nonbacterial thrombotic endocarditis

NBTE occurs when a hypercoagulable state or endothelial damage promotes deposition of platelets and fibrin on previously normal or damaged heart valves without microbial invasion. It is most commonly associated with advanced malignancy (particularly mucin-secreting adenocarcinomas of the pancreas, lung, colon, or ovary), which induces a procoagulant state via tissue factor release and tumor-associated mucin. It can also occur in the context of systemic lupus erythematosus (termed Libman-Sacks endocarditis, characteristically affecting the mitral and aortic valves with small verrucous vegetations on both surfaces of the leaflets), antiphospholipid antibody syndrome, sepsis, burns, and other severe systemic illnesses (hence the term 'marantic,' from Greek for 'wasting').

Pathologically, the vegetations are composed of fibrin and platelet aggregates without significant inflammatory or bacterial component, distinguishing NBTE from infective endocarditis (which shows destructive, bulky vegetations with organisms and inflammatory infiltrate) and from the verrucous lesions of rheumatic fever (which occur along lines of valve closure with associated inflammation).

Clinically, NBTE often presents with systemic embolization—stroke, splenic infarct, renal infarct, or limb ischemia—rather than symptoms directly referable to the heart, since the small vegetations rarely cause significant valve dysfunction. Blood cultures are negative, distinguishing NBTE from infective endocarditis, and echocardiography (particularly transesophageal) may reveal valvular vegetations without evidence of infection. Diagnosis often requires a high index of suspicion in patients with malignancy or lupus who develop embolic phenomena. Anticoagulation with heparin (rather than antiplatelet therapy) is often used to reduce embolic risk, though the underlying disease (e.g., cancer, lupus activity) should be treated. NBTE is a classic board topic tested in the context of hypercoagulability, paraneoplastic syndromes, and differentiating types of endocarditis (infective vs. nonbacterial vs. Libman-Sacks).