Concomitant real-time measurement and correlation of contact force to baseline local impedance and local impedance drops in RF ablation of left and right atrial procedures
Authors: Riesinger L , Siebermair J , Kochhaeuser S , Pesch E , Popal S R , Rassaf T , Wakili R 
Published: October 2021

Abstract

Introduction
Radiofrequency (RF) ablation is performed in various arrhythmias. Still, arrhythmia recurrence is a challenging problem, not only in atrial fibrillation (AF). One reason for arrhythmia recurrence is suspected to be due to remaining gaps. Measurement of local impedance (LI) and change of LI during RF application can be used as a predictor and surrogate for successful ablation. Another tool, used for the last couple of years, estimating sufficient tissue contact is provided by catheters with real-time contact force (CF) measurement. The new INTELLANAV STABLEPOINT™ catheter by Boston Scientific was recently introduced combing both strategies. We sought to investigate the parallel measurement and correlation of LI and CF in real-time during left atrial (LA) and right atrial (RA) procedures.

Methods
We included the first n=20 patients who underwent LA ablation for AF or atypical atrial flutter and n=7 patients who underwent RA procedures for atrial flutter or atrial tachycardia and analysed retrospectively procedural data. For every RF delivery RF duration, CF, baseline LI, minimal LI, LI drop, as well as minimal LI and LI drop after 5 and 10 sec was documented. Only RF deliveries with stable contact (ablation without delay) were included. We then correlated baseline LI to LI drop (maximum, after 5 sec, after 10 sec) and to the documented CF at baseline.

Results
A total of 27 procedures was analysed. In total, 777 RF deliveries (663 in LA, 114 in RA) were documented with a mean RF duration of 21.7 sec. Mean baseline LI was 148.4 Ω, minimal LI 130.6Ω, LI after 5 sec 135.0 Ω and LI after 10sec 132.5 Ω. Mean complete LI drop was 17.8 Ω (13.4 Ω after 5 sec, 15.8 Ω after 10 sec). Mean CF was 15.5g. We could see a significant positive correlation between average CF and LI drop (p&lt;0.01) (figure 1A), as well as between average CF and LI drop after 5 sec (p&lt;0.01) and after 10 sec (p&lt;0.01). Also, for baseline LI we could see a significant strong positive correlation to LI drop (p&lt;0.001) (figure 1B), LI drop after 5 sec (p&lt;0.001) and after 10 sec (p&lt;0.001). Baseline LI did not correlate to average CF. Baseline LI was significantly higher in RA, when compared to LA (152.5Ω vs. 147.7Ω; p&lt;0.05). LI drop did not differ between RA and LA procedures (17.8Ω vs. 17.7Ω), whereas mean RF duration per RF application was significantly longer in LA compared to RA procedures (22.8sec vs. 15.3sec; p&lt;0.001) and applied CF was also higher in LA compared to RA procedures (16.0Ω vs. 12.8Ω; p&lt;0.001).

Conclusion
Parallel real-time measurement of LI and CF is providing further insights into ablation biophysics. Based on these results the CF values might provide a prediction of subsequent lesion formation. A combination with LI measurement seems to be useful to prevent insufficient lesions, predisposing to gap formation and associated with arrhythmia recurrence, but also to potentially guarantee a higher safety by visualizing the applied CF and consecutive LI drop.

Funding Acknowledgement
Type of funding sources: None. Figure 1