Infective endocarditis
- Lesion
Germs settle on a heart valve and form a friable clump that destroys the valve and throws infected fragments into the blood.
What it is
Infective endocarditis is a microbial infection of the heart valves or endocardium that forms vegetations of thrombus, organisms and inflammatory cells. Acute endocarditis is caused by highly virulent organisms, most commonly Staphylococcus aureus, which can attack normal valves and destroy them within days. Subacute endocarditis is caused by less virulent organisms such as viridans streptococci, usually on previously abnormal valves, over weeks to months. Prosthetic valves, intravenous drug use, catheters and dental or other procedures are important risks.
Structure
- Gross: friable, bulky, destructive vegetations on the valve surface, usually on the side facing the flow (atrial side of AV valves, ventricular side of semilunar valves).
- Microscopy: fibrin and platelets with colonies of bacteria and neutrophils; subacute lesions show granulation tissue and fibrosis at the base.
Acute versus subacute infective endocarditis
| Form | Organisms and valves | Course and pathology |
|---|---|---|
| Acute | Staphylococcus aureus (also pneumococcus, gonococcus); normal or abnormal valves; tricuspid in drug users | Days; large destructive vegetations, perforation, ring abscess, metastatic abscesses |
| Subacute | Viridans streptococci, enterococci, HACEK; previously damaged valves | Weeks to months; smaller vegetations, granulation tissue at the base, immune phenomena |
Clinical notes
- Diagnosis rests on blood cultures and echocardiography (modified Duke criteria).
- Fever plus a new murmur, or embolic events in a patient with a risk factor, should raise the suspicion.
Test yourself
Think of the answer, then tap the question to see it.
Which organism causes most cases of acute infective endocarditis?
Staphylococcus aureus.
Which valve is typically affected in intravenous drug users?
The tricuspid valve.
Why should Streptococcus gallolyticus endocarditis prompt a colonoscopy?
Because it is strongly associated with colonic neoplasia.
Which two immune-mediated findings are typical of subacute endocarditis?
Immune-complex glomerulonephritis and Osler nodes (also Roth spots).
Elsewhere in DurgiPedia
Connections
Educational content on the mechanisms of disease; not a diagnostic or treatment guide and no substitute for a health professional's advice. No doses are given.
Sources: Infective Endocarditis (StatPearls (NCBI Bookshelf), 2025); Endocarditis: MedlinePlus Medical Encyclopedia (MedlinePlus, US National Library of Medicine, 2025).
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Representative model, for educational purposes only.