[Morphology of infectious endocarditis affecting bioprostheses of the cardiac valves]

Four varieties of infectious endocarditis were identified after cardiac valve bioprostheses: early acute, early subacute, late acute, and late subacute forms. Any of these forms may be of bacterial, fungal, or mixed (bacterial and fungal) origin. In the early forms, the infection was of exogenous origin, with a predominance of Gram-positive organisms, whereas in the late forms it was endogenous with a preponderance of Gram-negative flora. The hallmarks of fungal thromboendocarditis were an early massive thrombosis of the bioprosthesis, multiple thromboembolism, and an absence of cellular reaction in the cuspal tissue. In the subacute bacterial endocarditis, progressive dysfunction of the bioprosthesis resulting from calcination of bacteria-containing cusps and thrombi was noted.