title: Morphological findings in explanted Toronto stentless porcine valves.
abstract: BACKGROUND
  Stentless porcine valves have many documented advantages over stented valves. Since its introduction in 1991, the Toronto stentless porcine valve (T-SPV) has shown excellent hemodynamic performance.
  
  
  METHODS
  A total of 332 T-SPVs have been implanted at our institution up to December 2003, 25 of which have been explanted at surgery. Herein, we report a study of 30 explanted T-SPVs seen at our institution over a 5-year period.
  
  
  RESULTS
  The mean patient age at explant was 61.2+/-11.8 years with a mean implant duration of 100.7+/-27.8 months (after excluding one valve removed early postoperatively for infective endocarditis). Twenty-seven of 30 valves (90%) showed structural deterioration characterized by tissue degeneration, cusp tears, calcification, and lipid insudation. Eight valves (26.7%) showed evidence of calcification on gross inspection and a total of 23 valves (76.7%) showed at least one microscopic focus of calcification, located primarily in the basal and commissural regions of the cusp. Twenty valves (66.6%) showed cusp tears. Pannus was visible grossly on the surface of 27 of 30 valves (90%), while histologically, at least some degree of pannus was observed on both the inflow and outflow surfaces of all but two valves. Twelve T-SPV (40.0%) showed calcification in the porcine aortic tissue, four of which involved calcification of the porcine muscle shelf in the right coronary cusp. Two T-SPV showed no significant structural deterioration. Their clinical reason for explantation was incompetence or infective endocarditis.
  
  
  CONCLUSIONS
  With a freedom from reoperation of about 87.0% at up to 10 years, the T-SPV shows excellent durability. The majority of explanted valves show structural valve deterioration similar to that seen in other porcine heart valves.
authors.affiliation: Department of Pathology, E4-322, Toronto Medical Laboratories, Toronto General Hospital/University Health Network, Toronto, Ontario, Canada M5G 2C4. jagdish.butany@uhn.on.ca
authors.forename: Jagdish
authors.initials: J
authors.lastname: Butany
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Collins
authors.forename: Vidhya
authors.initials: V
authors.lastname: Nair
authors.forename: Richard L
authors.initials: RL
authors.lastname: Leask
authors.forename: Hugh E
authors.initials: HE
authors.lastname: Scully
authors.forename: William G
authors.initials: WG
authors.lastname: Williams
authors.forename: Tirone E
authors.initials: TE
authors.lastname: David
mesh_terms: D000818:Animals; D001705:Bioprosthesis; D002114:Calcinosis / Q000209:etiology; D004697:Endocarditis, Bacterial / Q000209:etiology; D004868:Equipment Failure; D005260:Female; D006350:Heart Valve Prosthesis; D019918:Heart Valve Prosthesis Implantation / Q000295:instrumentation*; D006801:Humans; D008297:Male; D008875:Middle Aged; D011183:Postoperative Complications / Q000473:pathology*; D013552:Swine