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When does S aureus bacteremia require transesophageal echocardiography?

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Staphylococcus aureus is the most common infective agent in native and prosthetic valve endocarditis, and 13% to 22% of patients with S aureus bacteremia have infective endocarditis.1

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Transthoracic echocardiography (TTE) is a good starting point in the workup of suspected infective endocarditis, but transesophageal echocardiography (TEE) plays a key role in diagnosis and is indicated in patients with a high pretest probability of infective endocarditis, as in the following scenarios:

  • Clinical picture consistent with infective endocarditis
  • Presence of previously placed port or other indwelling vascular device
  • Presence of a prosthetic valve or other prosthetic material
  • Presence of a pacemaker
  • History of valve disease
  • Injection drug use
  • Positive blood cultures after 72 hours despite appropriate antibiotic treatment
  • Abnormal TTE result requiring better visualization of valvular anatomy and function and confirmation of local complications
  • Absence of another reasonable explanation for S aureus bacteremia.

Forgoing TEE is reasonable in patients with normal results on TTE, no predisposing risk factors, a reasonable alternative explanation for S aureus bacteremia, and a low pretest probability of infective endocarditis.1 TEE may also be unnecessary if there is another disease focus requiring extended treatment (eg, vertebral infection) and there are no findings suggesting complicated infective endocarditis, eg, persistent bacteremia, symptoms of heart failure, and conduction abnormality.1

TEE also may be unnecessary in patients at low risk who have identifiable foci of bacteremia due to soft-tissue infection or a newly placed vascular catheter and whose bacteremia clears within 72 hours of the start of antibiotic therapy. These patients may be followed clinically for the development of new findings such as metastatic foci of infection (eg, septic pulmonary emboli, renal infarction, splenic abscess or infarction), the new onset of heart failure or cardiac conduction abnormality, or recurrence of previously cleared S aureus bacteremia. If these should develop, then a more invasive study such as TEE may be warranted.

INFECTIVE ENDOCARDITIS: EPIDEMIOLOGY AND MICROBIOLOGY

The US incidence rate of infective endocarditis has steadily increased, with an estimated 457,052 hospitalizations from 2000 to 2011. During that period, from 2000 to 2007, there was a marked increase in valve replacement surgeries.2 This trend is likely explained by an increase in the at-risk population—eg, elderly patients, patients with opiate dependence or diabetes, and patients on hemodialysis.

Although S aureus is the predominant pathogen in infective endocarditis,2–5S aureus bacteremia is often observed in patients with skin or soft-tissue infection, prosthetic device infection, vascular graft or catheter infection, and bone and joint infections. S aureus bacteremia necessitates a search for the source of infection.

S aureus is a major pathogen in bloodstream infections, and up to 14% of patients with S aureus bacteremia have infective endocarditis as the primary source of infection.3 The pathogenesis of S aureus infective endocarditis is thought to be mediated by cell-wall factors that promote adhesion to the extracellular matrix of intravascular structures.3

A new localizing symptom such as back pain, joint pain, or swelling in a patient with S aureus bacteremia should trigger an investigation for metastatic infection.

Infectious disease consultation in patients with S aureus bacteremia is associated with improved outcomes and, thus, should be pursued.3

A cardiac surgery consult is recommended early on in cases of infective endocarditis caused by vancomycin-resistant enterococci, Pseudomonas aeruginosa, and fungi, as well as in patients with complications such as valvular insufficiency, perivalvular abscess, conduction abnormalities, persistent bacteremia, and metastatic foci of infection.6

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S aureus bacteremia: TEE and infectious disease consultation

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