Ultra-high-density mapping of epicardial to endocardial breakthrough after previous successful cavotricuspid isthmus ablation
S S Bun, P Taghji, D Scarlatti, J Taieb, E Ferrari, F SquaraAbstract
Introduction
Recurrences are rare after successful cavotricuspid isthmus (CTI) ablation. These recurrences may be related to remaining endocardial gaps along the initial ablation line, or to epicardial to endocardial breakthroughs (EEB) in the presence of complete endocardial line of block. We aimed to investigate the electrophysiological characteristics of EEB-related CTI-dependent AFL, using ultra-high-density (UHD) mapping, after a previous successful ablation.
Methods
Six patients with EEB-related CTI-dependent AFL were identified at two institutions. All presented a previous successful conventional CTI ablation. UHD activation maps and ablation procedure were analyzed.
Results
From Jan 2021 to Jan 2025, a total of seven EEBs were identified in six patients (53 ± 14 y, male 66 %) with confirmation of endocardial conduction block within the CTI using UHD mapping. Four EEBs (including three at the right atrial [RA] septum and one in inferolateral RA) were recorded during tachycardia (mean cycle length 240 ± 40 ms; mean mapping time 5.3 ± 1.1 min ; mean number of electrograms 10718 ± 10030). The other three EEBs were identified at the inferolateral RA during pacing from the coronary sinus. Three patients underwent RF delivery at the RA septum (without tachycardia interruption), while ablation targeted at the inferolateral RA EEB was performed in all cases (Picture 1). In one patient, complete endo-epicardial block was achieved by ethanol infusion within a posterior RA vein (Picture 2). Mean transisthmus time was measured at 162 ± 59 ms at the end of the procedure. Total procedure and fluoroscopy time were respectively 120 ± 7 min and 6 ± 5 min. No recurrences were recorded after a mean follow-up of 18 ± 12 months.
Conclusion
The largest series of EEB-related CTI-dependent AFL is described, after an initial successful procedure. These challenging situations may advocate for systematic use of UHD mapping in case of repeated CTI ablation.Inferolateral epicardial connectionright atrial vein ethanol infusion