Impact of a formula combining local impedance and conventional parameters on lesion size prediction

Introduction Radiofrequency catheter ablation is a cornerstone of treatment for many cardiac arrhythmias. Progression in three‐dimensional mapping and contact‐force sensing technologies have improved our capability to achieve success, but challenges still remain. Methods In this article, we discuss the importance of overall circuit impedance in radiofrequency lesion formation. This is followed by a review of the literature regarding recently developed “local impedance” technology and its current and future potential applications and limitations, in the context of established surrogate markers currently used to infer effective ablation. Results We discuss the role of local impedance in assessing myocardial substrate, as well as its role in clinical studies of ablation. We also discuss safety considerations, limitations and ongoing research. Conclusion Local impedance is a novel tool which has the potential to tailor ablation in a manner distinct from other established metrics.

Section: Li-opportunities and Limitationsmentioning

confidence: 99%

Local impedance for the optimization of radiofrequency lesion delivery: A review of bench and clinical data

Chu

Calvert

Futyma

et al. 2021

“…All measurements were taken using digital vernier calipers by the same investigator who was blinded to the ablation parameters of the lesion. Lesion surface area and lesion volume were calculated from the following formulae 15–17 ;

\text{Lesion}\,\text{surface}\,\text{area}\,=\pi \times {\rm{a}}/2\times {\rm{b}}/2.

\text{Lesion}\,\text{volume}\,=(1/6)\times \pi \times ({{\rm{c}}}^{2}\times {\rm{d}}+{\rm{e}}\times {{\rm{a}}}^{2}/2).

…”

Section: Methodsmentioning

confidence: 99%

Section: Lesion Measurementsmentioning

confidence: 99%

“…Longer-duration and higher-power RF applications have been reported to be risk factors for steam-pops, 17 and some studies have demonstrated an association between higher CF and steam-pops. 17,20,22 However, to the best of our knowledge, this is the first study comparing the lesion characteristics and risk of steam-pops between TFC-ablation and PC-ablation, targeting the fixed AI. Interestingly, the present study demonstrated a strong link between lower CF and steam-pops in both catheters, contrary to previous reports.…”

Section: Risk Factors For Steam-popsmentioning

confidence: 99%

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Comparison of lesion characteristics using temperature‐flow‐controlled versus conventional power‐controlled ablation with fixed ablation index

Ikenouchi

Takigawa

Goya

et al. 2023

Self Cite

Introduction The QDOT‐MicroTM catheter is a novel irrigated contact force (CF) sensing catheter which benefits from thermocouples for temperature monitoring, allowing temperature‐flow‐controlled (TFC) ablation. We compared lesion metrics at fixed ablation index (AI) value during TFC‐ablation and conventional power‐controlled (PC)‐ablation. Methods A total of 480 RF‐applications were performed on ex‐vivo swine myocardium with predefined AI targets (400/550) or until steam‐pop occurred, using the QDOT‐MicroTM (TFC‐ablation) and Thermocool SmartTouch SFTM (PC‐ablation). Results Both TFC‐ablation and PC‐ablation produced similar lesions in volume (218 ± 116 vs. 212 ± 107 mm3, p = .65); however, lesions using TFC‐ablation were larger in surface area (41.3 ± 8.8 vs. 34.8 ± 8.0 mm2, p < .001) and shallower in depth (4.0 ± 1.0 vs. 4.2 ± 1.1 mm, p = .044). Average power tended to be lower in TFC‐alation (34.2 ± 8.6 vs. 36.9 ± 9.2, p = .005) compared to PC‐ablation due to automatic regulation of temperature and irrigation‐flow. Although steam‐pops were less frequent in TFC‐ablation (24% vs. 15%, p = .021), they were particularly observed in low‐CF (10 g) and high‐power ablation (50 W) in both PC‐ablation (n = 24/240, 10.0%) and TFC‐ablation (n = 23/240, 9.6%). Multivariate analysis revealed that high‐power, low‐CF, long application time, perpendicular catheter orientation, and PC‐ablation were risk factors for steam‐pops. Furthermore, activation of automatic regulation of temperature and irrigation‐flow was independently associated with high‐CF and long application time while ablation power had no significant relationship. Conclusions With a fixed target AI, TFC‐ablation reduced the risk of steam‐pops, producing similar lesions in volume, but with different metrics in this ex‐vivo study. However, lower CF and higher power in fixed‐AI ablation may increase the risk of steam‐pops.

“…It is generally believed that irrigation catheters are more suitable than nonirrigation catheters to create deeper lesions, but this is based on the capability of irrigation catheters to deliver large RF energy without excessive catheter temperature rise and/or thrombus formation, and so on. [10][11][12] Indeed, in our nominal application time ablation, the 40-s application using nonirrigation catheter was completed only in 8/12 applications due to excessive temperature rise (Group 4), but all 12 were successfully accomplished by use of irrigation catheter (Group 2).…”

Section: Rf Application Modes and Created Lesionsmentioning

confidence: 96%

Distribution of excitation recoverable myocardium after radiofrequency ablation and its relation to energy application time and irrigation

Saitoh

Kasai

Fuse

et al. 2023

Introduction Radiofrequency (RF) catheter ablation induces excitation recoverable myocardium around durable core lesions, and its distribution may be different depending on energy delivery methods. Methods and Results In coronary perfusing porcine hearts, pacing threshold through the ventricle was measured using eight‐pole (1‐mm distance) needle electrodes vertically inserted into myocardium before, within 3 min after and 40 min after 40 W ablation with 10‐g catheter contact (Group 1: irrigation catheter for 15 s, Group 2: irrigation catheter for 40 s, Group 3: nonirrigation catheter for 15 s, Group 4: nonirrigation catheter for 40 s). Ablation was accomplished in all 12 ablations in Groups 1–3 whereas in 8/12 ablations in Group 4 because of high‐temperature rise. Within 3 min after ablation, 10.0 V pacing uncaptured electrodes were distributed from the surface to inside the myocardium, and its depth was deeper in 40 s than in 15 s ablation. 40 min after ablation, excitation recovery at one or more electrodes below the durable lesion was observed in all Groups. Excitation recovery electrodes were also observed on the surface in Group 1 but not the other Groups. Accordingly, the number of excitation‐recovered electrodes were larger in Group 1 than the other Groups. Conclusions Regardless of the ablation methods, excitation recoverable myocardium was present around 1.0 mm below the durable lesions. Lesions created by short application time using an irrigation catheter may have included large excitation recoverable myocardium soon after ablation because of the presence of reversible myocardium on well‐irrigated myocardial surfaces.