When is a transesophageal echocardiogram (TEE) needed for gram-positive bacteremia if the transthoracic echocardiogram (TTE) is negative?

TEE Indications for Gram-Positive Bacteremia with Negative TTE

TEE is recommended when TTE is negative in gram-positive bacteremia if clinical suspicion for infective endocarditis remains high, particularly in the presence of prosthetic valves, intracardiac devices, persistent fever despite appropriate antibiotics, or ongoing bacteremia. 1

High-Risk Features Requiring TEE After Negative TTE

Absolute Indications

• Prosthetic heart valves or intracardiac devices (pacemakers, defibrillators, surgical conduits) - TEE is mandatory regardless of TTE findings 1
• Persistent or recurrent fever despite 48-72 hours of appropriate antibiotic therapy 2
• Ongoing bacteremia after 72 hours of appropriate antibiotics 3
• New conduction abnormalities (heart block, new arrhythmias) suggesting perivalvular extension 1

Strong Indications

• Staphylococcus aureus bacteremia - TEE should be strongly considered even with negative TTE, as sensitivity of TTE is only 21-24% for detecting endocarditis in this population 2, 4, 5
• Previous history of infective endocarditis 1
• New or changing cardiac murmur 1
• Embolic events (stroke, splenic/renal infarcts) of unknown origin 1
• Clinical signs of heart failure 1

Diagnostic Performance Considerations

TTE Limitations in Gram-Positive Bacteremia

• Overall sensitivity of TTE for detecting vegetations is only 58-71% in native valves and 50% in prosthetic valves 1, 6, 5
• In S. aureus bacteremia specifically, TTE sensitivity drops to 21-24%, missing 76-79% of cases 2, 4
• TEE sensitivity is substantially higher at 88-96% for detecting vegetations 1, 2, 4

When TEE May Not Be Necessary

• Good-quality negative TTE with low clinical suspicion - TEE is not indicated 1
• Negative predictive value of a truly negative TTE (native valves with ≤mild regurgitation, no vegetation) is 95-97%, even in S. aureus bacteremia 5
• Isolated right-sided native valve endocarditis with good quality TTE and unequivocal findings 1

Timing of TEE

Initial TEE

• Perform as soon as possible (ideally within 24-48 hours) when high clinical suspicion exists despite negative TTE 1
• Do not delay TEE in S. aureus bacteremia with risk factors, as early detection impacts mortality 2, 4

Repeat TEE

• If initial TEE is negative but clinical suspicion remains high, repeat TEE within 5-7 days (or sooner in S. aureus infection) 1
• Vegetations may be too small initially or develop over time 1
• A repeatedly negative TEE virtually excludes the diagnosis 1

Common Pitfalls to Avoid

Critical Errors

• Relying on TTE alone in S. aureus bacteremia - This misses the majority of cases and is associated with increased mortality 2, 4
• Accepting "equivocal" TTE as negative - Patients with prosthetic valves or >mild regurgitation but no visible vegetation still require TEE, as 19% will have endocarditis 5
• Delaying TEE in high-risk patients - Waiting for clinical deterioration before ordering TEE increases complications and mortality 1, 2

Special Populations

• Elderly or immunocompromised patients may have atypical presentations with less fever, requiring lower threshold for TEE 1
• Gram-positive bacteremia with implanted cardiac devices (permanent pacemakers) has dramatically increased risk (OR 32.3) and mandates TEE even with negative TTE 2

Practical Algorithm

1. All gram-positive bacteremia: Obtain TTE first 1

2. If TTE negative, assess risk factors:

   • High risk (prosthetic valve, device, S. aureus, persistent fever, emboli, new murmur, heart block) → Proceed directly to TEE 1, 2
   • Low risk (no risk factors, good quality TTE, clinical improvement) → TEE not needed 1

3. If TEE negative but suspicion remains high: Repeat TEE in 5-7 days 1

4. If clinical complications develop (new murmur, emboli, heart failure, persistent fever, heart block): Urgent repeat TEE regardless of prior imaging 1