INFECTIVE ENDOCARDITIS

An infection of the heart valves and lining of the heart chambers by microorganisms, usually bacterial, rarely fungal.

Causes

It is classified into 3 types:

  • Sub-acute endocarditis: caused by low virulence organisms such as Streptococcus viridans
  • Acute endocarditis: caused by common pyogenic organisms such as Staphylococcus aureus
  • Post-operative endocarditis: following cardiac surgery and prosthetic heart valve placement. The most common organism involved is Staphylococcus aureus

Clinical features

  • Disease may present as acute or chronic depending on the microorganism involved and patient’s condition
  • Fatigue, weight loss
  • Low grade fever and chills or acute severe septicaemia
  • Embolic phenomena affecting various body organs (e.g. brain)
  • Heart failure, prominent and changing heart murmurs
  • Splenomegaly, hepatomegaly
  • Anaemia
  • Splinter haemorrhages (nail bed and retina)
  • Finger clubbing
  • Diagnostic triad: persistent fever, emboli, changing murmur

Risk factors

  • Rheumatic heart disease, congenital heart disease
  • Prosthetic valve
  • Invasive dental/diagnostic/surgical procedures (including cardiac catheterization)
  • Immunosuppression
  • IV drug use/abuse

Note: Any unexplained fever in a patient with a heart valve problem should be regarded as endocarditis

Differential diagnosis

  • Cardiac failure with heart murmurs
  • Febrile conditions associated with anaemia

Investigations

  • Blood cultures: These are usually positive and all efforts should be made to identify the responsible pathogen and obtain sensitivity data
  • At least 3 sets of blood cultures (8 ml) each should be obtained (each from a separate venipucture) at least one hour apart
  • Blood: Complete blood count, ESR
  • Urinalysis for microscopic haematuria, proteinuria
  • Echocardiography
  • ECG

Management

  • Bed rest
  • Treat complications e.g. heart failure

Initial empirical antibiotic therapy

  • Benzylpenicillin 5 MU IV every 6 hours for 4 weeks
    Child: Benzylpenicillin 50,000 IU/kg every 6 hours for 4 weeks
  • Plus gentamicin 1 mg/kg IV every 8 hours for 2 weeks

If staphylococcus suspected, (acute onset) add:

  • Cloxacillin IV 3 g every 6 hours
    Child: 50 mg/kg every 6 hours for 4 weeks

If MRSA (Multi-Resistant Staphylococcus aureus)

  • Vancomycin 500 mg IV every 6 hours
  • Child: 10 mg/kg (infused over 1 hour) 6 hourly for 6 weeks

Once a pathogen has been identified

  • Amend treatment to correspond with the sensitivity results

Prevention

  • Prophylaxis in case of dental procedures and tonsillectomy in patients at risk (valvular defects, congenital heart disease, prosthetic valve). Give amoxicillin 2 g (50 mg/kg for children) as a single dose, 1 hour before the procedure.