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

Key Features

Essentials of Diagnosis

  • Fever

  • Preexisting organic heart lesion

  • Positive blood culture

  • 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, and other gram-positive and gram-negative bacilli, yeasts, and fungi

    • Systemic and peripheral manifestations may predominate

  • Predisposing valvular abnormalities include

    • Bicuspid aortic valves

    • Calcific or sclerotic aortic valves

    • Hypertrophic subaortic stenosis

    • Mitral valve prolapse

    • Variety of congenital disorders such as

      • Ventricular septal defect

      • Tetralogy of Fallot

      • Coarctation of the aorta

      • Patent ductus arteriosus

    • Rheumatic involvement of any valve

      • 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

  • 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 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 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

  • Culture-negative endocarditis may be due to

    • Bartonella species

    • Chlamydia species

    • Brucella species

    • Tropheryma whipplei

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

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

  • Symptoms also may occur as a result of

    • Embolization

    • Metastatic infection

    • Immunologically mediated phenomena, including

      • Cough

      • Dyspnea

      • Arthralgias or arthritis

      • Diarrhea

      • Abdominal, back, or flank pain

  • Characteristic peripheral lesions occur in about 25% of patients

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

    • Subungual ("splinter") hemorrhages

    • Osler nodes ...

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