The association of bound aldehyde content with bioprosthetic tissue calcification

The rapid progression of mineralization seen in glutaraldehyde-treated valves has prompted a wide variety of secondary treatments aimed at mitigating dystrophic calcification. We tested the hypothesis that aldehyde residuals bound to bioprosthetic tissue is a significant promoter of calcification. We developed a novel assay to measure residual aldehyde functional groups and assessed aldehyde content in three different groups: glutaraldehyde-fixed tissue (Glut-only), Edwards ThermaFix™ treated tissue and Edwards RESILIA™ tissue. The amount of tissue calcification in these same groups was assessed in vivo using a well-established rabbit model, in which tissue samples were implanted intramuscularly for 60 days. The aldehyde content of the Glut-only, ThermaFix™ treated and RESILIA™ tissues were 225.7 ± 31.5, 101.9 ± 79.7 and 32.5 ± 48.4 nmol/g, respectively. The differences among all three groups were highly significant (p < 0.001, Student's unpaired t test). The median (interquartile range) calcium content of the Glut-only, ThermaFix™ treated and RESILIA™ tissues were 227.4 (221.8-243.6), 101.0 (23.05-169.6), and 10.1 (0.28-51.7) μg/mg. The differences among all three groups were highly significant (p < 0.001, Mann-Whitney U test). The results indicated that our novel assay was able to reliably measure aldehyde content in bovine pericardial tissue. Furthermore, there appeared to be a close association between aldehyde content and tissue calcium content. The processing of bioprosthetic valves to reduce their aldehyde content may offer a significant advantage in terms of reducing the potential for long-term calcification in human implants.