Dynamic Pre-Excitation and Sequential Ablation of Three Distinct Right-Sided Accessory Pathway Sites in a Child with Wolff–Parkinson–White Syndrome: A Case Report

Background: Multiple accessory pathways are uncommon in pediatric Wolff–Parkinson–White syndrome and may cause dynamic changes in ventricular pre-excitation, complicating electrocardiographic localization. Case presentation: A 7-year-old girl with recurrent palpitations and syncope exhibited variable QRS morphology and delta-wave patterns. Electrophysiological findings were consistent with orthodromic atrioventricular reentrant tachycardia. Sequential CARTO mapping identified three spatially separated right-sided accessory pathway sites. Ablation of AP1 (7 o’clock, tricuspid annulus) and AP2 (11 o’clock, tricuspid annulus) produced successive QRS morphological changes without eliminating pre-excitation. AP3 was localized just superior to the coronary sinus ostium at approximately the 4 o’clock position, where ablation eliminated pre-excitation. No tachycardia was inducible immediately afterward. However, pre-excitation reappeared on ECG at 1-month follow-up and persisted at 3 months, with two patient-reported tachycardia episodes but no recurrent syncope. Conclusions: Dynamic pre-excitation patterns may suggest multiple accessory pathways. Sequential mapping and electrocardiographic reassessment can help identify residual pathway conduction, although acute procedural success does not ensure sustained elimination of pre-excitation.