Surpassing the complex substrate of accessory pathways ablation in ebstein anomaly

Abstract Funding Acknowledgements Type of funding sources: None. Background and Aims Data regarding long-term follow-up of radiofrequency catheter ablation (RFCA) of accessory pathways (APs) in patients (P) with Ebstein's anomaly are limited. This type of procedure is considered challenging due to multiple and broad APs. The present study aimed to describe the electrophysiological features of APs in P with Ebstein's anomaly, and report our RFCA experience with an open-window electroanatomic 3D mapping using high-density mapping catheters in these patients. Methods and results A retrospective study of 15 consecutive Ebstein anomaly P with APs who underwent an electrophysiologic study and RFCA from 2013 to 2022. There were a total of 21 manifested non-decremental APs. APs were mainly located on the posterior, posteroseptal, and posterolateral tricuspid annulus. The index procedure was unsuccessful in six P, with the need for a redo procedure. This redo procedure was performed with a high-density catheter (Pentaray, Biosense or HD-Grid, Abbott), using the open-window annotation algorithm (Abbott's NavX Precision or BiosenseWebster Carto3), guided by CT integration and intracardiac echo. Broad APs were documented in all these six patients (width range 2-15cm) and successfully ablated. In one P, the AP encompassed ¾ of the TA, resulting in a complete AV block after the procedure, having fitted a pacemaker. All P remained free from tachycardias during 15±8 months of follow-up, with the majority (n=12) having sinus rhythm with morphology of right bundle branch block, while three patients showed a narrow QRS. Conclusions RFCA in P with Ebstein anomaly is challenging, but safe, and has a high long-term success rate. APs are predominantly right-sided, manifest and localized to the lower half of the anatomic tricuspid annulus. Some APs have broad widths. In this population, the new high-resolution mapping catheters, using the open-window annotation, produce an improved anatomical resolution of the APs, increasing the odds of success.