The anticalcific effect of glutaraldehyde detoxification on bioprosthetic aortic wall tissue in the sheep model.
BACKGROUND
Increasing concentrations of glutaraldehyde (GA) lead to a decreased rather than increased calcification of bioprosthetic aortic wall tissue. This study determined to what extent the benefit of better cross-linking is masked by the intrinsic propensity of GA towards calcification.


METHODS
Porcine aortic roots were immediately fixed at the abattoir at three different concentrations of GA (0.2%, 1.0%, and 3.0% for 1 week at 4 degrees C). Subsequently, roots underwent a GA extraction process using high volumes of Urazole solution (acetic acid buffer, pH 4.5, 37 degrees C, 1 week) followed by NaBH4 reduction (2 days, 37 degrees C). Roots were implanted in the distal aortic arch of young sheep for 6 weeks and 6 months. Calcium analysis was quantitatively done by atomic absorption spectrophotometry and qualitatively assessed by light microscopy on Von Kossa stains.


RESULTS
There was a distinct anticalcification effect of GA detoxification after 6 weeks (56.8% to 97.9%; 95% confidence interval [CI]), which stabilized on a more moderate level after 6 months of implantation (19.1% to 31.6%; 95% CI). The most pronounced effect of GA extraction was seen in 0.2% fixed tissue, where aortic wall calcification was mitigated by 97% and 32% after 6 weeks and 6 months, respectively. Mitigation of aortic wall calcification was 71% (6 weeks) and 21% (6 months) in the 3.0% GA group. The combined effect of higher cross-link density and detoxification achieved an 82% (6 weeks) and 48% (6 months) reduction of calcium levels in the 3.0% GA group. In long-term implants (6 months), detoxification alone on top of standard 0.2% GA fixation was as effective (from 174.1 +/- 11.9 microg/mg without detoxification to 119.3 +/- 19.3 microg/mg with detoxification) as 3.0% fixation (114.8 +/- 10.0 microg/mg without detoxification to 91.3 +/- 11.5 microg/mg with detoxification).


CONCLUSIONS
We were able to determine in the circulatory sheep model to what degree the intrinsic procalcific effect of GA counteracts the protective effect of higher cross-link density. Our study also established that the effect of detoxification is particularly pronounced in commercial low-grade fixation.
Zilla
P
P
Department of Cardiothoracic Surgery, Cape Heart Center, University of Cape Town, South Africa. zilla@capeheart.uct.ac.za
Weissenstein
C
C
Bracher
M
M
Human
P
P
D000818:Animals; D001013:Aorta, Thoracic / Q000187:drug effects* / Q000601:surgery*; D001705:Bioprosthesis / Q000009:adverse effects*; D019917:Blood Vessel Prosthesis Implantation; D002114:Calcinosis / Q000188:drug therapy* / Q000209:etiology*; D003432:Cross-Linking Reagents / Q000493:pharmacokinetics*; D004195:Disease Models, Animal; D004305:Dose-Response Relationship, Drug; D019544:Equipment Failure Analysis; D005976:Glutaral / Q000493:pharmacokinetics*; D006652:Histological Techniques; D008658:Inactivation, Metabolic / Q000502:physiology*; D008955:Models, Cardiovascular; D012756:Sheep; D013997:Time Factors; D016707:Tissue Fixation; D016896:Treatment Outcome
D003432:Cross-Linking Reagents; D005976:Glutaral