7.1. Infective Endocarditis

📄 Definition

Infective endocarditis (IE) is an infection of the endocardial surface of the heart, typically involving the heart valves. It is a life-threatening condition requiring prompt diagnosis and treatment.

🧪 Causative Organisms – Mnemonic: SHAVE

  • Staphylococcus aureus – most common overall (especially in IVDU)

  • HACEK organisms – Gram-negative (Haemophilus, Aggregatibacter, Cardiobacterium, Eikenella, Kingella)

  • Alpha-haemolytic Streptococci (Viridans group) – dental link

  • Valvular prostheses – ↑ risk of coagulase-negative staph (e.g. S. epidermidis)

  • Enterococci – linked with GI or GU procedures

⚠️ Risk Factors

  • Prosthetic heart valves

  • Intravenous drug use (IVDU)

  • Structural heart disease (e.g. bicuspid aortic valve, mitral valve prolapse)

  • Previous IE

  • Indwelling catheters or invasive procedures (dental/GI)

📋 Clinical Features – Mnemonic: FROM JANE

  • Fever (most common)

  • Roth spots (retinal haemorrhages with pale centre)

  • Osler nodes (painful fingertip nodules – immune complex)

  • Murmur (new or changing)

  • Janeway lesions (painless palm/sole macules – septic emboli)

  • Anaemia of chronic disease

  • Nail-bed (splinter) haemorrhages

  • Emboli – e.g. stroke, PE, renal infarcts

🧠 Diagnosis – Modified Duke Criteria

🔹 Major Criteria:

  • Positive blood cultures (e.g. typical organisms in 2 separate samples)

  • Endocardial involvement on echocardiogram (vegetation, abscess, new regurgitation)

🔸 Minor Criteria:

  • Predisposing heart condition or IVDU

  • Fever ≥38°C

  • Vascular phenomena (Janeway, emboli)

  • Immunologic phenomena (Osler, Roth, GN, RF+)

  • Positive cultures not meeting major criteria

✅ Diagnosis: 2 major, or 1 major + 3 minor, or 5 minor

🔬 Investigations – Tiered Approach

🥇 First-Line:

  • 3 sets of blood cultures (at least 1 hour apart, different sites)

  • FBC, U&Es, LFTs, CRP/ESR

  • ECG – baseline for comparison

  • Transthoracic Echo (TTE)

🥈 Second-Line:

  • Transoesophageal Echo (TOE) – more sensitive

  • Urinalysis – haematuria (immune complex GN)

  • CXR – pulmonary emboli or signs of heart failure

🥉 Special Tests:

  • Serology – Coxiella, Bartonella (culture-negative IE)

  • Rheumatoid factor

  • Autoantibodies (ANA, ANCA)

Management – Mnemonic: BITE

  • Blood cultures (before antibiotics)

  • Initiate empiric IV antibiotics (e.g. amoxicillin + gentamicin)
    → adjust per microbiology

  • TOE to confirm vegetations

  • Escalate to cardiology/cardiothoracics if:

    • Persistent infection

    • Severe valve dysfunction/heart failure

    • Embolic risk

    • Prosthetic valve involvement

🔒 NICE NG183 advises 4–6 weeks IV antibiotics based on microbiology.

❗ Complications – Mnemonic: HEART

  • Heart failure (valve destruction)

  • Embolic events (stroke, spleen, kidney, lung)

  • Abscesses (myocardial, perivalvular)

  • Renal damage (GN, infarcts)

  • Total valve destruction → surgery

🦷 Prevention

  • Good dental hygiene

  • Antibiotic prophylaxis only in high-risk patients undergoing invasive dental procedures:

    • Prosthetic valves

    • Previous IE

    • Congenital heart disease (unrepaired or repaired with prosthesis)

🔺 Last updated in line with NICE NG183 – Endocarditis (antimicrobial prescribing)
Published: November 2020 • Last updated: January 2023
Last reviewed: August 2025
✅ PASSMAP ensures all content is NICE-aligned and reviewed for Physician Associate Registration Assessment (PARA) success.

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