title: Preimplant ultrastructure and calcification tendency of various biological aortic valves.
abstract: OBJECTIVE
  In recent years a number of fixation and anti-calcification methods have been developed, but little is yet known about the calcification process of biological valves. The aims of this study were to: (i) perform a systematic ultrastructural investigation on various biological valves; and (ii) determine the extent of calcification of these valves in a subcutaneous rat model.
  
  
  METHODS
  The following porcine aortic prostheses were investigated: Toronto-SPV, Intact, Freestyle, Mosaic and Hancock-II. Samples taken from the valve leaflets, and in the case of the Freestyle and Toronto-SPV valves also from the aortic wall, were examined ultrastructurally using scanning and transmission electron microscopy. Other samples were implanted subcutaneously in Wistar rats for 12 weeks. The calcium content of the samples was measured using atomic absorption spectrophotometry.
  
  
  RESULTS
  All valves examined showed a considerable loss of the endothelial cover. Significant changes in valve ultrastructure were also detected. With regard to calcium content, two valve groups could be distinguished (p <0.05): (i) those with high calcium content, e.g. Toronto-SPV and Intact (>40 mg/g dry tissue); and (ii) those with low calcium content, e.g. Mosaic, Freestyle and Hancock-II (<5 mg/g).
  
  
  CONCLUSIONS
  Fixation methods have pronounced effects on the ultrastructural integrity of bioprostheses. The degenerative calcification of bioprostheses can be effectively inhibited by glutaraldehyde-free fixation and anti-calcification treatments.
authors.affiliation: Department of Thoracic, Heart and Vascular Surgery, University of Göttingen, Germany.
authors.forename: M
authors.initials: M
authors.lastname: Mirzaie
authors.forename: T
authors.initials: T
authors.lastname: Meyer
authors.forename: P
authors.initials: P
authors.lastname: Schwartz
authors.forename: H
authors.initials: H
authors.lastname: Dalichau
mesh_terms: D000818:Animals; D001021:Aortic Valve / Q000648:ultrastructure*; D001705:Bioprosthesis; D002114:Calcinosis / Q000473:pathology* / Q000517:prevention & control; D002118:Calcium / Q000032:analysis; D005260:Female; D006350:Heart Valve Prosthesis; D019918:Heart Valve Prosthesis Implantation; D008854:Microscopy, Electron; D008855:Microscopy, Electron, Scanning; D011474:Prosthesis Design; D051381:Rats; D017208:Rats, Wistar; D013552:Swine
chemical_list: D002118:Calcium