Infective Endocarditis (IE)

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Infective Endocarditis (IE)   

1️⃣ Definition

  • Microbial infection of the endocardial surface (usually valves, but also septal defects, mural endocardium, CIED leads).

  • Characterized by vegetations (platelets + fibrin + microorganisms + inflammatory cells).


  • Clinical spectrum: acute (rapid, destructive) vs. subacute (indolent, chronic).

2️⃣ Etiology


By organism

  • Acute IE

    • Staphylococcus aureus (IVDU, healthcare-associated, prosthetic valves).

    • Highly virulent, infects normal valves.

  • Subacute IE

    • Viridans streptococci (oral flora → after dental procedures).

    • Enterococcus faecalis (GU/GI instrumentation).

    • Strep gallolyticus (bovis) → strong association with colorectal cancer.

  • Prosthetic valve IE (PVE)

    • Early (<60 days): Staph epidermidis, S. aureus, Gram-negative rods, fungi.

    • Late (>60 days): similar to native valve IE (viridans, enterococci, HACEK).

  • IV drug users

    • MC: S. aureus (often tricuspid valve).

    • Others: Pseudomonas, Candida.

  • Culture-negative IE (~10%)

    • HACEK (Haemophilus, Aggregatibacter, Cardiobacterium, Eikenella, Kingella).

    • Fastidious/atypical: Coxiella burnetii, Bartonella, Brucella, Chlamydia, Tropheryma whipplei.

3️⃣ Risk Factors

  • Structural heart disease: congenital (VSD, bicuspid AV), rheumatic, degenerative valves.

  • Prosthetic valves, CIEDs (pacemakers/ICDs).

  • IV drug use, indwelling catheters, hemodialysis.

  • Immunosuppression, diabetes, poor dentition.

4️⃣ Pathogenesis

  1. Endothelial damage → platelet-fibrin deposition (nonbacterial thrombotic endocarditis).

  2. Transient bacteremia (dental, GI, GU, skin breaks).

  3. Adhesion & invasion by organisms → vegetations.

  4. Consequences:

    • Valve destruction → regurgitation/stenosis → heart failure.

    • Embolization → infarcts/abscesses.

    • Immune complex deposition → glomerulonephritis, Osler nodes, Roth spots.

5️⃣ Clinical Features

Constitutional

  • Fever (most common), night sweats, malaise, anorexia, weight loss.

Cardiac

  • New or changing murmur (85%).

  • Heart failure (leading cause of death).

  • Conduction abnormalities (AV block from abscess).

Peripheral Manifestations

  • Vascular phenomena (embolic):

    • Janeway lesions (nontender palms/soles).

    • Splinter hemorrhages.

    • Major arterial emboli (stroke, splenic infarct, renal infarct, septic PE).

  • Immunologic phenomena:

    • Osler nodes (tender finger/toe pads).

    • Roth spots (retinal hemorrhage with pale center).

    • GN (hematuria, proteinuria).

👉 Classic mnemonic: FROM JANE
Fever, Roth spots, Osler nodes, Murmur, Janeway lesions, Anemia, Nail hemorrhages, Emboli.

6️⃣ Diagnosis

Modified Duke–ISCVID 2023 Criteria

  • Definite IE: 2 major OR 1 major + 3 minor OR 5 minor.

  • Possible IE: 1 major + 1 minor OR 3 minor.

Major

  • Positive blood cultures (typical organisms, persistent, or single positive for Coxiella).

  • Echo/CT: vegetation, abscess, prosthetic dehiscence, new regurgitation.

Minor

  • Predisposing condition (IVDU, prosthetic valve, structural heart disease).

  • Fever ≥ 38°C.

  • Vascular phenomena.

  • Immunologic phenomena.

  • Positive blood culture not fulfilling major.

Investigations

  • Blood cultures: ≥3 sets, different sites, before antibiotics.

  • Echocardiography:

    • TTE (first-line).

    • TEE (better sensitivity, esp. prosthetic valves, S. aureus, inconclusive TTE).

  • Labs: ↑ ESR/CRP, normocytic anemia, microscopic hematuria, rheumatoid factor.

  • Imaging: CT/MRI for embolic complications, PET/CT (prosthetic valves).

  • Colonoscopy if Strep gallolyticus.

7️⃣ Management

Empiric Antibiotics (start after cultures)

  • Native valve, community-acquired: Vancomycin + ceftriaxone.

  • Prosthetic valve: Vancomycin + gentamicin + cefepime/ceftriaxone.

  • Duration: 4–6 weeks IV.

Targeted therapy (examples)

  • MSSA: nafcillin/oxacillin.

  • MRSA: vancomycin or daptomycin.

  • Viridans strep: penicillin G or ceftriaxone ± gentamicin.

  • Enterococcus: ampicillin + gentamicin OR ampicillin + ceftriaxone.

  • HACEK: ceftriaxone.

  • Fungal: amphotericin B or echinocandin ± valve surgery.

Surgery Indications

  • Heart failure due to valve dysfunction.

  • Uncontrolled infection: abscess, persistent bacteremia, fungal/MDRO.

  • Prevention of embolism: vegetation >10 mm with recurrent emboli.

8️⃣ Complications

  • Cardiac: CHF, abscess, fistula, conduction block, prosthetic dehiscence.

  • Embolic: stroke, splenic/renal infarcts, septic PE.

  • Infectious metastasis: brain abscess, vertebral osteomyelitis, mycotic aneurysm.

  • Renal: GN, infarction, drug nephrotoxicity.

9️⃣ Prognosis

  • Mortality: ~15–30%.

  • Worse prognosis with: prosthetic valves, S. aureus, fungi, elderly, heart failure, perivalvular abscess.

🔟 Prevention

  • Antibiotic prophylaxis (amoxicillin before dental/respiratory/infected skin procedures) only for:

    • Prosthetic valves.

    • Previous IE.

    • Certain congenital defects.

    • Heart transplant recipients with valvulopathy.

💡 Clinical Pearls

  • S. gallolyticus → always do colonoscopy (CRC risk).

  • IVDU → usually tricuspid valve → septic pulmonary emboli.

  • Acute severe MR or AR + fever → think IE.

  • TEE is superior to TTE (esp. prosthetic or obese patients).

  • Avoid anticoagulation unless another indication (risk of hemorrhagic stroke with emboli).

  • Persistent fever despite antibiotics? → suspect abscess or resistant bug.

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