Local impedance measurements during contact force‐guided cavotricuspid isthmus ablation for predicting an effective radiofrequency ablation

Abstract

Background An ablation catheter capable of contact force (CF) and local impedance (LI) monitoring (IntellaNav StablePoint, Boston Scientific) has been recently launched. We evaluated the relationship between the CF and LI values during radiofrequency catheter ablation (RFCA) along the cavotricuspid isthmus (CTI). Methods Fifty consecutive subjects who underwent a CTI‐RFCA using IntellaNav StablePoint catheters were retrospectively studied. The initial CF and LI at the start of the RF applications and mean CF and minimum LI during the RF applications were measured. The absolute and percentage LI drops were calculated as the difference between the initial and minimum LIs and 100 × absolute LI drop/initial LI, respectively. Results We analyzed 602 first‐pass RF applications. A weak correlation was observed between the initial CF and LI (r = 0.13) and between the mean CF and LI drops (r = 0.22). The initial LI and absolute and percentage LI drops were greater at effective ablation sites than ineffective ablation sites (median, 151 vs. 138 Ω, 22 vs. 14 Ω, and 14.4% vs. 9.9%; p < .001), but the initial and mean CF did not differ. At optimal cutoffs of 21 Ω and 10.8% for the absolute and percentage LI drops according to the receiver‐operating characteristic analysis, the sensitivity, and specificity for predicting an effective ablation were 57.4% and 88.9% and 80.0%, and 61.1%, respectively. Conclusions The effective sites during the CF‐guided CTI‐RFCA had greater initial LI and LI drops than the ineffective sites. Absolute and percentage LI drops of 21 Ω and 10.8% may be appropriate targets for an effective ablation.

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

“…However, the amount of >700 analyzed RFC applications allowed to evaluate CF and LI dynamics. Second, as heterogenous regions of healthy and impaired myocardium were targeted during ablation, target ∆LI may vary from levels proposed in previous experimental and clinical studies investigating index procedures ( Garrott et al, 2020 ; Szegedi et al, 2021 ; Ikenouchi et al, 2022 ; Sasaki et al, 2022 ) depending on local myocardial thickness, regional anatomical structures such as pouches and vessels as well as degree of fibrosis. Lastly, as follow-up data were not yet available, the impact of combined CF and LI assessment on long-term arrhythmia outcomes during repeat AF/AT ablation needs to be determined in future studies.…”

“…To account for inter-patient variability of blood pool LI, the difference between baseline tissue LI and blood pool LI (∆baseline LI) was measured in all patients. Sufficient lesion formation was defined as a ∆LI > 20 Ω according to previous preclinical findings ( Garrott et al, 2020 ; Szegedi et al, 2021 ; Ikenouchi et al, 2022 ; Sasaki et al, 2022 ). CF and LI dynamics were further analyzed considering local bipolar voltage for each RFC application, differentiating between high (>0.5 mV), intermediate (0.1–0.5 mV) and low (<0.1 mV) voltage ( Frontera et al, 2018 ).…”

“…Therefore, when compared to generator impedance, baseline LI shows greater variation between blood pool and tissue ( Sulkin et al, 2018 ; Gunawardene et al, 2019 ). A strong relationship between the LI drop during ablation (∆LI) and efficacy of lesion formation has been demonstrated ( Gunawardene et al, 2019 ; Garrott et al, 2020 ; Das et al, 2021 ; Solimene et al, 2021 ), with a ∆LI > 20 Ω being proposed to result in sufficient lesion formation according to previous clinical and experimental studies ( Garrott et al, 2020 ; Szegedi et al, 2021 ; Ikenouchi et al, 2022 ; Sasaki et al, 2022 ).…”

Local impedance and contact force guidance to predict successful cavotricuspid isthmus ablation with a zero-fluoroscopy approach

“…When this line was completed, the presence of BDB was assessed by counterclockwise and clockwise activation maps pacing from the proximal CS or the ablation catheter (positioned laterally to the CTI line) respectively. If BDB was present after this first ablation line and persisted after a waiting time of 30 min ( 18 ), first-pass conduction block was established ( 5 ), and all RF applications were considered successful. If BDB was not present after the first ablation line or we detected and early recovery in conduction across the CTI during the waiting time, an activation map along the CTI line was performed from the TA to the IVC to localize the gap.…”

“…In the past few years, a new ablation catheter (Intellanav MiFi OI™, Boston Scientific, Marlborough, U.S.A) capable of measuring real-time LI and LI drop while applying RF has been developed. LI drop results from tissue heating and constitutes a good predictor of lesion formation, catheter-tissue coupling, and effective ablation in different arrhythmic substrates, such as atrial fibrillation ( 3 ) and CTI-dependent atrial flutters ( 4 , 5 ). More recently, a new catheter with new technology and a different design (ie, without micro-electrodes) has been introduced (Intellanav StablePoint™, Boston Scientific, Marlborough, U.S.A), measuring not just LI drop but also assessing CF.…”