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 sensitivity of 70% 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

Native Valves

• TTE sensitivity ranges from 40-70% for detecting vegetations in native valve endocarditis 1
• TTE specificity is approximately 90% for native valve endocarditis 1
• A negative TTE in patients with normal native valves has a high negative predictive value (95-97%), potentially ruling out endocarditis in low-risk patients 2, 3

Prosthetic Valves

• TTE sensitivity is significantly lower at approximately 50% for prosthetic valve endocarditis 1
• TTE specificity remains high at around 90% for prosthetic valves 1
• The diagnostic yield is particularly limited by acoustic shadowing from prosthetic materials 4

Mechanical Valves

• TTE sensitivity is similarly low at approximately 50% for mechanical valve endocarditis 1
• TTE specificity remains around 90% for mechanical valves 1
• TTE has significant limitations in visualizing mechanical valve leaflet excursions and detecting valve dehiscence 4

Comparison with Transesophageal Echocardiography (TEE)

• TEE is significantly more sensitive than TTE across all valve types, with sensitivity of 96% for native valves and 92% for prosthetic/mechanical valves 1
• TEE specificity is comparable to TTE at approximately 90-100% across all valve types 1
• In prosthetic valve endocarditis, TEE is mandatory due to the poor sensitivity of TTE (50% vs 92%) 1, 4
• TEE is particularly superior for detecting paravalvular complications such as abscesses and pseudoaneurysms 1

Clinical Decision Algorithm

1. Initial TTE for all patients with suspected endocarditis 1

   • If TTE is positive (vegetation clearly identified): Diagnosis confirmed 1
   • If TTE is negative in a patient with normal native valves and low clinical suspicion: Endocarditis can be reasonably excluded (NPV 95-97%) 2, 3

2. Proceed to TEE in the following situations 1:

   • Negative or non-diagnostic TTE with persistent clinical suspicion
   • Presence of prosthetic or mechanical valve (regardless of TTE findings)
   • Suspected complications (abscess, perforation, etc.)
   • Poor quality TTE images

3. Repeat echocardiography (TTE/TEE) within 5-7 days if initial examination is negative but clinical suspicion remains high 1

Important Limitations and Pitfalls

• TTE sensitivity has improved with contemporary technology but remains suboptimal, especially for prosthetic valves 5
• 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

Conclusion

TTE serves as a reasonable initial screening tool for native valve endocarditis with good specificity but limited sensitivity. For prosthetic and mechanical valves, TTE sensitivity is poor (approximately 50%), making TEE mandatory when endocarditis is clinically suspected in these patients. The high negative predictive value of a normal TTE in patients with normal native valves may allow clinicians to avoid TEE in selected low-risk patients.