What are the indications for an echocardiogram (echo) in patients with bacteremia?

Indications for Echocardiography in Bacteremia

Echocardiography should be performed in all patients with bacteremia who have high-risk features for infective endocarditis, with the specific organism and clinical context determining the urgency and modality (TTE vs TEE). 1

Mandatory Echocardiography Indications

High-Risk Organisms

• Staphylococcus aureus bacteremia warrants echocardiography in nearly all cases due to the 25% risk of developing infective endocarditis and associated mortality of 25-46%. 1, 2, 3
• Start with transthoracic echocardiography (TTE) as first-line imaging, though it has only 32-63% sensitivity for detecting endocarditis in S. aureus bacteremia. 2, 3
• Transesophageal echocardiography (TEE) should follow if TTE is negative or non-diagnostic, as TEE increases sensitivity to 88-100% for detecting vegetations and complications. 2, 3

High-Risk Clinical Features (Any Organism)

• Prosthetic heart valves or intracardiac devices (pacemakers, defibrillators) require TEE regardless of initial TTE findings, as these patients have a 16-32% risk of endocarditis. 1, 4, 2, 5
• Persistent fever or bacteremia despite appropriate antibiotic therapy for 48-72 hours mandates repeat imaging to detect complications. 1, 2
• New or changing cardiac murmur detected on examination requires immediate echocardiography. 1, 4
• Embolic events (stroke, splenic infarct, peripheral emboli) indicate possible cardiac source and warrant urgent imaging. 1, 4
• Signs of heart failure (new dyspnea, pulmonary edema, gallop rhythm) require echocardiography to assess valvular function and ventricular performance. 1, 4
• Previous history of infective endocarditis significantly increases risk and mandates imaging. 4

Risk-Stratified Approach by Organism

Staphylococcus aureus Bacteremia

• Community-acquired infection, prolonged bacteremia (>48 hours), or intracardiac prosthetic devices all require TEE after initial TTE. 6, 5
• Very low-risk patients (nosocomial/line-related infection, no prosthetic valves/devices, bacteremia cleared within 48 hours, no clinical signs of endocarditis) may have echocardiography deferred with close clinical monitoring, as the yield is <5% in this subset. 7, 6, 5
• However, even in low-risk patients, the absolute survival benefit of echocardiography is minimal (<0.5%), making clinical judgment paramount. 7

Other Gram-Negative Organisms (e.g., Enterobacter cloacae)

• Not all bacteremias require routine echocardiography—individualized assessment based on high-risk features is appropriate for organisms other than S. aureus. 4
• Order TTE initially if any high-risk features are present: prosthetic valves, intracardiac devices, persistent fever, new murmur, embolic events, heart failure, or immunocompromised status. 4
• Elderly and immunocompromised patients may have atypical presentations with less prominent fever, requiring a lower threshold for imaging. 4

Echocardiography Protocol

Initial Imaging

• TTE is the first-line modality with 70% sensitivity for native valve vegetations but only 50% for prosthetic valves. 1, 4
• Perform TTE as soon as infective endocarditis is suspected, ideally within 24-48 hours of positive blood cultures in high-risk cases. 1

When to Proceed to TEE

• TTE is negative but clinical suspicion remains high based on persistent fever, positive blood cultures, or high-risk organism. 1
• TTE is non-diagnostic or suboptimal quality (obesity, COPD, mechanical ventilation). 1, 4
• Prosthetic valve or intracardiac device is present, as TTE has poor sensitivity in these patients. 1, 4
• TTE is positive for vegetations to evaluate for complications such as abscesses, perforations, or shunts that impact surgical decision-making. 1
• Repeat TEE within 5-7 days if initial examination is negative but clinical suspicion remains high. 1

Reassessment During Treatment

Indications for Repeat Imaging

• New complications develop: new murmur, embolic event, persistent fever, heart failure, atrioventricular block, or clinical deterioration. 1
• Complex endocarditis (virulent organism like S. aureus, severe hemodynamic lesion, aortic valve involvement) warrants repeat imaging to monitor vegetation size and detect silent complications. 1

When Repeat Imaging is NOT Indicated

• Uncomplicated native valve endocarditis with no regurgitation on baseline echocardiogram, responding well to antibiotics without clinical deterioration, new physical findings, or persistent fever does not require routine repeat TTE. 1

Common Pitfalls to Avoid

• Do not rely solely on TTE in patients with prosthetic valves or intracardiac devices—TEE is mandatory as TTE sensitivity is only 50% in this population. 1, 4
• Do not delay TEE in S. aureus bacteremia with negative TTE—19-21% of patients with negative or indeterminate TTE will have endocarditis detected on TEE. 3
• Do not assume line-related bacteremia excludes endocarditis—while risk is lower, patients with prosthetic material or persistent symptoms still require imaging. 5
• Do not order echocardiography for transient fever without bacteremia or new murmur—this is a Class III indication (not recommended). 1