Infective endocarditis is an infection on the endothelial surface of the heart, including the heart valves. The management of infections on the endothelial surfaces of blood vessels is very similar. Infectious endothelial lesions, called vegetations, usually occur on the valve leaflets and are composed of microorganisms trapped in a fibrin mesh that extends into the bloodstream.
Many microorganisms have been reported to cause endocarditis, although there are only a few principal causes in children (Table 111-1). Viridans streptococci are the principal causes in children with congenital heart diseases without previous surgery. Staphylococcus aureus and coagulase-negative staphylococci are important causes of endocarditis, especially following cardiac surgery and in the presence of prosthetic cardiac and endovascular materials.
Infective endocarditis among children is primarily a complication of congenital heart disease and cardiac surgery, although it can occur in a previously normal native valve. Patients at high risk for infective endocarditis include those with prosthetic cardiac valves or prior infective endocarditis; children who have unrepaired cyanotic congenital heart disease, are within 6 months of repair using prosthetic material, or have residual defects at or near a site of prosthetic material; or transplant patients who develop valvular lesions. The risk is increased after dental and oral procedures or instrumentation or surgical procedures of the respiratory tract, genitourinary tract, or gastrointestinal tract. Rheumatic heart disease is a risk factor but is uncommon. Neonatal endocarditis is associated with the use of central vascular catheters and surgery
Viridans streptococci (the most common causative organism at all ages)*
Hemolytic streptococci: groups A, B (in neonates and elderly), C, G, D
HACEK organisms (i.e., Haemophilus aphrophilus, Actinobacillus actinomycetemcomitans, Cardiobacterium hominis, Eikenella corrodens, and Kingella kingae)
Coxiella burnetii (Q fever) Chlamydia Agents of culture-negative endocarditis *Most common causes of infective endocarditis in children.
in neonates. Endocarditis is a sporadic disease with no geographic predisposition and little gender or socioeconomic predisposition in children.
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The most common early symptoms of infective endocarditis are nonspecific and include fever, malaise, and weight loss. Tachycardia and a new or changed heart murmur are common findings. The subtle and nonspecific findings underscore the need to obtain blood cultures if endocarditis is suspected, especially for children with congenital heart disease and for unexplained illness after dental or surgical procedures. Endocarditis is usually a subacute, slowly progressive process, but acute endocarditis is often due to S. aureus and may resemble sepsis. Heart failure, splenomegaly, petechiae, and embolic phenomena (Osler nodes, Roth spots, Janeway lesions, and splinter hemorrhages) may be present.
The key to diagnosis is confirming continuous bacteremia or fungemia by culturing the blood. Multiple blood cultures are performed before initiating antibiotic therapy. Three separate venipunctures for blood culture achieve near-maximal sensitivity (about 95%) among patients who have not been treated recently with antibiotics. Patients who have been treated with antibiotics recently or who are currently receiving antibiotics should have additional serial cultures performed. Despite adequate blood culture techniques, the microbiologic diagnosis is not confirmed in 10% to 15% of cases, known as culture-negative endocarditis.
Erythrocyte sedimentation rate and C-reactive protein are often elevated. Leukocytosis, anemia, and hematuria are common laboratory findings. A positive rheumatoid factor or antinuclear antibody may also be seen.