Endocarditis, Infective

Key Features

Essentials of Diagnosis

• Fever

• Preexisting organic heart lesion

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

  • Systemic and peripheral manifestations may predominate

• Predisposing valvular abnormalities include

  • Many congenital disorders such as

    • Ventricular septal defect

    • Tetralogy of Fallot

    • Coarctation of the aorta

    • Patent ductus arteriosus

  • 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 and 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

  • 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 ...