When RV dysfunction in Ebsteins complicates diagnostic interpretation of right outflow obstruction

Description of Clinical Presentation: A 15-year-old male with Ebstein anomaly had initially undergone a bidirectional Glenn procedure and main pulmonary artery (MPA) banding at 11 months, followed by Cone procedure, ASD closure, MPA debanding and arterioplasty at 6 years. He remained well with persistent RV dysfunction attributed to the atrialized portion of the RV. He presented to the clinic with exertional chest pain and easy fatigue compared to his peers. His echocardiogram found trivial tricuspid regurgitation, a mild gradient across his RV outflow tract (35 mmHg) and moderate pulmonary regurgitation with RV dilation and severely decreased RV systolic function. He was referred for CMR to assess his RV function and pulmonary regurgitant fraction.

Diagnostic Techniques and Their Most Important Findings: CMR found increased RVEDV and RVESV, 174 ml/m2 (z-score 4.25) and 134 ml/m2 (z-score 6.18), respectively with significantly reduced RVEF = 23% which included a large dyskinetic atrialized portion of the RV. LV volumes and LVEF (62%) were normal. There was no pulmonary stenosis and only minimal pulmonary regurgitation (RF 7%).The pulmonary annulus was normal (24 mm) but the MPA was irregular with a discrete narrowing and infolding on the inferior surface resulting in significant supravalvar pulmonary stenosis (12 mm). Both pulmonary artery branches were unobstructed. Subsequent to these findings, he underwent MPA patch arterioplasty and removal of a fibrous ring that was found encroaching around the circumference of the MPA.

Learning Points from this Case: Ebstein’s anomaly presents unique diagnostic challenges, particularly when right ventricular dysfunction appears disproportionate in relation to clinical severity and imaging findings. We describe a case of Ebsteins with persistent RV dysfunction after a Cone procedure, leading to an under-recognition of the severity of supravalvar pulmonary stenosis. CMR was diagnostic in defining the RV outflow tract anatomy showing that gradients can underestimate the degree of obstruction. Not all RV dysfunction in Ebsteins should be attributed to the atrialized RV and separate assessments of the true RV and the atrialized RV should be performed as well as investigating for other anatomical contributors to RV dysfunction. This case highlights the anatomical and functional complexities that contribute to diagnostic ambiguity in Ebsteins and the role of CMR in accurate assessment and management.

RV in/out view showing the displaced tricuspid valve, atrialized and true RV
RVOT view from above showing a perpendicular view of the RVOT obstruction
RVOT view showing the area of supravalvar narrowing