What is the role of Transesophageal Echocardiography (TOE) in a pediatric patient with congenital restrictive cardiomyopathy due to endocardial fibroelastosis (EFE)?

Role of Transesophageal Echocardiography in Pediatric Restrictive Cardiomyopathy Due to Endocardial Fibroelastosis

TOE should be reserved for cases where transthoracic echocardiography (TTE) fails to provide adequate diagnostic information, particularly when surgical planning requires precise delineation of endocardial thickening extent or when acoustic windows are severely limited. 1

Primary Imaging Approach

• TTE remains the first-line imaging modality for pediatric patients with suspected or confirmed endocardial fibroelastosis (EFE), as it is non-invasive, widely available, and generally provides adequate visualization in children 1

• Standard TTE can demonstrate the characteristic findings of EFE including left ventricular globular dilatation, endocardial thickening (though often subtle), systolic dysfunction, and abnormal ventricular wall motion 2

• However, TTE has significant limitations in EFE: echocardiography demonstrated only mild endocardial brightening in 2 of 3 surgically-confirmed EFE cases in one study, with no study considered diagnostic of endocardial fibrosis 3

Specific Indications for TOE in EFE

TOE is indicated when TTE cannot provide sufficient diagnostic information needed for clinical decision-making, specifically in the following scenarios 1:

Class I Indications (Strongly Recommended)

• When significant diagnostic information cannot be obtained by TTE in any patient with congenital or acquired heart disease, including restrictive cardiomyopathy 1

• Perioperative monitoring and guidance during surgical resection of EFE, particularly for assessing:

  • Completeness of endocardial resection 1
  • Residual valvular insufficiency (especially mitral regurgitation) 1
  • Ventricular function and volume status during weaning from cardiopulmonary bypass 4

• Chest wall disruptions from previous cardiac surgery that limit TTE acoustic windows 1

• Congenital anomalies of the thoracic cage that prevent adequate TTE visualization 1

Anatomic Advantages of TOE in EFE

TOE provides superior visualization of structures critical to EFE assessment 1, 4:

• Detailed evaluation of left ventricular endocardium, particularly the posterior and lateral walls where EFE characteristically occurs 4

• Precise assessment of mitral valve morphology and function, as mitral regurgitation commonly accompanies EFE due to papillary muscle involvement 4

• Superior imaging of the left ventricular outflow tract for associated subaortic obstruction 4

• Excellent resolution of atrial structures and systemic venous return 4

Important Limitations of TOE in Pediatric EFE

Technical Constraints

• Minimum body weight requirements exist: probes ≥13mm diameter require 17-20 kg body weight; 11mm probes require approximately 12 kg; only 7mm probes can be safely used in neonates and small infants 5

• Blind spots persist even with TOE: the apical interventricular septum and apex (where EFE may extend) remain difficult to visualize with single-plane transesophageal imaging 4

Procedural Considerations

• General anesthesia or deep sedation is required in pediatric patients, adding procedural risk and complexity 4, 5

• Potential for airway compromise exists, particularly in infants and young children with already compromised cardiac function 1

• Requires experienced operators: TOE should not be performed by novice practitioners, especially in hemodynamically unstable patients 6

Superior Alternative: Cardiac MRI

Cardiac MRI has emerged as the superior non-invasive modality for definitive diagnosis and functional assessment of EFE, and should be strongly considered before proceeding to TOE 2, 3:

MRI Advantages Over Both TTE and TOE

• Perfusion sequences demonstrate EFE as a hypointense endocardial rim, providing specific tissue characterization not possible with echocardiography 3

• Delayed gadolinium enhancement shows EFE as a hyperintense endocardial rim, definitively establishing the diagnosis 3

• MRI-measured ejection fraction and fractional shortening correlate significantly better with clinical cardiac function scores than echocardiographic measurements (EF correlation: r=0.646 vs 0.224; FS correlation: r=0.627 vs 0.245) 2

• MRI provides more accurate ventricular volume and function measurements without geometric assumptions that limit echocardiography 2

• MRI is not affected by body habitus, thoracic deformities, or post-surgical changes that degrade echocardiographic image quality 1

When MRI Should Replace TOE Consideration

• For diagnostic confirmation of EFE when TTE findings are equivocal or non-diagnostic 2, 3

• For preoperative surgical planning to delineate the extent of endocardial fibrosis 3

• For serial functional assessment in patients old enough to undergo MRI without sedation (typically >6-8 years) 1

Clinical Algorithm for Imaging Selection in Pediatric EFE

1. Initial assessment: Perform TTE in all suspected cases 1

2. If TTE is diagnostic and provides adequate information for management: Continue TTE for serial monitoring 1

3. If TTE is non-diagnostic or equivocal:

   • First choice: Cardiac MRI (if patient age/size permits and no contraindications exist) 2, 3
   • Second choice: TOE (if MRI unavailable, contraindicated, or immediate intraoperative assessment needed) 1

4. Intraoperatively during EFE resection: TOE for real-time surgical guidance and immediate post-repair assessment 1, 4

Common Pitfalls to Avoid

• Do not rely solely on TTE for surgical planning in EFE, as it frequently underestimates the extent of endocardial involvement 2, 3

• Do not perform TOE in infants <12 kg without a dedicated 7mm pediatric probe, as larger probes cannot be safely inserted 5

• Do not assume TOE will visualize all cardiac structures: the apex and apical septum remain poorly seen even with transesophageal approach 4

• Do not order TOE when cardiac MRI would provide superior diagnostic information and the clinical situation is not emergent 2, 3