Does it make sense to confirm mural endocarditis with cardiac MRI in a patient with suspected infective endocarditis and a flagellated mass in the left atrium?

Cardiac MRI for Confirming Mural Endocarditis

Cardiac MRI has limited utility for confirming mural endocarditis and should not be routinely used, as echocardiography (particularly TEE) remains the diagnostic standard with superior evidence and guideline support. 1

Evidence Base for Cardiac MRI

The evidence supporting cardiac MRI in infective endocarditis is notably weak:

• Limited sensitivity: MRI detected only 14 out of 16 (87.5%) valvular vegetations >7-9.5 mm when compared with echocardiography, with one vegetation missed due to prosthetic valve artifact 1
• Sparse literature: The ACR Appropriateness Criteria explicitly state there is "limited evidence in the literature for the use of MRI of the heart in suspected infective endocarditis" 1
• No guideline endorsement: Cardiac MRI is not included in any major diagnostic algorithms or criteria (Modified Duke Criteria) for endocarditis 1

Recommended Diagnostic Approach for Mural Endocarditis

First-Line Imaging

Transthoracic echocardiography (TTE) should be performed initially in all suspected cases, as it is the only imaging criterion included in the Modified Duke criteria 1, 2

Second-Line Imaging

Transesophageal echocardiography (TEE) is the procedure of choice when:

• TTE is nondiagnostic or suboptimal 3
• Clinical suspicion remains intermediate to high 1
• A flagellated mass in the left atrium requires detailed characterization 2, 4

TEE demonstrates approximately 99% sensitivity for native valve endocarditis and 90% for prosthetic valve endocarditis, significantly outperforming TTE 2

Third-Line Imaging (When Echocardiography is Inconclusive)

Cardiac CT angiography adds value when echocardiography findings are equivocal, particularly for:

• Assessing perivalvular tissues, abscesses, fistulas, and pseudoaneurysms 1
• Surgical planning when complications are suspected 1
• 100% sensitivity/specificity for vegetations >1 cm 3

FDG PET/CT should be considered when:

• Anatomical imaging (echo or CT) is inconclusive or equivocal 1
• Prosthetic material is present (increased diagnostic accuracy from 70% to 97% when added to Modified Duke criteria) 1
• Early detection of inflammatory cells before morphological damage occurs 1

Clinical Context: Left Atrial Mural Endocarditis

For your specific scenario with a flagellated mass in the left atrium:

• TEE is mandatory for detailed characterization of the mass, its attachment site, mobility, and associated complications 2, 4
• Mural endocarditis is rare and diagnostically challenging, often occurring with or without valvular involvement 5, 4, 6, 7
• Multiple imaging modalities may be needed: one case series used TEE followed by cardiac CT angiography and cardiac MRI to fully characterize left atrial mural endocarditis 4
• Multidisciplinary endocarditis team evaluation is recommended for complex cases like mural endocarditis to ensure appropriate diagnosis and surgical timing 4

Key Pitfalls to Avoid

• Do not rely on MRI as a confirmatory test when echocardiography is available and adequate 1
• Do not stop at negative TTE in intermediate-to-high probability cases; proceed directly to TEE 1, 2
• Do not delay repeat imaging if initial high-quality TEE is negative but clinical suspicion remains high; repeat TEE after 3-10 days 2
• Recognize that mural endocarditis can be missed on initial imaging due to unusual location and absence of typical risk factors 5, 6

Bottom Line

For a flagellated mass in the left atrium with suspected mural endocarditis, proceed with TEE as the definitive diagnostic test, not cardiac MRI. If TEE findings remain equivocal despite high clinical suspicion, cardiac CT angiography or FDG PET/CT should be the next step, not MRI. 1, 2, 4