Infective Endocarditis (IE)
Description
Infective Endocarditis (IE) is an infection of the endocardial surface of the heart, including:
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Heart valves
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Mural endocardium
It is primarily caused by bacteria, hence also known as bacterial endocarditis.
Risk Factors
| Risk Factor Category | Examples |
|---|---|
| Congenital heart disease | Especially cyanotic congenital heart disease |
| Acquired structural disease | Rheumatic heart disease |
| Prosthetic material | Prosthetic heart valves |
| Previous infection | History of infective endocarditis |
| Vascular access risks | IV drug use, chronic IV access |
| Immunocompromised states | HIV infection, diabetes |
Classification
1. Acute Infective Endocarditis
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Caused by highly virulent organisms (e.g., Staphylococcus aureus, enterococci, streptococci)
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Can infect normal endocardium
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Abrupt onset with high-grade fever
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Causes destructive lesions:
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Ulceration
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Perforation
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Severe regurgitation
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Ring abscesses (especially around prosthetic valves)
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2. Subacute Infective Endocarditis
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Caused by less virulent organisms
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Streptococcus viridans
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HACEK group (Haemophilus, Aggregatibacter, Corynebacterium, Eikanella, Kingella)
-
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Insidious onset with:
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Low-grade fever
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Anorexia
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Weight loss
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Myalgia, influenza-like symptoms
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Pleuritic chest pain
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No specific acute pathological features
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Slowly progressive chronic inflammation with stable, tightly adherent vegetations
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Persistent antigenemia predisposes to immune complex formation
Investigations
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Full Blood Count with Differential (FBC/DC)
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ESR
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ECG and Echocardiography
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Chest X-ray
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Blood cultures: 3 samples within 24 hours
A fever with a new or changing murmur is IE until proven otherwise.
Duke’s Criteria for Diagnosis of Infective Endocarditis
| Major Criteria | Minor Criteria |
|---|---|
| Positive blood cultures: typical organisms from ≥2 cultures; persistently positive cultures; or positive for Coxiella burnetii | Predisposing heart condition or IV drug use |
| Microorganisms consistent with IE from ≥2 cultures drawn >12 h apart | Fever ≥ 38°C |
| All of 3, or majority of ≥4 blood cultures | Vascular phenomena (arterial emboli, septic pulmonary infarcts, mycotic aneurysm, intracranial haemorrhage, conjunctival haemorrhages, Janeway lesions) |
| Positive serology or high titre for Coxiella burnetii | Immunologic phenomena (glomerulonephritis, Osler nodes, Roth’s spots, rheumatoid factor) |
| Evidence of endocardial involvement: positive echo showing vegetation, abscess, prosthetic valve dehiscence, or new regurgitation | Microbiological evidence not meeting major criteria |
Diagnosis:
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2 major, OR
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1 major + 3 minor, OR
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5 minor criteria
Treatment
Table 49: Management of Infective Endocarditis
| Drugs | Dosage | Duration | Remarks |
|---|---|---|---|
| 1st Line | |||
| Crystalline Penicillin (X-Pen) | 50–100,000 IU/kg/day in 4 divided doses | 4 weeks | |
| AND Gentamicin | 3–5 mg/kg/day in 2–3 divided doses | 4 weeks | |
| THEN Ciprofloxacin | 15 mg/kg/day in 2 divided doses | 2 weeks | |
| Ceftriaxone | 80–100 mg/kg/day once or twice daily | 4 weeks | |
| AND Gentamicin | 3–5 mg/kg/day in 2–3 divided doses | 4 weeks | |
| THEN Ciprofloxacin | 15 mg/kg/day in 2 divided doses | 2 weeks | |
| 2nd Line | |||
| Vancomycin | 30–40 mg/kg/day in 4 divided doses | 4 weeks | |
| AND Gentamicin | 3–5 mg/kg/day in 2–3 divided doses | 4 weeks | |
| THEN Ciprofloxacin | 15 mg/kg/day in 2 divided doses | 2 weeks |