Endocarditis

Chief's Pearl

 This week we will review the diagnostic criteria for INFECTIOUS ENDOCARDITIS.  Now that children with congenital heart disease have much improved survival rates, and with the overall decrease in rheumatic valvular heart disease in developed countries, CHD now constitutes the predominant underlying condition for IE in children over 2 years of age.  In about 8-10% of cases, IE develops without structural heart disease or other identifiable risk factors, i.e. indwelling catheters, and usually involves infection of the aortic or mitral valve due to Staph aureus bacteremia.  In terms of congenital heart disease, any lesion associated with TURBULENT flow, with or without shunting, can be a substrate for IE, i.e. VSD, PDA, aortic valve anomaly, TOF.

        The diagnosis of IE is based on the DUKE CRITERIA:
Major Criteria

• Positive blood culture for IE
  • Typical micro-organism consistent with IE from 2 separate blood cultures as noted below:
    1. Viridans streptococci, Streptococcus bovis, or HACEK group, or    
    2. Community-acquired Staph aureus or enterococci, in the absence of a primary focus or       
  •  Micro-organisms consistent with IE from persistently positive blood cultures defined as
    1. >/= 2 positive cultures of blood samples drawn >12 hours apart or
    2. All of 3 or a majority of >/=4 separate cultures of blood (with first and last sample drawn >/= 1hr apart)
• Evidence of endocardial involvement
  • Positive echocardiogram for IE 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 of preexisting murmur not sufficient)

Minor Criteria
1) Predisposition: predisposing heart condition or IV drug use
2) Fever: temp >/= 38.0 C
3) Vascular phenomena: major arterial emboli, septic pulmonary infarcts, mycotic aneurysm, intracranial hemorrhage, conjunctival hemorrhages, and Janeway lesions

4) Immunologic phenomena: glomerulonephritis, Osler nodes, Roth's spots, and 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 IE

6) Echocardiographic findings: consistent with IE but do not meet a major criterion as noted above

Definite IE:
Clinical criteria:
        2 major criteria, or
        1 major criterion and 3 minor criteria, or
        5 minor criteria
Pathological criteria:
        > Micro-organisms: demonstrated by culture or histology in a vegetation, a vegetation that has embolized, or an intracardiac abscess, or

        > Pathological lesions: vegetation or intracardiac abscess present, confirmed by histology showing active endocarditis

Possible IE:
Findings consistent with IE that fall short of "definite" but not "rejected"

Rejected:

• Firm alternative diagnosis for manifestations of endocarditis, or
• Resolution of manifestations of endocarditis with antibiotic therapy for </= 4 days, or
• No pathological evidence of IE at surgery or autopsy, after antibiotic therapy for </= 4 days

You can find the entire article titled, "Unique Features of Infective Endocarditis in Childhood" in Pediatrics, May 2002, or from the American Heart Association.  Because of all of the CHD we see here, this is something we need to keep in mind.  We hope this helps.

===

Of the following, the finding that is MOST indicative of bacterial endocarditis in an adolescent who has mitral valve prolapse is

• blood culture positive for Streptococcus viridans
• echocardiographic evidence of valve thickening and redundancy
• fever and splenomegaly
• microscopic hematuria
• mitral regurgitation murmur and fever

Documentation of bacteremia caused by a typical pathogen such as one of the viridans streptococcal organisms is a conclusive indication of endocarditis associated with mitral valve prolapse in an adolescent. (Answer A)

In addition to the American Heart Association-accepted criterion of mitral valve regurgitation, echocardiographic evidence of mitral valve redundancy and thickening is a possible risk factor for endocarditis. Increased thickening of the valve may represent early vegetation formation in the presence of bacterial endocarditis, but in isolation, it does not constitute definitive evidence of endocarditis.

Fever and splenomegaly also occur in patients who have bacterial endocarditis; splenomegaly is more common in patients who have had fever and bacteremia for weeks (subacute bacterial endocarditis). However, these findings also are typical manifestations of infectious mononucleosis, a diagnosis that is much more common in adolescence than infectious endocarditis.

Microscopic hematuria is a well-described finding in many patients who have subacute or long-standing endocarditis. It represents a form of glomerulonephritis from immune complex deposition and is associated with low circulating complement levels. However, there are other more common causes of microscopic hematuria in an adolescent female, such as urinary tract infection.

Many patients who have mitral valve prolapse also have mitral valve regurgitation. It is believed that these patients are at a significantly higher risk to develop bacterial endocarditis than mitral prolapse patients who do not have valvular regurgitation, but the occurrence of fever in such patients is not diagnostic of endocarditis.

Pericarditis, Bacterial

References:
Bayer AS, Bolger AF, Taubert KA, et al. American Heart Association. AHA scientific statement. Diagnosis and management of infective endocarditis and its complications. 1998. Available at:
Bonow RO, Carabello B, de Leon AC Jr, et al. ACC/AHA guidelines for the management of patients with valvular heart disease: a report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines (Committee on Management of Patients With Valvular Heart Disease). J Am Coll Cardiol. 1998;32:1486-1588
Brook MM. Pediatric bacterial endocarditis. Treatment and prophylaxis. Pediatr Clin North Am. 1999;46:275-287