Preliminary Real-World Experience on Mitral Isthmus Ablation with a Novel Catheter That Toggles Between Radiofrequency and Pulsed Field Ablation

Abstract Background The mitral isthmus (MI) is frequently targeted during the ablation of persistent atrial fibrillation (AF). Nevertheless, achieving a complete bidirectional MI block using radiofrequency (RF) is often technically challenging and time-consuming1,2. Previously, we described a fluoroscopy-guided technique to achieve MI block using a penta-spline pulsed field ablation (PFA) catheter3. Recently, a new catheter was introduced, which toggles between RF and PFA and is integrated into a 3D mapping system, thus supposedly facilitating its use for the ablation of extra-pulmonary vein structures4. Purpose To describe the acute efficacy and procedural features of the first cases of posterior MI ablation performed with the toggling catheter at two centers. Methods We collected and reviewed demographic, clinical and procedural features of all patients who underwent ablation of the posterior MI at our centers between September and October 2023. Ablation of the MI was performed with either RF or PFA according to operator’s discretion. Bidirectional MI block was validated through activation mapping and differential pacing. Results During the study period, 44 patients were treated with the toggling catheter. Out of them, 16 patients (aged 68.3±10.1 years; 29% females) underwent posterior MI ablation for persistent AF, in addition to PVI and posterior wall isolation. Mean history of AF was 29.8±34.5 months and mean LA volume 135.6±54.9 ml. Skin-to-skin procedural time (93 minutes, IQR 64-112), LA mapping time (9.0 min, IQR 7.3-12.1) and time required for MI ablation (4.0 min, IQR 3.3-6.5) were remarkably short. In PFA-treated patients (10 cases), first-pass MI block was achieved in 8 (80%), with 16 (IQR 12-22) applications; none of these patients required RF touch-up. In the remaining 6 RF-treated patients, first-pass MI block was achieved in 3 (50%) patients with 8 (IQR 6-13) applications. Additional PFA applications (median 3, IQR 2-5) on the most venous portion of the MI were required in all RF-treated patients. In the 5 patients in whom bidirectional block could not be achieved at first-pass, remapping and touch-up application time were 2.6 (IQR 2.6- 6.3) and 2.0 (IQR 0.8-5.2) minutes, respectively. Eventually, bidirectional MI block was achieved in 16/16 (100%) patients by the end of the procedure. Importantly, no patients in the entire cohort experienced complications such as coronary artery spasm or clinically significant pericardial effusion. Conclusions Several observations can be made on this first real-world experience on posterior MI ablation with the toggling catheter: first, acute safety and efficacy in achieving a bidirectional MI block are high with both PFA and RF; secondly, patients undergoing RF ablation often require additional PFA applications on the venous segment of the MI; lastly, the time required to achieve MI block is remarkably short even when remapping and touch-up applications are needed.Figure 1Figure 2