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Infective Endocarditis

 

  • Microbiology:
    • Native valve:
      • S. aureus (30%)
      • Strep viridans (20%)
      • Enterococcus (10%)
      • Coag negative staph (10%)
      • Strep bovis (5%)
    • Prosthetic valve:
      • S. aureus (40%)
      • Coag negative staph (20%)
      • Culture negative (20%)
      • Fungal (10%)
  • Diagnosis: IE results in persistent bacteremia, thus drawing multiple blood cultures is key
    • Duke's criteria: serve as a guide, but do not trump clinical judgement
      • Major:
        • 1. Consistent blood cultures (any of below):
          • Typical organisms in two cultures: S. aureus, Strep viridans, Strep bovis, HACEK, enterococcus
          • Persistently positive cultures consistent with IE:
            • Two cultures, >12h apart, or 3/3, or majority of 4 or more cultures, with one hour between first and last culture
          • Positive culture or IgG for Coxiella burnetti
        • Evidence of endocardial involvement (any of below):
          • New valvular regurgiation (new murmur insufficient)
          • Oscillating intracardiac mass
          • Abscess
          • Dehiscence of prosthetic valve
      • Minor:
        • Fever >38C
        • Vascular phenomena (e.g. emboli, Janeway's lesions)
        • Immunologic phenomena (e.g. glomerulonephritis, Osler's nodes, RF)
        • Blood cultures not meeting major criteria
      • Definite IE: 2 major, 1 major + 3 minor, 5 minor
    • Studies:
      • ECG: may show conduction block
      • CXR: may show septic emboli
      • Echocardiography:
        • TTE: sensitivity 30-60% (30% in S. aureus bacteremia), specificity 100%
          • Sensitivity affected by windows, valvular abnormalities, prothetic valves
          • With totally normal TTE, sensitivity is 95%
        • TEE: more invasive and expensive
          • Incremental value may be in non-diagnostic TTE, or to evaluate prosthetic valves or for abscesses
        • Even if decision to treat for IE is made, echo can provide helpful information (e.g. size of vegetation, extension of infection)
        • In patients with S. aureus bacteremia, such as this case, you cannot hang your hat on a negative TTE
  • Therapy:
    • Prompt initiation of therapy is critical, given high mortality (20-40%, even with modern therapy)
    • Initial therapy should cover MRSA, with vancomycin being drug of choice
      • Daptomycin has only been studied in R-sided endocarditis
    • If MSSA, should narrow to rapidly-cidal anti-staphylococcal agent (e.g. nafcillin or cefazolin)
    • Adjuvant gentamicin clears bactermia more rapidly, but does not change mortality and is nephrotoxic - should only be used for 3-5 days
    • Duration of therapy is typically 6 weeks

 

  • Surgery: indicated if there are complications
    • Heart failure
    • Severe valvular regurgitation
    • Abscess
    • Heart block
    • Persistently positive cultures despite appropriate therapy
    • Fungal endocarditis
    • Embolization
    • Extravalvular extension

 

(Christopher Woo MD, 8/10/10)