Obtain an Echocardiogram to Rule Out Bacterial Endocarditis in Gram-Positive Bacteremia
Mike Faulkner MD
Bacterial endocarditis is an uncommon condition with significant morbidity and mortality. The classic clinical triad of bacteremia, valvular pathology, and peripheral embolic phenomena unfortunately only presents in a minority of affected individuals. Cardiac imaging with echocardiography has enhanced the ability to diagnose infective endocarditis, currently comprising one of the major criteria in the Duke clinical criteria for diagnosis of the disorder (Fig. 276.1).
What to Do
In patients with low clinical suspicion and low initial risk (fever, previous heart murmur, no peripheral stigmata), transthoracic echocardiography (TTE) is a reasonable initial screening test. TTE is noninvasive and has an excellent specificity for vegetations (98%). Unfortunately, TTE has relatively poor sensitivity for diagnosing infective endocarditis, detecting approximately 60% of native valve infections and 20% of prosthetic valve infections. It poorly resolves lesions less than 2 mm or lesions of the left heart. In addition, a significant number of patients may suffer from conditions such as chronic obstructive pulmonary disease or obesity that make imaging technically difficult. The limited resolution of TTE also hinders diagnosing complications of infective endocarditis such as valvular leaflet perforations, perivalvular abscesses, and intracardiac fistulae.
Transesophageal echocardiography (TEE) may be indicated as an initial imaging technique in high-risk patients (prosthetic valves, congenital heart disease, previous endocarditis, newmurmur, heart failure, or other stigmata of endocarditis) or in patients with moderate to high clinical suspicion of infective endocarditis. TEE is a more invasive technique, but it allows placement of the echo transducer closer to the valvular structures of the heart. Sensitivity of TEE has been reported to be greater than 90% in detecting vegetations. Detailed imaging of complications from infective endocarditis such as perivalvular abscess is also enhanced by the transducer’s proximity to cardiac structures.