title: In vivo study of lyophilized bioprostheses: 3 month follow-up in young sheep.
abstract: OBJECTIVE
  Glutaraldehyde is currently used in bovine pericardium bioprosthesis to improve mechanical and immunogenic properties. Lyophilization is a process that may decrease aldehyde residues in the glutaraldehyde treated pericardium decreasing cytotoxicity and enhancing resistance to calcification. The aim of this study is to evaluate bioprosthetic heart valves calcification in adolescent sheep and to study the potential of lyophilization as a mechanism to protect calcification.
  
  
  METHODS
  Two groups were evaluated: a control group in which a bovine pericardium prosthetic valve was implanted in pulmonary position and a lyophilized group in which the bovine pericardium prosthetic valve was lyophilized and further implanted. Sixteen sheep 6 months old were submitted to the operation procedure. After 3 months the sheep were euthanized under full anesthesia.
  
  
  RESULTS
  Six animals of the control group reached 95.16 ± 3.55 days and six animals in the lyophilized group reached 91.66 ± 0.81 days of postoperative evolution. Two animals had endocarditis. Right ventricle/pulmonary artery (RV/PA) mean gradient, in the control group, at the implantation was 2.04 ± 1.56 mmHg, in the lyophilization group, the RV/PA mean gradient, at the implantation was 6.61 ± 4.03 mmHg. At the explantation it increased to 7.71 ± 3.92 mmHg and 8.24 ± 6.25 mmHg, respectively, in control and lyophilization group. The average calcium content, after 3 months, in the control group was 21.6 ± 39.12 µg Ca+2/mg dry weight, compared with an average content of 41.19 ± 46.85 µg Ca+2/mg dry weight in the lyophilization group (P=0.662).
  
  
  CONCLUSIONS
  Freeze drying of the bovine pericardium prosthesis in the pulmonary position could not demonstrate calcification mitigation over a 3 month period although decreased inflammatory infiltration over the tissue.
authors.affiliation: State Civil Servants Hospital and Heart Institute, São Paulo, SP, Brazil. taniguchi@sbccv.org.br
authors.forename: Fábio Papa
authors.initials: FP
authors.lastname: Taniguchi
authors.forename: Marina Junko Shiotsu
authors.initials: MJ
authors.lastname: Maizato
authors.forename: Rafael Fávero
authors.initials: RF
authors.lastname: Ambar
authors.forename: Ronaldo Nogueira de Moraes
authors.initials: RN
authors.lastname: Pitombo
authors.forename: Adolfo Alberto
authors.initials: AA
authors.lastname: Leiner
authors.forename: Luiz Felipe Pinho
authors.initials: LF
authors.lastname: Moreira
authors.forename: Idágene Aparecida
authors.initials: IA
authors.lastname: Cestari
authors.forename: Noedir Antônio Groppo
authors.initials: NA
authors.lastname: Stolf
mesh_terms: D000818:Animals; D001705:Bioprosthesis / Q000009:adverse effects*; D002114:Calcinosis / Q000473:pathology / Q000517:prevention & control*; D002417:Cattle; D005404:Fixatives / Q000494:pharmacology; D005612:Freeze Drying / Q000379:methods; D005976:Glutaral / Q000494:pharmacology; D006350:Heart Valve Prosthesis / Q000009:adverse effects*; D008422:Materials Testing / Q000379:methods*; D023421:Models, Animal; D010496:Pericardium / Q000737:chemistry* / Q000648:ultrastructure; D011651:Pulmonary Artery / Q000601:surgery*; D011897:Random Allocation; D012756:Sheep; D018709:Statistics, Nonparametric
chemical_list: D005404:Fixatives; D005976:Glutaral