What is the sensitivity and specificity of transthoracic echocardiogram (TTE) for diagnosing endocarditis in native, prosthetic, and mechanical valves?

Diagnostic Accuracy of Transthoracic Echocardiography for Endocarditis

Transthoracic echocardiography (TTE) has limited sensitivity for diagnosing endocarditis, with approximately 70% sensitivity for native valves and only 50% for prosthetic/mechanical valves, while specificity remains high at approximately 90% across all valve types. 1

Sensitivity and Specificity by Valve Type

• TTE sensitivity ranges from 40-70% for detecting vegetations in native valve endocarditis, with specificity of approximately 90% 1
• For prosthetic and mechanical valves, TTE sensitivity drops significantly to approximately 50%, while specificity remains high at around 90% 1
• In comparison, transesophageal echocardiography (TEE) demonstrates superior sensitivity (>90%) across all valve types while maintaining similar specificity (91-100%) 2
• TEE is particularly superior for detecting paravalvular complications such as abscesses and pseudoaneurysms 2

Factors Affecting TTE Diagnostic Performance

• TTE sensitivity is particularly limited for small vegetations (<2-3mm), recently embolized vegetations, and in the presence of pre-existing valvular lesions 1
• False positive TTE findings may occur with degenerative valve disease, Libman-Sacks lesions, thrombi, and other non-infectious valve abnormalities 1
• TTE may miss perivalvular complications such as abscesses, particularly in early stages of infection 1
• The negative predictive value of a normal TTE is approximately 97% in patients with native valves, but significantly lower in those with prosthetic valves 3

Clinical Decision Algorithm Based on Valve Type

For Native Valves:

• TTE sensitivity: 40-70% 1
• TTE specificity: ~90% 1
• A negative TTE in patients with normal native valves has a high negative predictive value (95-97%) and may be sufficient to rule out endocarditis in low-risk patients 3
• When using strict negative criteria (considering indeterminate results as positive), sensitivity can be improved 4

For Prosthetic/Mechanical Valves:

• TTE sensitivity: ~50% 1
• TTE specificity: ~90% 1
• Due to the poor sensitivity, a negative TTE cannot reliably exclude endocarditis in prosthetic valves 1
• TEE is mandatory for adequate evaluation of prosthetic valve endocarditis due to its superior sensitivity (90%) 2

Comparison with Other Imaging Modalities

• While TTE has lower sensitivity than TEE, specificities are similar at 91-98% for TTE and 91-100% for TEE 5
• In prosthetic valve endocarditis, combining TTE and CT may show higher sensitivity than TEE alone for periannular complications 2
• FDG-PET/CT has shown promise in identifying cardiovascular implantable electronic device infections with sensitivities ranging from 60-100% and specificities from 86-100% 5

Important Clinical Considerations

• Initial TTE is recommended for all patients with suspected endocarditis, with a positive TTE confirming diagnosis in most cases 1
• Proceed to TEE in situations such as negative or non-diagnostic TTE with persistent clinical suspicion, presence of prosthetic or mechanical valve, or suspected complications 1
• Repeat echocardiography (TTE/TEE) within 5-7 days if initial examination is negative but clinical suspicion remains high 1
• In patients with Staphylococcus aureus bacteremia, a negative TTE still has a high negative predictive value of 95% 3
• For patients with equivocal TTE findings (no vegetation but prosthetic valve or greater than mild native valvular regurgitation), the risk of missed diagnosis is higher (19%) 3