Infective Endocarditis

Endovascular infection of cardiovascular structures, usually involving the cardiac valves

Aetiology

  • Usually the consequence of two factors: the presence of organisms in the bloodstream, and abnormal cardiac endothelium that facilitates their adherence and growth

Risk factors

  • Abnormal cardiac endothelium:
    • Previous rheumatic heart disease
    • Congenital heart disease
    • Age related valvular degeneration
    • Prosthetic heart valve
    • IV drug abuse
  • Organisms in the bloodstream:
    • PWID
    • ICED
    • Intravascular lines
    • Septicaemia

Causative organisms

  • Staphylococcus aureus is the most common cause → Tricuspid Valve
  • Streptococcus viridans → Mitral Valve
  • Stapylococcus epidermidis commonly causes IE in patients with prosthetic valves
    • Infection can be early (at time of valve insertion) or late (up to many years after valve insertion, due to co-incidental bacteraemia, many causative organisms)
  • Candida and Staph. aureus common in PWID
    • Right sided valves usually affected, especially tricuspid
  • Atypicals:
    • Coxiella burneti - farming, aortic valve, lifelong antibiotic therapy may be required
    • HACEK bacteria - associated with poor dental hygiene
    • Brucella - goats
    • Fungi - immune-compromised, PWID, IV lines

Clinical presentation

Acute

  • Overwhelming sepsis and failure
  • Usually due to aggressive organisms e.g. Staph. aureus

Subacute

Symptoms
  • Fever
  • Malaise
  • Weight loss
  • Tiredness
  • Dyspnoea
Signs
  • New/changing heart murmur
  • Finger clubbing
  • Splinter haemorrhages
  • Splenomegaly
  • Roth spots - non-specific red spots seen on the retina
  • Janeway lesions - non-tender, small, erythematous or haemorrhagic or nodular lesions on the palm or sole caused by septic emboli
  • Osler nodes - painful, red, raised lesions found on the palms or sole caused by immune complex deposition
  • Microscopic haematuria

Investigations

  • Blood culture - 3 sets taken
  • Echocardiogram - vegetations
  • Serology - consider if blood cultures negative to look for ‘atypical’ organisms

Management

Empirical treatment

  • Native valve IE severe sepsis (acute)
    • Fucloxacillin IV 12gr/day in 4-6 divided dosage
    • Gentamicin IV 3mg/kg/day
  • Native valve IE subacute
    • Ampicillin IV 12gr/day in 4-6 divided dosage + Ceftriaxone 4gr/day in 2 divided dosage
  • Prosthetic valve IE - vancomycin and gentamicin IV, add rifampicin PO on days 3-5
  • Suspected MRSA - vancomycin and gentamicin IV, add rifampicin PO on days 3-5
  • PWID - flucloxacillin IV

Culture-specific treatment

  • Staphylococcus aureus (not MRSA)
    • Fucloxacillin IV 12gr/day in 4-6 divided dosage
    • Cephazoline IV 6gr/day in 3 divided dosage
  • Staphylococcus viridans
    • Penicillin G IV 12-18 MU/day in 4-6 divided dosage
    • Amoxicillin 100-200mg/kg/day in 4-6 divided dosage
    • Ceftriaxone 2gr/day
  • Staphylococcus epidermidis - vancomycin and gentamicin IV, add rifampicin PO on days 3-5
  • MRSA - vancomycin and gentamicin IV, add rifampicin PO on days 3-5
  • Enterococcus sp. - amoxicillin/vancomycin and gentamicin IV

Prophylaxis

  • Antibiotic prophylaxis not routinely recommended but can be indicated in some cases e.g. patients with a prosthetic valve before dental treatment