Pathology and pathogenesis of infective endocarditis in native heart valves.

Infective endocarditis is an endovascular microbial infection of cardiovascular structures, including large intrathoracic vessels and intracardiac foreign bodies. The characteristic lesions consist of vegetations composed of platelets, fibrin, microorganisms, and inflammatory cells, as well as leaflet disruption. The commonly accepted pathogenetic theory is herein reported, from endothelial injury with deposition of noninfective sterile thrombotic vegetations to transient bacteremia with microorganism adhesion (injury-thrombus-infection theory). This review addresses the pathology of native valve endocarditis, including local (valvular and perivalvular destruction) and distal (embolism, metastatic infection, and septicemia) complications. Old and new cardiac conditions and patients at risk, predisposing to the occurrence of infective endocarditis, are then discussed. Particular emphasis is given to hidden bicuspid aortic valve and the need of early carrier identification for prophylaxis.