Write a Review
x
Feedback Cardiology

Infectious Endocarditis (IE)

  • Microbial infection of a heart valve, lining of a cardiac chamber, blood vessel or a congenital anomaly (septal defect)

Etiology

  • Bacteria
    • S.aureus (MCC of acute endocarditis) – originates from skin infections, abscesses, IVDUs
      • Highly virulent and invasive – produces florid vegetations and rapid valve destruction
    • S.epidermidis is a normal skin commensal – causes post op IE after cardiac surgery
    • Viridians strep (S.sanguis) are commensals in the upper respiratory tract – can enter blood stream during dental procedures
    • C.burnetti – in Q fever endocarditis
  • Yeast and fungi (rare) – Candida, Aspergillus
  • More likely to occur at sites of previous damage
  • Risk factors
    • Previous rheumatic heart disease
    • Age related valvular degeneration
    • Prosthetic valve
    • IVDU – MC site of infection is on the tricuspid valve and RHS of heart

Pathophysiology

  • Infection occurs at site of endothelial damage
    • They attract deposits of platelets and fibrin – increases vulnerability to colonisation by blood-borne organisms
    • Provides a protective environment for organisms to proliferate and evade host defence
  • Endocardial damage tends to occur around damaged valves
    • Aberrant jets of blood around the valves cause increased shearing forces in the endocardium
    • Valve cusps are avascular – so normal immune defences are impaired here
      • Further predisposes them to infection
  • When infection is established, vegetations form
    • Vegetations – when a thrombus is colonised by bacteria
    • Composed of organisms, fibrin, platelets
    • Can grow large enough to cause obstruction or embolism – in CNS, lungs, spleen, kidneys, liver
  • Adjacent tissues are destroyed and abscesses may form
  • Extra-cardiac manifestations – e.g. vasculitis or skin lesions
    • Due to emboli or immune complex deposition
  • Autopsy findings – spleen and kidney infarctions
Clinical feature

SABE (subacute bacterial endocarditis)

  • Suspected in pt with congenital or valvular heart disease who develop a persistent fever, malaise, night sweats, WL or new signs of HF
  • Purpura, petechial haemorrhages on skin and mucous membranes
  • Osler’s nodes – painful tender swellings at fingertips
  • Palpable spleen

ABE (acute endocarditis)

  • Presents as severe febrile illness with prominent murmurs and petechiae
  • Embolic events are common
  • Cardiac or renal failure
  • Abscesses

Post-op IE

  • Unexplained fever in pts after valve surgery – infection usually involves valve ring

Diagnosis

  • Duke’s criteria – see table
  • Blood culture
  • Echo – to detect vegetations, valve damage, abscesses
  • Elevated ESR + CRP
  • CXR – pulmonary oedema (rt side), pulmonary embolism (lt side)

Treatment

  • Remove source of infection
  • ABE – flucloxacillin [2g/6hrs] + gentamicin
  • SABE – benzyl pen [1.2g/4hrs] + gentamicin
  • Triple therapy for pts with pen allergy or MRSA infx
    • Vancomycin [2g/24hrs]
    • Gentamicin [80-120mg]
    • Rifampicin

Complications

If persistent fever

  • Perivalvular extension
  • Drug reactions
  • Nosocomial infection
  • Embolism
Feedback