Can cardiac MRI (Magnetic Resonance Imaging) be used to evaluate endocarditis?

Role of Cardiac MRI in Evaluating Endocarditis

Cardiac MRI can be used as a complementary imaging modality for evaluating endocarditis, particularly when echocardiography is inconclusive or nondiagnostic, but it should not be used as the first-line imaging test. 1

Primary Imaging Approach for Endocarditis

1. First-line imaging:

   • Transthoracic echocardiography (TTE) is the initial imaging test of choice for suspected endocarditis
   • Transesophageal echocardiography (TEE) is indicated for patients with intermediate or high probability of endocarditis, or when TTE is suboptimal

2. When to consider cardiac MRI:

   • When TTE/TEE results are inconclusive or nondiagnostic
   • For better evaluation of specific complications of endocarditis
   • For quantification of valvular regurgitation when echocardiography is suboptimal

Strengths of Cardiac MRI in Endocarditis Evaluation

• Complication assessment: MRI excels at evaluating complications such as:

  • Paravalvular and myocardial abscesses
  • Pseudoaneurysms
  • Fistulas
  • Endothelial inflammation before morphological changes develop 1

• Regurgitation quantification: MRI can accurately quantify valvular regurgitation in cases where:

  • Echocardiography is suboptimal
  • There is discordance between anatomic and Doppler findings
  • Eccentric jets are present, which are harder to accurately quantify by echocardiography 1

• Inflammatory extension: MRI can detect delayed enhancement representing endothelial inflammation of cardiovascular structures, which can contribute to diagnosis and treatment planning even in the absence of vegetations 2

Limitations of Cardiac MRI for Endocarditis

• Vegetation detection: MRI is less accurate than TTE and TEE for identifying valvular vegetations 1

  • One study showed MRI detected 87.5% of vegetations >9.5mm but missed smaller ones 2
  • Limited spatial resolution compared to echocardiography 3

• Practical considerations:

  • Longer examination time
  • Contraindicated in patients with certain implanted devices
  • Limited availability in emergency settings
  • Higher cost compared to echocardiography

Clinical Algorithm for Imaging in Endocarditis

1. Initial evaluation: Perform TTE in all patients with suspected endocarditis
2. If TTE is positive and diagnostic: Proceed with treatment
3. If TTE is negative or inconclusive:
   • For native valves: Proceed to TEE
   • For prosthetic valves or cardiac devices: Proceed to TEE
4. If TEE is inconclusive or nondiagnostic:
   • Consider cardiac MRI for:
     • Evaluation of paravalvular extension
     • Assessment of myocardial involvement
     • Quantification of valvular regurgitation
   • Consider CT or PET/CT (especially for prosthetic valves)

Important Caveats

• Do not delay appropriate antibiotic therapy while awaiting advanced imaging
• Cardiac MRI should not replace echocardiography as the first-line imaging test
• The diagnostic yield of cardiac MRI is highest when used as a complementary test to echocardiography
• Negative findings on cardiac MRI do not exclude the diagnosis of endocarditis if clinical suspicion remains high

By following this approach, cardiac MRI can provide valuable additional information in selected cases of suspected endocarditis, potentially improving diagnostic accuracy and guiding management decisions.