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For further information, see CMDT Part 33-09: Infective Endocarditis

Key Features

Essentials of Diagnosis

  • Preexisting organic heart lesion

  • Fever

  • Evidence of systemic emboli

  • Positive blood culture

  • Evidence of vegetation on echocardiography

General Considerations

  • Important factors that determine the clinical presentation

    • Nature of the infecting organism

    • Valve that is infected

    • Route of infection

  • Acute presentation

    • Caused by more virulent organisms, particularly Staphylococcus aureus

    • Rapidly progressive and destructive infection

    • Acute febrile illness

    • Early embolization

    • Acute valvular regurgitation

    • Myocardial abscess

  • Subacute presentation

    • Caused by viridans strains of streptococci, enterococci, and other gram-positive and gram-negative bacilli, yeasts, and fungi

    • Systemic and peripheral manifestations may predominate

  • Patients may have underlying cardiac disease, but its prevalence as a risk factor is decreasing

  • The initiating event is colonization of the valve by bacteria during a transient or persistent bacteremia

Native valve endocarditis

  • Most commonly due to

    • S aureus

    • Viridans streptococci

    • Enterococci

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

  • Injection drug users

    • S aureus in at least 60% of cases and 80–90% of tricuspid valve infections

    • Enterococci and streptococci comprise the balance in about equal proportions

    • Other causes

      • Gram-negative aerobic bacilli

      • Fungi

      • Unusual organisms

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 and fungi

  • Late prosthetic valve endocarditis

    • Resembles native valve endocarditis

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


  • Endocarditis occurs in individuals with

    • Injection drug use

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

    • Prosthetic valve replacement

Clinical Findings

Symptoms and Signs

  • Most present with a febrile illness that has lasted several days to 2 weeks

  • Heart murmurs

    • In most cases, preexisting heart murmurs are stable

    • A new or changing murmur is significant diagnostically, but it is the exception rather than the rule

  • Characteristic peripheral lesions occur in up to 20–25% of patients

    • Petechiae (on the palate or conjunctiva or beneath the fingernails)

    • Subungual ("splinter") hemorrhages

    • Osler nodes (painful, violaceous raised lesions of the fingers, toes, or feet)

    • Janeway lesions (painless erythematous lesions of the palms or soles)

    • Roth spots (exudative lesions in the retina)

Differential Diagnosis

  • Valvular abnormality without endocarditis

    • Rheumatic heart disease

    • Mitral valve prolapse

    • Bicuspid or calcific aortic valve

  • Flow murmur (anemia, pregnancy, hyperthyroidism, sepsis)

  • Atrial myxoma

  • Noninfective endocarditis, eg, systemic lupus erythematosus (Libman-Saks endocarditis), marantic endocarditis (nonbacterial thrombotic endocarditis)

  • Hematuria due to other causes, such as

    • Glomerulonephritis

    • Renal cell carcinoma

  • Acute rheumatic fever

  • Vasculitis


Laboratory Tests

  • Blood culture

    • Three sets of blood cultures before starting antibiotics ...

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