Objective: Unknown etiology Background: Radiofrequency ablation in cases of Wolff-Parkinson-White (WPW) syndrome is a relatively safe procedure that yields good results. However, the electrical characteristics of WPW syndrome have not yet been fully elucidat-ed. Herein, we report 2 cases of WPW syndrome, wherein antegrade conduction was abolished first, followed by retrograde conduction. Case Reports: Case 1: A 15-year-old boy who recently reported experiencing frequent palpitations was diagnosed with type A WPW syndrome by electrocardiography (ECG). Radiofrequency energy was delivered to the earliest activa-tion site using an ablation catheter. This procedure abolished antegrade accessory pathway conduction in 6 seconds, and then the ablation was continued for 60 seconds; however, retrograde accessory pathway con-duction remained intact. Hence, radiofrequency ablation was performed to further deliver radiofrequency en-ergy to abolish the retrograde accessory pathway conduction. Case 2: A 19-year-old woman with palpitations since elementary school was diagnosed with type A WPW syn-drome by ECG. Radiofrequency energy was delivered to the earliest activation site through an ablation cathe-ter to abolish antegrade accessory pathway conduction in approximately 1 second, and then the ablation was continued for 60 seconds. Retrograde accessory pathway conduction was preserved, and further radiofrequen-cy ablation performed multiple times in the same vicinity abolished retrograde accessory pathway conduction. Conclusions: We managed 2 cases of WPW syndrome wherein antegrade and retrograde accessory pathway conduction were individually abolished. This phenomenon may have been caused by an incomplete lesion that resulted in a functional block.
