Successful Cryoablation for Parahissian Right Midseptal Accessory Pathway with Atrioventricular Block during Radiofrequency Ablation

Abstract

A 58-year-old-male received radiofrequency catheter ablation（RFCA）for symptomatic manifest WPW syndrome. The morphology of delta wave showed negative / QS pattern in the lead V₁, suggesting septal accessory pathway. Both antegrade and retrograde conduction of the accessory pathway demonstrated the earliest activation at the right mid-septum near the His bundle. Although the accessory pathway disappeared immediately after careful RFCA at this site, temporally atrioventricular block occurred. The accessory pathway recurred after discontinuing the RFCA. The cryoablation was performed in the second ablation session. The accessory pathway was eliminated radically without any atrioventricular conduction disturbance by cryoablation at the same position（the right parahissian mid-septum）as in the first ablation session.