title: Percutaneous heart valve replacement: histology and calcification characteristics of biological valved stents in juvenile sheep.
abstract: BACKGROUND
  Percutaneous techniques to replace the pulmonary valve are emerging as an alternative to congenital cardiac surgical procedures. Promising experimental and early clinical results have been reported so far, focusing on technical feasibility and valved stent function. The present study aimed to describe the micropathology after experimental percutaneous valve replacement.
  
  
  METHODS
  Self-expanding nitinol stents carrying a valved bovine jugular vein were transfemorally implanted into the pulmonary position of nine sheep. After 3 months of survival, macro- and micropathological examinations were carried out using standard staining techniques and immunohistochemistry. Additionally, calcification characteristics were determined by X-ray examinations and von Kossa stainings.
  
  
  RESULTS
  Six of nine animals survived the 3-month study time with good angiographic and echocardiographic function. All valves were grossly functional at the time of explantation. Slight fibrous overgrowth was seen at the inflow portions of two valved stents. No cuspal perforations or intracuspal hematomas were observed. Light microscopy proved the absence of cellular inflammatory infiltrates in any tissue samples. The myocardium directly proximal to the stent appeared structurally normal without calcification. The overall structure of the native pulmonary artery was well preserved with few mineral deposits spread diffusely throughout the wall distal to the stent. Massive calcification appeared in the bovine jugular-vein wall together with increased numbers of T lymphocytes. Neither calcific deposits in the cusps nor extrinsic mineralization was noted.
  
  
  CONCLUSIONS
  For the first time, micropathologic evaluation of percutaneously implanted heart valves is described. The results demonstrate that calcification of valved stents occurs in the wall portions without affecting the cusps. The cardiac structures in the vicinity had normal histology without inflammation.
authors.affiliation: Department of Cardiovascular Surgery, School of Medicine, Christian-Albrechts-University of Kiel, Arnold-Heller-Str. 7, D-24105 Kiel, Germany.
authors.forename: Tim
authors.initials: T
authors.lastname: Attmann
authors.forename: René
authors.initials: R
authors.lastname: Quaden
authors.forename: Andrea
authors.initials: A
authors.lastname: Freistedt
authors.forename: Christian
authors.initials: C
authors.lastname: König
authors.forename: Jochen
authors.initials: J
authors.lastname: Cremer
authors.forename: Georg
authors.initials: G
authors.lastname: Lutter
mesh_terms: D000818:Animals; D001705:Bioprosthesis; D002114:Calcinosis / Q000378:metabolism / Q000473:pathology*; D002118:Calcium / Q000378:metabolism; D002417:Cattle; D006350:Heart Valve Prosthesis; D019918:Heart Valve Prosthesis Implantation / Q000295:instrumentation / Q000379:methods*; D007601:Jugular Veins / Q000378:metabolism / Q000473:pathology / Q000637:transplantation; D019060:Minimally Invasive Surgical Procedures / Q000379:methods; D023421:Models, Animal; D009206:Myocardium; D012756:Sheep; D015607:Stents
chemical_list: D002118:Calcium