Pulmonary vein isolation in atrial fibrillation patients guided by a novel local impedance algorithm: 1-year outcome from the CHARISMA study

Background Highly localized impedance (LI) measurements during atrial fibrillation (AF) ablation have recently emerged as a viable real-time indicator of tissue characteristics and durability of the lesions created. We report the outcomes of acute and long-term clinical evaluation of the new DirectSense algorithm in AF ablation.Methods Consecutive patients undergoing AF ablation were included in the CHARISMA registry. RF delivery was guided by the DirectSense algorithm, which records the magnitude and time-course of the impedance drop. The ablation endpoint was pulmonary vein isolation (PVI), as assessed by the entrance and exit block.Results 3556 point-by-point first-pass RF applications of >10 s duration were analyzed in 153 patients (mean age=59 +/- 10 years, 70% men, 61% paroxysmal AF, 39% persistent AF). The mean baseline LI was 105 +/- 15 omega before ablation and 92 +/- 12 omega after ablation (p < .0001). Both absolute drops in LI and the time to LI drop (LI drop/tau) were greater at successful ablation sites (n = 3122, 88%) than at ineffective ablation sites (n = 434, 12%) (14 +/- 8 omega vs 6 +/- 4 omega, p < .0001 for LI; 0.73 [0.41-1.25] omega/s vs. 0.35[0.22-0.59 omega/s, p < .0001 for LI drop/tau). No major complications occurred during or after the procedures. All PVs had been successfully isolated. During a mean follow-up of 366 +/- 130 days, 18 patients (11.8%) suffered an AF/atrial tachycardia recurrence after the 90-day blanking period.Conclusion The magnitude and time-course of the LI drop during RF delivery were associated with effective lesion formation. This ablation strategy for PVI guided by LI technology proved safe and effective and resulted in a very low rate of AF recurrence over 1-year follow-up.