Local impedance drop guided versus lesion size index guided pulmonary vein isolation: long-term outcomes and chronic reconnections
Authors: Lyan E , Pantlik R , Maslova V , Frank D , Demming T 
Published: May 2023

Abstract

Funding Acknowledgements
Type of funding sources: None.

Introduction
Insufficient lesion depth and discontinuity of lesion lines are reasons for reconnections after point-by-point radiofrequent pulmonary vein isolation (PVI). Different technologies have shown to be useful for prediction of effective lesions. Measurement of the magnitude of local tissue impedance drop (LID) and calculation of lesion size index (LSI) based on monitoring of contact force are examples for corresponding technologies.

Purpose
To compare the long-term outcomes of LID guided with LSI guided PVI.

Methods
In this retrospective study we compared two groups of patients who underwent point-by-point radiofrequency PVI for treatment of atrial fibrillation. In the LID-guided group (n=35) energy was delivered using an ablation catheter with local impedance monitoring. Ablation was terminated when LID reached a plateau (Fig. A). In the LSI-guided group (n=31) lesions were created using an ablation catheter with contact force monitoring until the target LSI was reached in each point (LSI=5 for anterior and LSI=4 for posterior segments, respectively, Fig B). The inter-lesion distance of &lt;6 mm with power of 40 W for anterior and 30W for posterior segments was used in both groups. A gap-map and touch-up ablation was performed along the index ablation line if the first pass PVI did not occur, or in the case of an acute reconnection after 20 min of waiting time. In the long-term follow-up, a holter ECG was scheduled 3, 6 and 12 months after the initial ablation as well as symptom-driven visits with ECG registration. In case of symptomatic arrhythmia recurrence, a second procedure was performed including validation of PVI, mapping of reconnection site and RePVI, if necessary.

Results
All pulmonary veins were successfully isolated by encirclement of ipsilateral veins during initial procedure. During the 11.5±2.9 months follow-up, 12 out of 35 (34.3%) patients from LID-guided group and 5 out of 31 (16.1%) patients from LSI-guided group experienced arrhythmia recurrence. Kaplan-Meier survival analysis showed statistically significant higher probability of the arrhythmia recurrence in patients treated with LID-guided approach (log-rank=4.37, p=0.037, Fig C). Redo procedure was performed for 10 (28.6%) patients in LID-guided group and 3 (9.7%) patients in LSI-guided group and chronic pulmonary vein reconnections were detected in 7 out of 10 (70%) and 2 out of 3 (67%) patients, respectively (Fig D).

Conclusions
Despite initial successful isolation of all pulmonary veins, LID-guided ablation resulted in significantly higher probability of arrhythmia recurrence during the long-term follow-up as well as higher rate of chronic PV reconnections (although not statistically significant) as compared to LSI-guided ablation. This reflects the nature of contact force guided ablation anticipating the quality of catheter-tissue interface before each application, which is not possible with an impedance only guided approach.