Quantitative histological examination of bioprosthetic heart valves.
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.
Lepidi
Hubert
H
Unité des Rickettsies et des Pathogènes Emergents, Faculté de Médecine, Université de la Méditerranée, Marseille, France.
Casalta
Jean-Paul
JP
Fournier
Pierre-Edouard
PE
Habib
Gilbert
G
Collart
Frédéric
F
Raoult
Didier
D
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