Noninfective endocarditis (thrombotic endocarditis, Libman-Sacks endocarditis)

1. Concept

Non-infective endocarditis = formation of sterile platelet/fibrin deposits on valves and adjacent endocardium — no microorganisms (in contrast to infective endocarditis). The two forms are non-bacterial thrombotic endocarditis (NBTE) and Libman-Sacks endocarditis (LSE).

2. Non-bacterial thrombotic endocarditis (NBTE)

• Sterile deposits of fibrin + blood elements along valve closure lines, forming in hypercoagulable states: sepsis, malignancy (esp. mucinous adenocarcinoma — marantic endocarditis), hyper-estrogenic states, endocardial trauma (catheters). Also seen with diabetes, cancer, chronic illness.
• Histology: bland thrombus without inflammation or valve damage (key distinguishing feature).
• Clinical: main danger is embolization (brain, heart, other organs); can be a nidus for subsequent infective endocarditis.

3. Libman-Sacks endocarditis (LSE)

• Sterile vegetations of SLE, classically on the mitral valve (on both surfaces of the leaflets).
• Composed of fibrinoid necrosis from immune-complex deposition; small, granular, pink.
• Often accompanied by valvulitis; healing → fibrosis and valve deformity.
• Now less common due to steroid treatment of SLE.

💡 High-yield: Non-infective endocarditis = sterile vegetations. NBTE (marantic) = bland fibrin thrombus, no inflammation, in hypercoagulable/malignancy states → embolization. Libman-Sacks = SLE, mitral valve, fibrinoid necrosis from immune complexes, vegetations on both leaflet surfaces.