Infective endocarditis in children

Overview

Infective endocarditis (IE) is infection of the endocardial surface of the heart, mostly the valves, by bacteria or, less often, fungi. In children it almost always occurs on an abnormal heart: congenital lesions, rheumatic valves, surgical patches, shunts, prosthetic valves or around central venous catheters.

It is easy to miss: fever with a murmur may be put down to a simple infection. Untreated, IE is almost always fatal, so think of it in any child with heart disease and unexplained fever.

Pathophysiology and risk factors

How a vegetation forms

1. A high-velocity jet or turbulent flow (for example through a VSD, a narrow valve, a PDA) damages the endothelium.
2. Platelets and fibrin stick to the damaged area, forming a sterile clot (non-bacterial thrombotic endocarditis).
3. A transient bacteraemia (often from the mouth) seeds the clot.
4. Bacteria multiply, protected inside layers of fibrin and platelets: the vegetation.
5. Pieces break off as emboli; immune complexes cause vasculitic and renal signs.

Lesions at risk

Isolated secundum ASD does not need endocarditis prophylaxis (Akbar).

Organisms

Clinical presentation

Symptoms

• Prolonged fever (often low grade), chills, night sweats.
• Fatigue, malaise, weight loss.
• Joint and muscle pains, headache, chest pain, breathlessness.

Signs

Investigations

Blood cultures (the key test)

• Take at least three separate blood cultures within 24 hours, from different venepunctures, before starting antibiotics (Akbar).
• The aim is to show continuous bacteraemia. Three separate venepunctures give near-maximal yield (about 95%) in a child not recently given antibiotics; a child recently or currently on antibiotics needs extra serial cultures (Nelson).
• Culture-negative IE: no organism is found in 10-15% of cases despite good technique (Nelson).

Echocardiography

• Transthoracic echo shows vegetations (from about 2 mm), valve regurgitation, abscess and dehiscence of prosthetic material.
• Transoesophageal echo is more sensitive in adolescents, adults and anyone with a prosthetic valve; in most children it is not needed (Nelson).

Other tests

Modified Duke criteria

Major criteria

1. Positive blood cultures: a typical organism in two or more separate cultures; or positive cultures taken over 12 hours apart, or four positive cultures at any timing; or Coxiella burnetii (Nelson).
2. Evidence of endocardial involvement on echo: vegetation, paravalvular abscess or new dehiscence of a prosthetic valve.
3. New valvular regurgitation (a new murmur heard clinically).

Minor criteria

1. Predisposition: predisposing heart condition (including previous IE) or injection drug use.
2. Fever of 38 °C (100.4 °F) or more.
3. Vascular phenomena: major arterial emboli, septic pulmonary infarcts, mycotic aneurysm, intracranial haemorrhage, conjunctival haemorrhage, Janeway lesions.
4. Immunological phenomena: glomerulonephritis, Osler nodes, Roth spots, positive rheumatoid factor.
5. Microbiological evidence: a positive blood culture not meeting the major criterion, or serological evidence of active infection with a likely organism.

Diagnosis

Management

Medical: principles

• Bactericidal, intravenous antibiotics in high doses.
• Long course: 4-6 weeks (Akbar; Nelson gives 4-8 weeks), because the drug must reach organisms by slow diffusion through the fibrin mesh. Nelson notes that susceptible viridans streptococci can be treated with penicillin G alone for 4 weeks.
• Choose by organism and sensitivity; start empirically after cultures if the child is unwell.
• Monitor fever, repeat cultures and gentamicin levels (aminoglycoside dosing is guided by serum levels, Nelson); watch for complications by examination and echo.

Regimens (doses from Akbar)

Surgical management

Akbar: surgery may be needed to remove vegetations or replace a valve. Nelson lists the indications:

• Medical treatment failing, with persistent bacteraemia.
• An unusual or hard-to-treat organism, such as fungal endocarditis.
• Valve ring (annulus) or myocardial abscess.
• Rupture of a valve leaflet.
• Valve regurgitation with acute or refractory heart failure.
• Recurrent serious emboli.
• Refractory prosthetic valve disease.

Complications

• Congestive cardiac failure from valve damage (regurgitation, leaflet defects).
• Myocardial and valve ring abscess.
• Systemic emboli: stroke-like illness from cerebral abscess or aneurysm; kidney infarction; splenic abscess, which can bleed fatally.
• Pulmonary emboli.
• Mycotic aneurysm.
• Glomerulonephritis (immune complex).
• Metastatic infection: arthritis, meningitis, pericarditis, abscesses.

Outcome (Nelson): cure over 90% for viridans streptococci on a native valve, 75-90% for enterococcus, 60-75% for acute S. aureus disease, and about 50% for fungal endocarditis.

Prevention

Good dental and skin care

• Regular dental care and good oral hygiene in every child with heart disease, since oral bacteria are the usual source.
• Care of central lines, which are the main link with neonatal endocarditis.

Antibiotic prophylaxis

• Akbar: give an antibiotic before and during procedures that cause bacteraemia in susceptible children: oral amoxicillin for dental or respiratory procedures; oral amoxicillin, or parenteral ampicillin plus gentamicin, for GI or genitourinary manipulation; clindamycin for penicillin allergy.
• Nelson's approach: prophylaxis is for high-risk children (prosthetic valves or material, previous IE, unrepaired cyanotic disease, within 6 months of repair with prosthetic material, residual defects near prosthetic material, transplant valve disease) before dental procedures that manipulate the gums or the periapical region, and invasive procedures on the respiratory tract, infected skin or muscle.
• Nelson's regimen: oral amoxicillin 50 mg/kg (maximum 2 g) 30-60 minutes before the procedure; clindamycin or azithromycin if allergic to beta-lactams. Prolonged or continuous prophylaxis is not recommended.

Quick revision

• IE = infection of endocardium/valve on an abnormal heart; untreated, nearly always fatal.
• Viridans strep about 50% (mouth); staph about 30% (lines, surgery).
• Signs: fever, new or changing murmur, splenomegaly, petechiae, splinter haemorrhages, clubbing, Osler, Janeway, Roth.
• At least 3 blood cultures within 24 h before antibiotics; echo for vegetation.
• Duke: 2 major, or 1 major + 3 minor, or 5 minor.
• IV antibiotics 4-6 weeks; surgery for failure, abscess, uncontrolled infection, emboli, fungi.
• Prevent: dental hygiene; amoxicillin before dental procedures in high-risk children.

Written by The House Job from standard references (Basis of Paediatrics by Pervez Akbar; Nelson Essentials of Paediatrics).

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