Echocardiographic Evidence of Infective Endocarditis
The three major echocardiographic findings diagnostic of infective endocarditis are: vegetation, abscess or pseudoaneurysm, and new dehiscence of a prosthetic valve 1.
Major Echocardiographic Criteria
The following findings constitute major Duke criteria for IE diagnosis:
- Vegetation: Oscillating intracardiac mass on valve or supporting structures, in the path of regurgitant jets, or on implanted material
- Abscess or pseudoaneurysm: Perivalvular abscess formation or pseudoaneurysm development
- New prosthetic valve dehiscence: Partial dehiscence of prosthetic valve
- New valvular regurgitation: New or worsening valvular insufficiency 2
Diagnostic Performance by Modality
Transthoracic Echocardiography (TTE)
- Native valve vegetations: 70% sensitivity, ~90% specificity 1
- Prosthetic valve vegetations: 50% sensitivity 1
- Perivalvular abscess: 28% sensitivity 3
Transesophageal Echocardiography (TEE)
- Native valve vegetations: 96% sensitivity, ~90% specificity 1
- Prosthetic valve vegetations: 92% sensitivity 1
- Perivalvular abscess: 87% sensitivity 3
TEE is significantly superior to TTE, particularly for prosthetic valves where transthoracic images are severely limited by prosthetic material 2.
High-Risk Echocardiographic Features
Vegetations >10 mm and mobile vegetations are associated with significantly higher embolic risk 4, 5. In one study, mobile vegetations >10 mm showed 7-fold increased odds of embolization compared to non-mobile vegetations ≤10 mm 4. Patients with vegetation diameter >10 mm had significantly higher embolic event rates (22/47 vs 11/58, p<0.01) 5.
Additional high-risk features include:
- Large or mobile vegetations
- Severe valvular insufficiency
- Perivalvular extension (abscess, pseudoaneurysm, fistula)
- Secondary ventricular dysfunction 2
Diagnostic Pitfalls and False Results
False Negatives
- Small vegetations (<2-3 mm)
- Recent embolization (vegetation may have detached)
- Early disease: Perivalvular abscesses may appear only as nonspecific thickening initially, requiring repeat imaging after several days to identify cavity formation 2
- Non-vegetant IE
- Device-related IE: Particularly challenging even with TEE 1
False Positives
Echocardiographic findings must be interpreted cautiously, as several conditions mimic IE vegetations 1:
- Lambl's excrescences
- Valve fibroelastoma
- Thrombi
- Degenerative or myxomatous valve disease
- Systemic lupus (Libman-Sacks) lesions
- Marantic vegetations
- Chordal rupture or cusp prolapse
Clinical Application Algorithm
Start with TTE in all suspected IE cases 1, 2. Then proceed based on:
If TTE is positive but low complication risk: Medical management may proceed without immediate TEE (exception: prosthetic valves always require TEE) 2
If TTE is negative or non-diagnostic AND high clinical suspicion: Proceed immediately to TEE 1, 2
If initial imaging is negative but high suspicion persists: Repeat TTE and/or TEE within 5-7 days 1
TEE is mandatory for:
- Prosthetic heart valves or intracardiac devices 1
- High clinical suspicion despite negative TTE 1
- Suspected complications (new murmur, embolism, persistent fever, heart failure, abscess, atrioventricular block) 1
Special consideration: In isolated right-sided native valve IE with good quality TTE and unequivocal findings, TEE may not be mandatory 1.
The sensitivity of echocardiography improves significantly when both TTE and TEE are utilized complementarily, with TEE being essential for detecting perivalvular complications and in prosthetic valve cases where TTE is inadequate 2.