The use of highly localized impedance measurements to provide insight into tissue characteristics and their real-time evaluation seems to be helpful in order to precisely assess the electrical contact of the catheter and tip stability and to serve as a viable real-time indicator of tissue characteristics and durability of the lesions created [
5‐
7,
11]. Two commercially available catheters capable of recording LI are currently available. The IntellaNav MiFi OI catheter (Boston Scientific) generates LI measurements through mini-electrodes on the tip of the ablation catheter, the maximum value being reported within a three-dimensional mapping environment (Rhythmia; Boston Scientific). A recently released StablePoint catheter (Boston Scientific) incorporates CF-sensing capability in addition to LI [
8]. The ablation strategy for PV isolation guided by LI technology has proved safe and effective, resulting in a very low rate of AF recurrence over 1-year follow-up [
7]. However, as the dedicated ablation catheter (IntellaNAV Mifi OI, Boston Scientific) used in these studies was not able to collect data on CF sensing, it was not possible to compare CF and impedance measurements.
It is well recognized that, when RF energy is applied, CF is one of the variables, in addition to catheter stability, power output, temperature, and duration of RF output, that impacts on lesion size and transmurality [
4]. CF-guided RF catheter ablation has been associated with a significantly greater AF/atrial tachycardia-free survival benefit than non-CF-guided ablation in patients with paroxysmal AF rather than persistent AF. In addition, the CF-guided ablation strategy also reduced procedure time, fluoroscopy time, and RF time, though it had no distinct effect on the alleviation of procedure-related complications [
12]. Adding CF sensing to the LI-sensing technology has the potential to further increase the efficiency of LI-guided catheter ablation. Indeed, we found that CF significantly impacted on effective lesion formation during RF PV isolation. However, the benefit of higher than 25 g contact between the catheter and the tissue had less impact on the increase in LI drop. Our findings may have relevant implications in the clinical setting: [
1] good catheter-tissue contact improves the drop in LI and shortens the time needed to achieve it; [
2] the lack of benefit of a CF value of above 25 g might avoid excessive catheter pressure and potential complications. Similar data have already been reported with other CF-sensing technologies [
10,
13]; [
3] the CF value may help to differentiate the LI value of the blood pool from that of diseased tissue. Indeed, both the blood pool and diseased tissue display lower LI values than healthy tissue [
5,
14]. Of note, the magnitude of the mean LI drop observed in our study (23.0 ± 7 Ω) was significantly higher than that reported with previous LI technology (IntellaNAV Mifi OI, Boston Scientific) by other authors: Segreti et al. [
5], 14 ± 8 Ω; Das et al. [
6], 19.8 ± 11.1 Ω, and Solimene et al. [
7], 13 ± 8 Ω. To date, only one pilot study, which used the StablePoint™ ablation catheter [
15], showed that a local impedance drop > 21.8 Ω on the anterior wall and > 18.3 Ω on the posterior wall significantly increased the probability of creating a successful lesion. The CF-LI catheter does not have microelectrodes; instead, its distal tip serves as the return pole of the LI circuit. The larger electrical field created gives rise to CF-LI values that are typically 40–50% greater than those measured by the non-CF-LI catheter [
16]. Further studies will therefore be required in order to determine the magnitude of LI drop that predicts acute PV segment conduction block.