Pediatric Bacterial Endocarditis Workup

Under the modified Duke criteria, the clinical criteria for definite infectious endocarditis includes 2 major, 1 major and 3 minor, or 5 minor criteria, as follows ^[9] :

Major criteria

Major criteria include positive blood cultures, in this case two separate cultures for a typical endocarditis microorganism, such as Streptococcus viridans or a HACEK organism (Haemophilus parainfluenzae, H aphrophilus, H paraphrophilus, Actinobacillus actinomycetemcomitans, Cardiobacterium hominis, Eikenella corrodens, or Kingella species); persistently positive blood cultures; or evidence of infection with a Coxiella organism and/or Q fever.

Another criterion is the presence of positive echocardiographic findings (eg, oscillating mass and/or vegetation, paravalvular abscess, or dehiscence of a prosthetic valve).

A third criterion is new valvular regurgitation.

Minor criteria

Minor criteria include the following:

• Predisposing condition (history of IV drug use or congenital heart disease)

• Fever with a temperature of more than 38°C

• Vascular phenomena (arterial emboli, septic pulmonary infarcts, intracranial hemorrhage, conjunctival hemorrhage, Janeway lesions [painless, hemorrhagic lesions on the palms and soles])

• Immunologic phenomena (glomerulonephritis, Osler nodes, Roth spots, a positive result for rheumatoid factor)

• Positive blood culture findings without meeting the criteria above or serologic evidence of active infection consistent with endocarditis

• Definite infective endocarditis may be diagnosed if there is pathologic evidence of intracardiac or embolized vegetation or intracardiac abscess, or 2 major, or 1 major and 3 minor, or 5 minor clinical criteria are present

• Infective endocarditis is considered possible if 1 major and 1 minor or 3 minor criteria are present

• The diagnosis of infective endocarditis may be rejected if a firm alternate diagnosis is confirmed, if “infective endocarditis syndrome" resolves within 4 days of antibiotic therapy, if no pathologic evidence of infective endocarditis is found at surgery or autopsy within 4 days of antibiotic therapy, or if the case does not meet "possible infective endocarditis" criteria

Go to Infective Endocarditis for more complete information on this topic.

Blood culture

The most definitive laboratory tests for bacterial endocarditis are multiple blood cultures that grow an organism known to cause endocarditis.

Blood cultures should be obtained from all patients with fever of unclear etiology who have a pathologic heart murmur, a history of heart disease, or previous endocarditis.

For microbiologic documentation, obtaining 5-7 mL of blood from children (1-3 mL in infants) in 3 separate samplings within 1-24 hours is recommended, according to the clinical presentation.

The above recommendation is valid if the child is not ill. However, if the child is ill, three cultures may be obtained with 1 hour separating the first and last culture, before administering antibiotics.

Venous blood samples should be obtained from different peripheral sites.

It is not necessary to time blood sampling with fever because bacteremia in infective endocarditis is usually continuous.

The microbiology laboratory should be notified of the clinical suspicion for endocarditis. Cultures should be grown aerobically and anaerobically for at least 1 week.

If no growth is observed by the second day of incubation, 2 more blood cultures should be obtained.

Blood cultures should be repeated during therapy to demonstrate the clearance of bacteremia.

Blood culture is negative in 2.5 to 31% of cases of endocarditis. In such cases, real-time polymerase chain reaction (PCR) technique from whole blood samples may identify the offending organism with high degree of specificity and predictive values. ^[10]

Complete blood count

Anemia is present in 70-90% of patients and is usually normocytic and normochromic. Leukocytosis is noted in less than 50% of patients.

Erythrocyte sedimentation rate and C-reactive protein

The erythrocyte sedimentation rate (ESR) is elevated in almost all patients except those with CHF, renal failure, and disseminated intravascular coagulation (DIC). The mean ESR is 55 mm/h.

The C-reactive protein, although nonspecific, is elevated in most patients but decreases with successful treatment. Levels of C-reactive protein may be used to monitor response to antibiotic therapy.

Rheumatoid factor

A positive rheumatoid factor is observed in 40-50% of patients with endocarditis of more than 6 weeks' duration. Immune complexes are also observed in patients with prolonged disease.

Urinalysis

Urinalysis may reveal proteinuria (50-60%) and/or microscopic hematuria (30-50%).

Echocardiography

Echocardiography is the primary modality for detecting endocarditis in patients in whom the diagnosis is suspected. In fact, echocardiographic features suggestive of infectious endocarditis are considered major criteria for confirming the diagnosis. Typical findings include vegetations (see the image below), abscesses, and new valvular insufficiency.

Transthoracic echocardiography (TTE) has a greater sensitivity in infants and children than in adults. Its reported sensitivity is as high as 81%. It is the most common form of imaging used in children and is usually sufficient in most clinical circumstances. It should be remembered that very small vegetations are hard to detect because of the sensitivity of the echo signals.

Transesophageal echocardiography (TEE) is occasionally required when transthoracic acoustic windows are inadequate. This is most likely to occur in patients who are obese or very muscular, who have had cardiac surgery, or have pulmonary hyperinflation. TEE is especially useful in detecting aortic root abscess, involvement of the sinuses of Valsalva, and prosthetic valve dehiscence.

Magnetic resonance imaging

Magnetic resonance imaging (MRI) has identified paravalvular extension of infection, aortic root aneurysms, and fistulas. Its utility relative to echocardiography has not been widely established.