infective%20endocarditis%20(pediatric)
INFECTIVE ENDOCARDITIS (PEDIATRIC)
Infective endocarditis is an infection of the endocardial surface of the heart including infections of the large thoracic vessels and intracardiac foreign bodies characterized by the presence of vegetation which is a nidus for microorganism invasion.
Native valve endocarditis is an endovascular microbial infection of native heart valves that may be local including valvular and perivalvular destruction or distal due to detachment of septic vegetations with embolism, metastatic infection and septicemia.
Prosthetic valve endocarditis is an endovascular microbial infection of prosthetic heart valves and may be classified as an infection likely to have been acquired perioperatively and thus being nosocomial or likely to have been community-acquired.

Diagnosis

Characteristics of Infective Endocarditis

  • Often presents in an occult fashion & early diagnosis depends on a high index of clinical suspicion especially in patients with congenital heart disease, prosthetic valves or previous infective endocarditis
  • Established diagnosis of infective endocarditis is demonstrated by a positive blood culture & involvement of the endocardium detected during sepsis or systemic infection
    • Infective endocarditis may also be established if there is involvement of the endocardium detected during sepsis or systemic infection even if blood culture is negative

Evaluation

MODIFIED DUKE CLINICAL CRITERIA FOR DIAGNOSIS OF INFECTIVE ENDOCARDITIS

Definite Infective Endocarditis

Pathologic Criteria

  • Microorganisms demonstrated by culture or histologic exam of a vegetation, a vegetation that has embolized, or an intracardiac abscess; or
  • Pathological lesions: vegetation or intracardiac abscess are present & confirmed by histology showing active endocarditis

Clinical Criteria: Using specific definitions found below

  • 2 major criteria; or
  • 1 major criterion + 3 minor criteria; or
  • 5 minor criteria

Possible Infective Endocarditis

  • Findings consistent with infective endocarditis but lacks points to be considered as “definite” but not “rejected”

Rejected Infective Endocarditis

  • Firm alternate diagnosis for manifestations of endocarditis; or
  • Resolution of manifestations of endocarditis with antibiotic therapy for ≤4 days; or
  • No pathological evidence of infective endocarditis at surgery or autopsy, after antibiotic therapy for ≤4 days

DEFINITIONS OF TERMS USED IN THE DUKE CRITERIA FOR THE DIAGNOSIS OF INFECTIVE ENDOCARDITIS

Major Criteria

  • Positive Blood Culture for Infective Endocarditis
    • Typical microorganism consistent with infective endocarditis from ≥2 separate blood culture: Viridans streptococci, Streptococcus bovis, or HACEK group, community-acquired Staphylococcus aureus or enterococci, in the absence of a primary focus; or
    • Microorganisms consistent with infective endocarditis from persistently positive blood culture defined as:
      • ≥2 positive cultures of blood samples drawn >12 hours apart; or
      • All of 3 or a majority of ≥4 separate blood cultures (regardless of time obtained)
    • Single positive blood culture for Coxiella burnetii or antiphase 1 IgG antibody titer >1:800
  • Evidence of endocardial involvement
    • Positive echocardiogram for infective endocarditis [Transesophageal echocardiography recommended in patients with prosthetic valves, rated at least “possible IE” by clinical criteria, or complicated infective endocarditis (paravalvular abscess); Transthoracic echocardiography as 1st test in other patients] defined as:
      • Oscillating intracardiac mass on valve or supporting structures, in the path of regurgitant jets, or on implanted material in the absence of an alternative anatomic explanation; or
      • Abscess; or
      • New partial dehiscence of prosthetic valve, or
    • New valvular regurgitation (worsening or changing or preexisting murmur not sufficient)

Minor Criteria

  1. Predisposition: predisposing heart condition or IV drug use
  2. Fever: Temp ≥38°C
  3. Vascular phenomena: major arterial emboli, septic pulmonary infarcts, mycotic aneurysm, intracranial hemorrhage, conjunctival hemorrhages, & Janeway lesions
  4. Immunologic phenomena: glomerulonephritis, Osler’s nodes, Roth’s spots & rheumatoid factor
  5. Microbiological evidence: Positive blood culture but does not meet a major criterion as noted above or serological evidence of active infection with organism consistent with infective endocarditis

Modified from: Baltimore RS, Gewitz M, Baddour LM, et al. Infective endocarditis in childhood: 2015 update: a scientific statement from the American Heart Association. Circulation. 2015 Sep 15:8-9.

Physical Examination

  • Heart murmur consistent with valvular regurgitation
  • Petechiae on the skin, conjunctivae or oral mucosa
  • Osler’s nodes: Red, painful, indurated lesions, 2-15 mm in diameter seen on the palms or soles & usually in the digital phalanges
  • Janeway lesions: Non-tender, erythematous macules that appear on the palms or soles
  • “Blue toe syndrome”: Embolization of small vegetation fragments
  • Roth’s spots: Red, retinal hemorrhages with a pale center
  • Splenomegaly
  • Signs of chronic heart faillure

Laboratory Tests

Blood Culture (BC)

  • Most important laboratory test
  • At least 3 blood cultures should be taken at least 1 hour apart & from different venipunctures preferably at the time that body temperature is rising
    • May obtain 2-3 more blood cultures if no growth by 2nd incubation day
  • It is recommended to postpone antimicrobial therapy until blood culture become positive, unless the patient is septic
  • If antimicrobial therapy has been started, wait for at least 3 days after discontinuing short-term antibiotic treatment before taking blood culture
    • If patient was on long-term antibiotic treatment, positive blood culture may not appear until after 6-7 days post-therapy
  • Identification of causative organism should be up to species level

Other Lab Tests

  • Complete blood count with differential
    • Many patients have leukocytosis: 15,000-25,000/muL with a left shift
    • Anemia is common: Normocytic & normochromic with low serum Fe level & TIBC
  • Serum electrolytes: Some patients may have elevated serum creatinine
  • Urinalysis: May reveal microscopic hematuria, pyuria, RBC casts, bacteriuria, proteinuria
  • ESR: Elevated in most cases
  • C-reactive protein level: Elevated
  • Rheumatoid factor: Elevated in approximately half of the presenting patients

Screening

Echocardiogram

  • Diagnostic test of choice in detecting vegetations in cardiac valves

Three Echocardiographic Findings Considered to be Major Criteria in the Diagnosis of Infective Endocarditis

  1. Mobile, echodense mass attached to the valvular or the mural endocardium especially if present on the preferred locations, or attached to implanted prosthetic material with no alternative anatomical explanation
  2. Demonstration of abscesses or fistulas
  3. A new dehiscence of a valvular prosthesis especially when occurring late after implantation

Transthoracic echocardiography (TTE): 2-dimensional transthoracic echocardiography (2-D echo)

  • Vegetation appears as a discrete mobile echogenic mass attached to the valvular surface downstream from a high to low pressure chamber
  • Vegetations ≥2 mm may be visualized, the larger the size, the more likely a vegetation will be detected
  • Transthoracic echocardiography detection rate is approximately 50% in patients with clinically suspected infective endocarditis
  • If the clinical suspicion of infective endocarditis is low, the transthoracic echocardiography is of good quality & the result is negative, endocarditis is unlikely

Transesophageal echocardiography (TEE)

  • Has superior resolution, thus carries a greater sensitivity in detecting vegetations as compared with transthoracic echocardiography although its utility in children is not well established
  • If suspicion of infective endocarditis is high (eg staphylococcal bacteremia), then transesophageal echocardiography should be performed in all negative transthoracic echocardiography cases
  • Transesophageal echocardiography should be performed in all suspected prosthetic valve endocarditis cases, in cases of aortic location & prior to cardiac surgery during active infective endocarditis
  • If transesophageal echocardiography is negative but suspicion of infective endocarditis remains, then repeat transesophageal echocardiography after 48 hours-1 week; this will allow potential vegetations to become more noticeable

Other Diagnostic Studies

Electrocardiogram (ECG)

  • May be taken upon admission in patients with suspected acute infective endocarditis
    • Evidence of low septal abscesses with involvement of the intraventricular conduction system is detected on electrocardiogram
    • Can be used to rule out conduction abnormalities & to establish baseline

Imaging

Chest Radiograph

  • May delineate the presence of chronic heart failure
  • May show septic pulmonary emboli & infiltrates with cavitation that are associated with right-sided infective endocarditis

CT Scan

  • Obtain in any patient with neurologic signs & symptoms
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