Introduction
Recently, a novel technology able to measure local impedance (LI) and tissue characteristics has been made available for clinical use. This analysis explores the relationships among LI and generator impedance (GI) parameters in atrial fibrillation (AF) patients. Characterization of LI among different ablation spots and procedural success were also evaluated.
Methods and Results
Consecutive patients undergoing AF ablation from the CHARISMA registry at five Italian centers were included. A novel radiofrequency (RF) ablation catheter with a dedicated algorithm (DIRECTSENSE™) was used to measure LI and to guide ablation. The ablation endpoint was pulmonary vein (PV) isolation. We analyzed 2219 ablation spots created around PVs in 46 patients for AF ablation. The mean baseline tissue impedance was 105.8 ± 14 Ω for LI versus 91.8 ± 10 Ω for GI (p < .0001). Baseline impedance was homogenous across the PV sites and proved higher in high‐voltage areas than in intermediate‐ and low‐voltage areas and the blood pool (p < .001). Both LI and GI displayed a significant drop after RF delivery, and absolute LI drop values were significantly larger than GI drop values (14 ± 8 vs. 3.7 ± 5 Ω, p < .0001). Every 5‐point increment in LI drop was associated with successful ablation (odds ratio = 3.05, 95% confidence interval: 2.3–4.1, p < .0001). Conversely, GI drops were not significantly different comparing successful versus unsuccessful sites (3.7 ± 5 vs. 2.8 ± 4 Ω, p = .1099). No steam pops or major complications occurred during or after the procedures. By the end of the procedures, all PVs had been successfully isolated in all patients.
Conclusions
The magnitude of the LI drop was more closely associated with effective lesion formation than the GI drop.
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 Ω before ablation and 92 ± 12 Ω after ablation (p < .0001). Both absolute drops in LI and the time to LI drop (LI drop/τ) were greater at successful ablation sites (n = 3122, 88%) than at ineffective ablation sites (n = 434, 12%) (14 ± 8 Ω vs 6 ± 4 Ω, p < .0001 for LI; 0.73 [0.41–1.25] Ω/s vs. 0.35[0.22–0.59 Ω/s, p < .0001 for LI drop/τ). 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.
Physical activity (PA) is a cornerstone of prevention to decrease mortality in patients with chronic cardiovascular disease, including heart failure. 1,2 Implantable cardiac devices offer the opportunity to monitor PA and data derived from implantable devices have been associated with shortand long-term outcomes. 3,4 During the severe acute respiratory syndrome coronavirus 2 pandemic, restrictions to outdoor activity were imposed by national authorities. In Italy, after the first case of coronavirus disease-2019 (COVID-19) on February 21, the so-called lockdown act was passed on March 8, 2020. 5 These rigorous measures decreased the impact of COVID-19 pandemic on the National Health System, 6 but likely resulted in changes in the ability of patients to maintain PA levels. In the current study, we examined the impact of the COVID-19 and regulatory movement restrictions on the PA of patients with an implantable cardioverter defibrillator.
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