Infective Endocarditis

Severe and life-threatening infection of cardiac skeletal structures, characterised by:

Epidemiology and Risk Factors

Risk factors:

  • Cardiac
    • Abnormal valve
      More likely to become infected, and more difficult to eradicate infection from.
      • Rheumatic
      • Degenerative
    • Intracardiac device
      • Prosthetic valve
      • Implantable wires
  • Bacteraemia
    • Concurrent infection
    • IVDU

Pathophysiology

Aetiology

Bacterial infection predominates, common causative organisms include:

  • Gram positive cocci
    • Staphylococci
    • Streptococci
      • S. Mitis and S. viridans endocarditis and bacteraemia are associated with colonic polyps and may precede colon cancer
    • Enterococci
  • Gram negatives
    • Coxiella burnetii Q fever, culture negative.
    • HACEK organisms
      Usually culture negative.
      • Haemophilus spp.
      • Actinobacillus
      • Cardiobacterium hominis
      • Eikenella corrodens
      • Kingella kingae

Fungal endocarditis is rare, and seen with:

  • Immunocompromise
  • IVDU

Clinical Features

Assessment

History:

Exam:

  • Skin findings
    • Osler’s nodes
    • Janeway lesions
    • Splinter haemorrhages
    • Roth spots
  • Embolism
    • Neurological
    • Renal

Investigations

Bedside:

  • Echocardiography
    • Modality
      • TTE
      • TOE
        Better imaging of valvular structures and device leads.
    • Features
      • Vegetation
      • Valvular destruction
        • Regurgitation
        • Dehiscence of prosthetic valve
      • Fistula
      • Ventricular dysfunction

Laboratory:

  • Bloods
    • FBE
    • UEC
    • Blood cultures

Imaging:

  • CT
    • Embolic phenomena
  • MRI
    • Embolic phenomena
      Particularly strokes.

Other:

  • Colonoscopy
    If S. mitis or S. viridans as the causative organism.

Diagnostic Approach and DDx

Duke Criteria for Infective Endocarditis
Major Minor

Typical microorganisms in blood cultures

  • 2 separate cultures
  • 2 cultures 12 hours apart
  • 3/4 cultures taken within 1 hour

Echocardiographic evidence of:

  • Abscess
  • Vegetation
  • Prosthetic valve dehissence
  • Predisposing condition
    • Mechanical valve
    • IVDU
  • Fever >38.0°
  • Vascular manifestations
    e.g. Janeway lesion.
  • Immunologic manifestation
    e.g. GN.
  • Positive blood cultures
    Not meeting major criteria.
  • Echocardiographic findings
    Not meeting major criteria.

Diagnosis requires one of:

  • Both major and one minor criteria
  • One major and three minor criteria
  • Five minor criteria

The Duke criteria are broadly accepted, but somewhat limited as 20% of endocarditis is culture negative.

Management

Specific therapy:

  • Pharmacological
    • Early antimicrobial therapy
      • Extended duration
        Classically 6 weeks.
      • Local-microbiome adjusted
        Consider:
        • Flucloxacillin
        • Vancomycin
        • Benzylpenicillin
        • Gentamicin
  • Procedural
    • Surgery is the cornerstone of curative therapy
    • The decision on when to operate is complex and driven by the balance of:
      • Delaying for pre-operative optimisation
      • Intervening to prevent further decline
    • The decision should be multidisciplinary, but factors favouring proceeding include:
      • Cardiac failure
        • Refractory shock/pulmonary oedema infers urgent surgery
      • Uncontrolled infection
        Persistent positive blood cultures despite 3-10 (recommendations vary) days of appropriate antibiotic treatment.
      • Embolisation
        • Large (>1cm) vegetation at risk of embolising
        • Ongoing embolic phenomena
          Decision confounded by intracranial haemorrhage, which has substantial implications for therapeutic heparin required for CPB.
      • Aortic root abscess

Supportive care:

Disposition:

  • ICU admission common for:
    • Heart failure
    • Septic shock
    • Neurological involvement

Marginal and Ineffective Therapies

Anaesthetic Considerations

Complications

  • C
    • Embolism
      • Pulmonary
        For right sided disease.
      • Stroke
        15-30%.
      • Splenic
      • Renal
  • I
    • Sepsis

Prognosis

Varies depending on the extent of valvular disease and severity of systemic infection, however:

  • Mortality
    • 30-50% in patients receiving surgical treatment
    • 85% in those not receiving operative intervention

Key Studies

References

  1. Bersten, A. D., & Handy, J. M. (2018). Oh’s Intensive Care Manual. Elsevier Gezondheidszorg.
  2. Sharma A, Masood U, Kahlon A, Pattar S, Iqbal S, Lehmann D. Streptococcus Mitis Bacteremia and Endocarditis: An Early Sign in Pre-Cancerous Colon Polyps: 1366. Official journal of the American College of Gastroenterology | ACG. 2016;111:S616.