Patient-tailored low-voltage-guided ablation of atrial fibrillation: initial experience using a novel ultra-low-temperature cryoablation system

Abstract

Abstract Introduction The ideal ablation strategy for patients (pts) with persistent atrial fibrillation (PersAF) is still debated. In recent randomized studies, strategies of ablating electrically abnormal atrial regions in addition to pulmonary vein isolation (PVI) have shown promise, and a novel ultra-low-temperature cryoablation (ULTC) system might overcome the limitations of radiofrequency (RF) energy to create transmural lesions in diseased tissue. Purpose Aim of this study is to report procedural aspects, acute efficacy, and safety of our initial experience in treating AF pts with this novel ULTC system. Methods Patients scheduled for catheter ablation who had a high likelihood of having left atrial (LA) low voltage zones (LVZ) underwent ablation with the ULTC system. A detailed high-density LA 3D-electronatomical map was created in sinus rhythm using a multi-electrode catheter. Bipolar LVZs were defined as at least 1cm2 surface of bipolar voltage <0.5mV. The ablation strategy consisted of PVI and linear ablation of the LVZs, transecting (if narrow) or isolating (if broad) the areas of abnormal signals and anchoring these lines to electrically silent structures (PVs or mitral valve ring). Electrical isolation and block across linear ablations were tested as universally accepted. Continuous variables are expressed as median (and interquartile ranges). Results From April to September 2023, 25 pts (10 female) were included (see table for patients´ and procedural characteristics). Procedure duration was 210 (135-270) min, and diminished over time from initially (in the first 12 pts) 260 (203.75-302.50) min to 190 (135-235) min (p=0.047). PVI was achieved in 15/18 pts (83%) using the ULTC, in the remaining 3 pts RF energy touch-up was needed. Linear ablation and isolation of LVZs were always (41/41 in 22pts, 100%) successfully achieved with the ULTC (see figure for an example). Except for 1 right phrenic nerve palsy, no major acute complications were observed. Post-procedural chest pain was not reported by any patient, in 1 patient mild pericardial effusion was detected and treated conservatively. During the 48h post-procedural ECG-monitoring, no sustained atrial arrhythmias occurred. Conclusions This is the first report of patient-tailored low-voltage-guided AF-ablation using a novel ULTC system. Despite representing our initial clinical experience, acute efficacy was very good (95% of acute bidirectional block across lines). Procedure-duration decreased over time, indicating an initial learning curve. Acute safety was reassuring but particular attention should be paid for phrenic nerve function during ablation of the right PVs. The absence of post-procedural pain, pericardial effusion, or acute post-procedural arrhythmias indicates limited ablation-induced inflammation.Result of ULTC ablation in a diseased LA