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TTE appears viable for managing low-risk S. aureus bacteremia
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A normal transthoracic echocardiogram, or TTE, ruled out infective endocarditis in patients with low-risk Staphylococcus aureus bacteremia, according to recent results.
Current guidelines recommend performing transesophageal echocardiography or treatment with prolonged IV antibiotics for any patient with S. aureus, as this can often lead to infective endocarditis, according to the study background. However, the researchers wrote, this approach is resource-intensive and many physicians do not follow it, so they investigated whether TTE could be used to adequately rule out infective endocarditis in low-risk patients.
Adrienne Showler, MD, and colleagues conducted a retrospective cohort study of 833 consecutive patients who were hospitalized with S. aureus bacteremia. The 536 patients who received a TTE within 28 days of bacteremia were randomly divided into derivation and validation cohorts.
The researchers used multivariable logistic regression analysis to identify high-risk criteria for infective endocarditis in the derivation cohort and applied these criteria to the validation cohort to evaluate their diagnostic properties.
They classified the bacteremia as nosocomial (33.7%), health care-associated (36.9%) or community-acquired (27.6%); 17% of patients had MRSA and 8.4% had a high-risk cardiac condition.
Showler, from the department of medicine and the division of infectious diseases at University of Toronto, and colleagues identified four high-risk criteria that predicted infective endocarditis: indeterminate or positive TTE (P < .001), community-acquired bacteremia (P = .034), IV drug use (P < .001) and a high-risk cardiac condition (P < .004).
When they applied the criteria to the validation cohort, they found that the presence of any one of these criteria had 97% sensitivity (95% CI, 87-100) and a negative predictive value of 99% (95% CI, 96-100) for infective endocarditis, with a negative likelihood ratio was 0.05 (95% CI, 0.007-0.35). Patients with more than one criterion were at a further increased risk for infective endocarditis, the researchers wrote.
“A normal TTE ruled out [infective endocarditis] in patients without community-acquired [S. aureus bacteremia], [IV] drug use and high-risk cardiac conditions,” Showler and colleagues concluded. “Our criteria provide evidence that in low-risk patients with [S. aureus bacteremia], a TTE is adequate to exclude [infective endocarditis], which could decrease the use of invasive tests and provide more efficient patient care.” – by Erik Swain
Disclosure: Showler reports no relevant financial disclosures. One researcher reports receiving salary support via an educational grant from Pfizer Canada. Another researcher reports serving on the advisory board of Cubist Pharmaceuticals.
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