# Local multifrequency impedance changes after radiofrequency ablation in human atria: potential use for tissue characterization

## TL;DR

This study shows that measuring impedance at multiple frequencies can help distinguish between healthy and ablated heart tissue, potentially improving ablation procedures.

## Contribution

The study introduces local multifrequency impedance as a novel method to characterize tissue changes after radiofrequency ablation in human atria.

## Key findings

- Local multifrequency impedance (LMI) signatures differ significantly between pre-ablated, post-ablated, and blood pool tissue.
- LMI cyclic changes are inversely related to contact force and are more attenuated in post-ablated tissue.
- LMI can differentiate pre- from post-ablated tissue, offering potential clinical utility for monitoring ablation lesions.

## Abstract

Local impedance (LI) mapping provides additional tissue characterization of the atria substrate. Measuring LI at different current frequencies has the advantage of exploring intra- and extra-cellular compartments and may add useful information about tissue integrity. The objective of this study was to characterize the changes in local multifrequency impedance (LMI) after radiofrequency ablation in human atrial tissue.

In fifteen patients undergoing catheter ablation of atrial arrhythmias, we constructed a baseline high-density electroanatomical map (EAM) and measured the LMI (1–1,000 kHz) at fifty sites around the cava veins using the QDOT or Smarttouch electrocatheter. Then a point-by-point pulmonary vein isolation procedure was performed using radiofrequency energy in a temperature controlled mode (90W for 4 s for QDOT/30W for 30 s for Smarttouch). After confirming the PVI fifty additional LMI recordings per patient were performed around the initial sites. We performed an offline analysis to compare the values of bipolar voltage and LMI of blood, pre- and post-ablated tissue. We also analyzed the cardiac cycle changes of LMI and the effects of catheter orientation to the LMI, contact force and bipolar voltage.

A total of 641 pre-ablated and 190 post-ablated sites were studied from all patients. Blood pool, healthy and post-ablated myocardium presented distinctive LMI signatures (ZPRE = 110 ± 15 Ω vs. ZPOST = 90 ± 10 Ω vs. ZBLOOD = 90 ± 8 Ω; p < 0.001). LMI cyclic changes showed an inverse relationship with the contact force, and these were more attenuated in the post-ablated tissue (p < 0.001).

LMI can differentiate pre- from post-ablated tissue in a cohort of patients submitted to RF ablations. This new tool could be of potential clinical applicability for the characterization of the atrial substrate and to monitor lesion quality to perform durable ablation lesions.

NCT05159180 (https://www.clinicaltrials.gov); Unique Protocol ID: IIBSP-IMS-2021-74.