title: Quantitative histological examination of bioprosthetic heart valves.
abstract: BACKGROUND
  The histological features that characterize infective endocarditis in bioprosthetic valves are not accurately defined. Moreover, bioprosthetic valves may have a noninfective, degenerative evolution associated with calcifications, vegetation-like lesions, and inflammatory infiltrates. Such histological findings may be misdiagnosed as infective endocarditis.
  
  
  METHODS
  Pathologic analysis of inflamed bioprosthetic valve tissues was conducted retrospectively for 21 patients who underwent surgical removal of a bioprosthetic valve because of suspected infective endocarditis and for 67 patients who underwent surgical removal of a bioprosthetic valve because of noninfective dysfunction. To better define the histological criteria for infective endocarditis, we used quantitative image analysis to compare these 2 groups of patients with respect to vegetations, calcifications, and patterns of inflammation.
  
  
  RESULTS
  Histologically, infective endocarditis in patients with bioprostheses was characterized by demonstration of microorganisms, vegetations, and neutrophil-rich, inflammatory infiltrates. Valve tissue specimens from patients whose bioprosthetic valves were removed because of noninfective complications showed, in 30% of cases, inflammatory infiltrates mainly composed of macrophages and lymphocytes. Inflammatory adherent thrombi that can occur to the surface of noninfective degenerative bioprostheses are differentiated because their vegetations have macrophage-rich content. A neutrophil surface area with a cutoff value of > or =1.5% of the total valve tissue surface area is highly specific (94%) for infective endocarditis.
  
  
  CONCLUSIONS
  When no microorganisms are detected and vegetations are not found in bioprosthetic valve tissues during the histological examination, a neutrophil-rich inflammation might better define the term "active endocarditis" in the Duke criteria and would allow differentiation between infective endocarditis and inflammatory, noninfective valve processes in patients with bioprosthetic valves.
authors.affiliation: Unité des Rickettsies et des Pathogènes Emergents, Faculté de Médecine, Université de la Méditerranée, Marseille, France.
authors.forename: Hubert
authors.initials: H
authors.lastname: Lepidi
authors.forename: Jean-Paul
authors.initials: JP
authors.lastname: Casalta
authors.forename: Pierre-Edouard
authors.initials: PE
authors.lastname: Fournier
authors.forename: Gilbert
authors.initials: G
authors.lastname: Habib
authors.forename: Frédéric
authors.initials: F
authors.lastname: Collart
authors.forename: Didier
authors.initials: D
authors.lastname: Raoult
mesh_terms: D000328:Adult; D000368:Aged; D001705:Bioprosthesis / Q000009:adverse effects*; D004697:Endocarditis, Bacterial / Q000209:etiology*; D005260:Female; D006350:Heart Valve Prosthesis / Q000009:adverse effects*; D006801:Humans; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies