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For further information, see CMDT Part 35-09: Infective Endocarditis

KEY FEATURES

Essentials of Diagnosis

  • Fever

  • Underlying valvular disease or prosthetic endovascular material

  • Positive blood cultures

  • Evidence of vegetation on echocardiography

  • Evidence of systemic emboli

General Considerations

  • Important factors that determine the clinical presentation

    • Infecting organism

    • Valve or valves that are infected

  • Acute presentation

    • Caused by more virulent organisms, particularly Staphylococcus aureus

    • Acute febrile illnesses

    • Early embolization

    • Acute valvular regurgitation

    • Myocardial abscess

  • Subacute presentation

    • Caused by viridans strains of streptococci, enterococci, other bacteria (including intracellular bacteria), yeasts, and fungi

    • Systemic and peripheral manifestations may predominate

  • Predisposing valvular abnormalities include

    • A variety of congenital heart disorders

    • Rheumatic involvement of any valve

    • Bicuspid aortic valves

    • Calcific or sclerotic aortic valves

    • Hypertrophic subaortic stenosis

    • Mitral valve prolapse

  • Rheumatic disease is no longer the major predisposing factor in developed countries

  • Regurgitation lesions are more susceptible than stenotic ones

Native valve endocarditis

  • Most commonly due to

    • S aureus

    • Viridans streptococci

    • Enterococci

    • HACEK organisms, an acronym for

      • Haemophilus aphrophilus (now Aggregatibacter aphrophilus)

      • Actinobacillus actinomycetemcomitans (now Aggregatibacter actinomycetemcomitans)

      • Cardiobacterium hominis

      • Eikenella corrodens

      • Kingella species

  • S aureus, and no longer streptococcal species, is now the leading cause

  • Gram-negative organisms and fungi account for a small percentage

  • In individuals who inject drugs

    • S aureus accounts for > 60% of cases and 80–90% of tricuspid valve infections

    • Enterococci and streptococci comprise most of the balance in about equal proportions

Prosthetic valve endocarditis

  • Early infections (within 2 months of valve implantation) are commonly caused by

    • Staphylococci—both coagulase-positive and coagulase-negative

    • Gram-negative organisms

    • Fungi

  • Late prosthetic valve endocarditis

    • Resembles native valve endocarditis

    • Most cases caused by streptococci, although coagulase-negative and coagulase-positive staphylococci cause a significant proportion of cases

Demographics

  • Endocarditis occurs in individuals with

    • Injection drug use

    • Underlying valvular disease (eg, congenital or rheumatic heart disease)

    • Prosthetic valve replacement

  • Culture-negative endocarditis may be due to

    • Organisms that require special media for growth (eg, Legionella, Bartonella, Abiotrophia species

    • Organisms that do not grow on artificial media (eg, Tropheryma whipplei, Coxiella burnetii, Chlamydia psittaci)

    • Organisms that may require prolonged incubation (eg, Brucella, anaerobes, HACEK organisms)

    • Bartonella quintana or Bartonella henselae are important causes of culture-negative endocarditis, most frequent among those with marginal housing status, that is typically diagnosed by serologies

CLINICAL FINDINGS

Symptoms and Signs

  • Fever

    • Presents in virtually all patients

    • However, may be low grade (< 38°C) in elderly individuals and in patients with heart failure or kidney failure

    • Rarely, there may be no fever at all

  • Duration of illness is a few days to a few weeks

  • Nonspecific symptoms are common

  • Initial symptoms and signs of endocarditis

    • May be caused by direct arterial, valvular, or cardiac damage

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