Asian Journal of Cardiology Research

Background: Ebstein’s anomaly is frequently associated with complex arrhythmogenic substrates, particularly multiple accessory pathways and concealed intrinsic conduction abnormalities. However, preservation of native right-sided conduction following successful accessory pathway ablation remains exceptionally uncommon and sparsely reported in literature.

Aims: To report a unique case of Ebstein's Anomaly (EA) where successful radiofrequency catheter ablation of two accessory pathways revealed a remarkably preserved native conduction system, and to discuss the role of thyrotoxicosis as a metabolic trigger in destabilizing congenital substrates leading to acute symptomatic presentation.

Case Presentation: A 13-year-old female with underlying EA and Wolff-Parkinson-White syndrome (baseline QRS 170 ms) presented with palpitations exacerbated by thyrotoxicosis. EPS and 3D mapping identified two distinct right-sided bypass tracts. Following successful radiofrequency ablation (RFA) utilizing an irrigated catheter (25 Watts, temperature – limited for 45 seconds), the post-procedural ECG revealed a narrow QRS of 78 ms with a striking absence of the expected right bundle branch block (RBBB).

Discussion: EA is classically coupled with severe intrinsic right-sided conduction system disease. This case challenges the "universal" RBBB paradigm. Thyrotoxicosis served as a metabolic "second hit," increasing myocardial excitability and triggering symptomatic tachycardia. 

Conclusion: Conduction system disease in EA displays remarkable clinical heterogeneity. Clinicians must remain vigilant for extracardiac metabolic triggers when a previously stable arrhythmic substrate becomes acute, and long-term surveillance is necessary given the high recurrence risk associated with remodelled tricuspid rings.