Improved Ablation Efficiency in PVI Guided by Contact Force and Local Impedance: Chronic Canine Model

Abstract

Background: The purpose of this study was to assess the effect local impedance (LI) has on an ablation workflow when combined with a contact force (CF) ablation catheter.Methods: Left pulmonary vein isolation was performed in an in vivo canine model (N = 8) using a nominal (30 W) or an elevated (50 W) power strategy with a CF catheter. The catheter was enabled to measure LI prior to and during ablation. LI was visible for only one of the vein isolations.Results: Chronic block was achieved in all animals when assessed 30 ± 5 days post-ablation procedure with a median LI drop during RF ranging from 23.0 to 34.0 Ω. In both power cohorts, the median radiofrequency (RF) duration decreased if LI was visible to the operator (30 W only CF: 17.0 s; 30 W CF + LI: 14.0 s, p = 0.009; 50 W only CF: 6.0 s; 50 W CF + LI: 4.0 s, p = 0.019). An inverse relationship between the LI prior to RF delivery and the RF duration required to achieve an effective lesion was observed. There was no correlation between the magnitude of the applied force and the drop in LI, once at least 5 g was achieved.Conclusions: An elevated power strategy with the context of CF and LI led to the most efficient titration of successful RF energy delivery. The combination of feedback allows for customization of the ablation strategy based on local tissue variation rather than a uniform approach that could potentially lead to overtreatment. Higher LI drops were more readily achievable when an elevated power strategy was utilized, especially in conditions where the catheter was coupled against tissue with low resistivity. Clinical study is warranted to determine if there is an additive safety benefit to visualizing the dynamics of the tissue response to RF energy with LI when an elevated power strategy is used.

Combined contact force and local impedance dynamics during repeat atrial fibrillation catheter ablation

“…Baseline LI showed the highest correlation to ΔLI which is in line with recently published experimental (Garrott et al, 2020;Gutbrod et al, 2022) and clinical studies (Martin et al, 2018;Gunawardene et al, 2019;Szegedi et al, 2021;Matsuura et al, 2022;Solimene et al, 2022). Furthermore, according to our results combined mean CF and baseline LI was the best predictor for a ΔLI > 20 Ω in comparison to applied mean CF or baseline LI alone.…”

“…Several experimental and clinical studies have recently been published reporting experiences of combined CF and LI assessment during index AF ablation (Szegedi et al, 2021;Gutbrod et al, 2022;Solimene et al, 2022;Yasumoto et al, Frontiers in Physiology frontiersin.org 2022). Single-shot devices have seen increased usage for index AF ablations in recent years (Mulder et al, 2021).…”

Characteristics of Very High-Power, Short-Duration Radiofrequency Applications

“…Gutbrod et al ( 13 ) showed that the local impedance of the tissue is significantly higher when CF is at least 5 g compared to those with an applied CF below 5 g. However, when comparing different CF values above 5 g, they found no significant difference in local impedance. This suggests that once CF reaches a value of 5 g, stable contact with the tissue is achieved, and a further increase in CF does not result in significantly greater stability ( 13 ). Consistent with this, we also found that a CF ≥ 5 g results in significantly higher maximum temperatures during ablation ( Figure 5 ).…”

“…However, it was clearly showed recently that changes in generator impedance show a weak correlation with lesion formation (26). Gutbrod et al (13) showed that the local impedance of the tissue is significantly higher when CF is at least 5 g compared to those with an applied CF below 5 g. However, when comparing different CF values above 5 g, they found no significant difference in local impedance. This suggests that once CF reaches a value of 5 g, stable contact with the tissue is achieved, and a further increase in CF does not result in significantly greater stability (13).…”

“…Therefore, several predictors of AF recurrence have been described, such as hypertension, left atrial enlargement, and certain anatomical variations of pulmonary veins (PVs) and the left atrial ridge (5)(6)(7)(8). In addition, numerous technological innovations in catheter ablation are also being sought to reduce recurrence, including the CLOSE protocol and the measurement of local impedance (9)(10)(11)(12)(13)(14). Still, AF recurrence remained a critical issue (15,16).…”