wer e quantitative but not qualitative regarding distribution patterns. There w as no significant difference in inflammatory host reaction between all grou ps. Conclusions. We have shown in the circulatory sheep model that the anticalc ific effect of better cross-linking seems to outweigh the intrinsic pro-cal cific effect of GA accumulation in bioprosthetic aortic wall tissue. (Ann T horac Surg 2000;70:2091-5) (C) 2000 by The Society of Thoracic Surgeons.