Pulmonary vein isolation in atrial fibrillation patients guided by a novel local impedance algorithm: 1-year outcome from the CHARISMA study

2024 European Heart Rhythm Association/Heart Rhythm Society/Asia Pacific Heart Rhythm Society/Latin American Heart Rhythm Society expert consensus statement on catheter and surgical ablation of atrial fibrillation

In the last three decades, ablation of atrial fibrillation (AF) has become an evidence-based safe and efficacious treatment for managing the most common cardiac arrhythmia. In 2007, the first joint expert consensus document was issued, guiding healthcare professionals involved in catheter or surgical AF ablation. Mounting research evidence and technological advances have resulted in a rapidly changing landscape in the field of catheter and surgical AF ablation, thus stressing the need for regularly updated versions of this partnership which were issued in 2012 and 2017. Seven years after the last consensus, an updated document was considered necessary to define a contemporary framework for selection and management of patients considered for or undergoing catheter or surgical AF ablation. This consensus is a joint effort from collaborating cardiac electrophysiology societies, namely the European Heart Rhythm Association, the Heart Rhythm Society (HRS), the Asia Pacific HRS, and the Latin American HRS.

Catheter-tissue contact optimizes pulsed electric field ablation with a large area focal catheter

INTRODUCTION

Pulsed electric field (PEF) ablation relies on the intersection of a critical voltage gradient with tissue to cause cell death. Field-based lesion formation with PEF technologies may still depend on catheter-tissue contact (CTC). The purpose of this study was to assess the impact of CTC on PEF lesion formation with an investigational large area focal (LAF) catheter in a preclinical model.

METHODS

PEF ablation via a 10-spline LAF catheter was used to create discrete right ventricle (RV) lesions and atrial lesion sets in 10 swine (eight acute, two chronic). Local impedance (LI) was used to assess CTC. Lesions were assigned to three cohorts using LI above baseline: no tissue contact (NTC: ≤∆10 Ω, close proximity to tissue), low tissue contact (LTC: ∆11-29 Ω), and high tissue contact (HTC: ≥∆30 Ω). Acute animals were infused with triphenyl tetrazolium chloride (TTC) and killed ≥2 h post-treatment. Chronic animals were remapped 30 days post-index procedure and stained with infused TTC.

RESULTS

Mean (± SD) RV treatment sizes between LTC (n = 14) and HTC (n = 17) lesions were not significantly different (depth: 5.65 ± 1.96 vs. 5.68 ± 2.05 mm, p = .999; width: 15.68 ± 5.22 vs. 16.98 ± 4.45 mm, p = .737), while mean treatment size for NTC lesions (n = 6) was significantly smaller (1.67 ± 1.16 mm depth, 5.97 ± 4.48 mm width, p < .05). For atrial lesion sets, acute and chronic conduction block were achieved with both LTC (N = 7) and HTC (N = 6), and NTC resulted in gaps.

CONCLUSIONS

PEF ablation with a specialized LAF catheter in a swine model is dependent on CTC. LI as an indicator of CTC may aid in the creation of consistent transmural lesions in PEF ablation.

2024 European Heart Rhythm Association/Heart Rhythm Society/Asia Pacific Heart Rhythm Society/Latin American Heart Rhythm Society expert consensus statement on catheter and surgical ablation of atrial fibrillation

In the last three decades, ablation of atrial fibrillation (AF) has become an evidence-based safe and efficacious treatment for managing the most common cardiac arrhythmia. In 2007, the first joint expert consensus document was issued, guiding healthcare professionals involved in catheter or surgical AF ablation. Mounting research evidence and technological advances have resulted in a rapidly changing landscape in the field of catheter and surgical AF ablation, thus stressing the need for regularly updated versions of this partnership which were issued in 2012 and 2017. Seven years after the last consensus, an updated document was considered necessary to define a contemporary framework for selection and management of patients considered for or undergoing catheter or surgical AF ablation. This consensus is a joint effort from collaborating cardiac electrophysiology societies, namely the European Heart Rhythm Association, the Heart Rhythm Society, the Asia Pacific Heart Rhythm Society, and the Latin American Heart Rhythm Society .

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

Introduction

A new technology capable of monitoring local impedance (LI) and contact force (CF) has recently been developed. At the same time, there is growing concern regarding catheter ablation performed under fluoroscopy guidance, due to its harmful effects for both patients and practitioners. The aim of this study was to assess the safety and effectiveness of zero-fluoroscopy cavotricuspid isthmus (CTI) ablation monitoring LI drop and CF as well as to elucidate if these parameters can predict successful radiofrequency (RF) applications in CTI ablation.

Methods

We conducted a prospective observational study recruiting 50 consecutive patients who underwent CTI ablation. A zero-fluoroscopy approach guided by the combination of LI drop and CF was performed. In each RF application, CF and LI drop were monitored. A 6-month follow-up visit was scheduled to assess recurrences.

Results

A total of 767 first-pass RF applications were evaluated in 50 patients. First-pass effective RF applications were associated with greater LI drops: absolute LI drops (30.05 ± 6.23 Ω vs. 25.01 ± 5.95 Ω), p = 0.004) and relative LI drops (-23.3 ± 4.9% vs. -18.3 ± 5.6%, p = 0.0005). RF applications with a CF between 5 and 15 grams achieved a higher LI drop compared to those with a CF below 5 grams (29.4 ± 8.76 Ω vs. 24.8 ± 8.18 Ω, p < 0.0003). However, there were no significant differences in LI drop between RF applications with a CF between 5 and 15 grams and those with a CF beyond 15 grams (29.4 ± 8.76 Ω vs. 31.2 ± 9.81 Ω, p = 0.19). CF by itself, without considering LI drop, did not predict effective RF applications (12.3 ± 7.54 g vs. 11.18 ± 5.18 g, p = 0.545). Successful CTI ablation guided by a zero-fluoroscopy approach was achieved in all patients. Only one patient experienced a recurrence during the 6-month follow-up.

Conclusions

LI drop (absolute and relative values) appears to be a good predictor of successful RF applications to achieve CTI conduction block. The optimal CF to achieve a good LI drop is between 5 and 15 g. A zero-fluoroscopy approach guided by LI and CF was feasible, effective, and safe.

Pulmonary vein isolation by means of a novel cryoballoon technology in paroxysmal atrial fibrillation patients: 1-year outcome from a large Italian multicenter clinical registry

INTRODUCTION

Recently, a new cryoballoon (CB) technology (POLARx; Boston Scientific) has come onto the market. Preliminary data have shown that its acute safety and efficacy are similar to those of the first-generation CB. The aim of this study was to assess the medium-term outcome of pulmonary vein isolation (PVI) with the POLARxTM CB in a large multicenter registry.

METHODS

We prospectively collected data on 125 consecutive patients with paroxysmal atrial fibrillation (AF) who underwent PVI by means of a novel CB system. Two cases of transient phrenic nerve palsy occurred, with full recovery in the 48h post procedure; no major procedure-related adverse events were reported. During the 90-day blanking period, 4 (3.2%) patients experienced an early recurrence. After the blanking period, over a mean follow-up of 411 ± 62 days, 19 patients (15.2%) suffered an AF/atrial tachycardia (AT) recurrence. The 1-year freedom from AF/AT recurrence was 86.4% (n = 17): 10 (8%) patients had an AF recurrence, 6 (4.8%) had an AT occurrence and 1 (0.8%) suffered both events. Patients with AF/AT recurrences had both a shorter deflation time and total deflation time. Moreover, CB ablations with measured TTI < 90 s and TTI < 60 s were more frequent in patients without AF/AT recurrence (88.5% and 77.4%, respectively) than in those who experienced at least one AF/AT recurrence (67.5% and 55.0%, p = .001 and p = .005, respectively).

CONCLUSION

The novel POLARx cryo-balloon system is safe and effective for PV isolation, displaying a 1-year freedom from atrial arrhythmia recurrence of 86.4%, which is in line to that reported with AFA-Pro CB or RF ablation.

CLINICAL TRIAL REGISTRATION

Catheter Ablation of Arrhythmias with a High-Density Mapping System in Real-World Practice (CHARISMA). URL: http://clinicaltrials.gov/ Identifier: NCT03793998. Registration date: January 4, 2019.

Insight into contact force local impedance technology for predicting effective pulmonary vein isolation

Background

Highly localized impedance (LI) measurements during atrial fibrillation (AF) ablation have the potential to act as a reliable predictor of the durability of the lesions created.

Objective

We aimed to collect data on the procedural parameters affecting LI-guided ablation in a large multicenter registry.

Methods

A total of 212 consecutive patients enrolled in the CHARISMA registry and undergoing their first pulmonary vein (PV) isolation for paroxysmal and persistent AF were included.

Results

In all, 13,891 radiofrequency (RF) applications of ≥3 s duration were assessed. The first-pass PV isolation rate was 93.3%. A total of 80 PV gaps were detected. At successful ablation spots, baseline LI and absolute LI drop were larger than at PV gap spots (161.4 ± 19 Ω vs. 153.0 ± 13 Ω, p < 0.0001 for baseline LI; 22.1 ± 9 Ω vs. 14.4 ± 5 Ω, p < 0.0001 for LI drop). On the basis of Receiver operating characteristic curve analysis, the ideal LI drop, which predicted successful ablation, was >21 Ω at anterior sites and >18 Ω at posterior sites. There was a non-linear association between the magnitude of LI drop and contact-force (CF) (r = 0.14, 95% CI: 0.13-0.16, p < 0.0001) whereas both CF and LI drop were inversely related with delivery time (DT) (-0.22, -0.23 to -0.20, p < 0.0001 for CF; -0.27, -0.29 to -0.26, p < 0.0001 for LI drop).

Conclusion

An LI drop >21 Ω at anterior sites and >18 Ω at posterior sites predicts successful ablation. A higher CF was associated with an increased likelihood of ideal LI drop. The combination of good CF and adequate LI drop allows a significant reduction in RF DT.

Clinical trial registration

http://clinicaltrials.gov/, identifier: NCT03793998.

Lesion effects in terms of local impedance variations after pulsed-field ablation during pulmonary vein isolation: a case report

Background

To date, no information is available on highly localized impedance (LI) measurements during the ablation of pulmonary veins (PVs) via a new form of energy such as electroporation by means of pulsed-field ablation (PFA).

Case summary

A 55-year-old man with a history of paroxysmal atrial fibrillation was admitted to our hospital for PV isolation (PVI). The procedure was performed with the new multi-electrode PFA catheter (FARAWAVE™). Before energy delivery, a high-density map of the left atrium was constructed with the Rhythmia™ system, while the IntellaNAV Mifi™ OI catheter was used to assess the baseline LI values of the four PVs. A manual tag was used to record the exact position where the IntellaNAV™ catheter measured the LI values for each segment of the vein before and after PVI. The LI values displayed a significant variation after PFA delivery (124.3 ± 5 Ω for baseline LI vs. 96.8 ± 6 Ω after PFA, P < 0.0001) with a mean absolute LI variation of 27.5 ± 7Ω and a mean percentage LI variation of 25.8 ± 8%. The differences between the average LI values pre- and post-PFA were 28.0 ± 5, 26.5 ± 9, 26.8 ± 3, and 28.8 ± 10 Ω for the superior, anterior, posterior, and inferior portions of the PV.

Discussion

This is the first instance of the acute characterization, in terms of LI drop, of antral lesions created by a new PFA system. Local impedance variations at ablation sites seem to be larger than those recorded at successful ablation spots obtained by means of thermal energy sources.

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

Background: Optimal lesion formation during catheter-based radiofrequency current (RFC) ablation depends on electro-mechanical tip-tissue coupling measurable via contact force (CF) and local impedance (LI) monitoring. We aimed to investigate CF and LI dynamics in patients with previous atrial fibrillation (AF) ablation who frequently present with heterogenous arrhythmia substrate.

Methods: Data from consecutive patients presenting for repeat AF or atrial tachycardia ablation using a novel open-irrigated single-tip ablation catheter were studied. RFC applications were investigated regarding CF, LI and the maximum LI drop (∆LI) for evaluation of ablation efficacy. ∆LI > 20 Ω was defined as a successful RFC application.

Results: A total of 730 RFC applications in 20 patients were analyzed. Baseline CF was not associated with baseline LI (R = 0.06, p = 0.17). A mean CF < 8 g during ablation resulted in lower ∆LI (<8 g: 13 Ω vs. ≥ 8 g: 16 Ω, p < 0.001). Baseline LI showed a better correlation with ∆LI (R = 0.35, p < 0.001) compared to mean CF (R = 0.17, p < 0.001). Mean CF correlated better with ∆LI in regions of low (R = 0.31, p < 0.001) compared to high (R = 0.21, p = 0.02) and intermediate voltage (R = 0.17, p = 0.004). Combined CF and baseline LI predicted ∆LI > 20 Ω (area under the receiver operating characteristic curve (AUC) 0.75) better compared to baseline LI (AUC 0.72), mean CF (AUC 0.60), force-time integral (AUC 0.59) and local bipolar voltage (0.55).

Conclusion: Combination of CF and LI may aid monitoring real-time catheter-tissue electro-mechanical coupling and lesion formation within heterogenous atrial arrhythmia substrate in patients with repeat AF or atrial tachycardia ablation.

Assessment of the Need of a Waiting Period after Pulmonary Vein Isolation with the Ablation Index Software

PURPOSE

Since the widespread availability of contact-force sensing catheters, the need of a waiting period after pulmonary vein isolation (PVI) has not been reassessed. We aim to evaluate whether a waiting period is still necessary after PVI guided by the Ablation Index (AI).

METHODS

Prospective, multicenter, randomized study of consecutive patients referred for paroxysmal atrial fibrillation (AF) ablation from May 2019 to February 2020. Patients were randomized in a 1:1 ratio to PVI with versus without a waiting period of 20 minutes. Acute pulmonary vein (PV) reconnection after adenosine challenge was the primary endpoint. A per-protocol analysis was designed to determine whether a strategy of dismissing the waiting period after PVI was noninferior to waiting 20minutes for identifying acute PV reconnection. PVI was guided by tailored AI values and an inter-lesion distance ≤6mm.

RESULTS

During the enrollment period, 167 patients (56% males, mean age of 57±14 years) fulfilled the study inclusion criteria - 84 patients (308 PV) in the waiting period group (group A) and 83 patients (314 PV) in the group without a waiting period (group B). Acute PV reconnection was identified in 3.8% (95% CI, 1.7% to 5.9%) of PVs in the study group B compared to 2.9% (95% CI, 1.0% to 4.8%) of PVs in the group A (p=0.002 for non-inferiority). At 1-year follow-up there was no significant difference in arrhythmia recurrence between groups (9.5% in group A vs. 9.6% in group B, HR 1.03 [95% CI, 0.39-2.73], p=0.98).

CONCLUSIONS

In paroxysmal AF patients submitted to ablation, a tailored PVI guided by the Ablation Index rendered a 20-minute waiting period unnecessary. This article is protected by copyright. All rights reserved.

Targeted ablation of residual pulmonary vein potentials in atrial fibrillation ablation through ultra-high-density mapping: insights from the CHARISMA registry

INTRODUCTION

Low-voltage activity beyond pulmonary veins (PVs) may contribute to the failure of ablation of atrial fibrillation (AF) in the long term. We aimed to assess the presence of gaps (PVG) and residual potential (RAP) within the antral scar by means of an ultra-high density mapping (UHDM) system.

METHODS

We studied consecutive patients from the CHARISMA registry who were undergoing AF ablation and had complete characterization of residual PV antral activity. The Lumipoint^TM (Boston Scientific) map-analysis tool was used sequentially on each PV component. The ablation endpoint was PV isolation (PVI) and electrical quiescence in the antral region.

RESULTS

Fifty-eight cases of AF ablation were analyzed. A total of 86 PVGs in 34 (58.6%) patients and 44 RAPs in 34 patients (58.6%) were found. In 16 (27.6%) cases, we found at least one RAP in patients with complete absence of PV conduction. RAPs showed a lower mean voltage than PVG (0.3±0.2mV vs 0.7±0.5mV, p<0.0001), whereas the mean number of EGM peaks was higher (8.4±1.4 vs 3.2±1.5, p<0.0001). The percentage of patients in whom RAPs were detected through Lumipoint^TM was higher than through propagation map analysis (58.6% vs 36.2%, p=0.025). Acute procedural success was 100%, with all PVs successfully isolated and RAPs completely abolished in all study patients. During a mean follow-up of 453±133 days, 6 patients (10.3%) suffered an AF/AT recurrence.

CONCLUSION

Local vulnerabilities in antral lesion sets were easily discernible by means of the UHDM system in both de novo and redo patients when no PV conduction was present.

CLINICAL TRIAL REGISTRATION

Catheter Ablation of Arrhythmias with a High-Density Mapping System in Real-World Practice (CHARISMA). URL: http://clinicaltrials.gov/Identifier: NCT03793998 This article is protected by copyright. All rights reserved.

Local Impedance Drop Predicts Durable Conduction Block in Patients With Paroxysmal Atrial Fibrillation

OBJECTIVES

This analysis was performed to evaluate the transition of local impedance (LI) drop during pulmonary vein isolation (PVI) to durable block and mature lesion formation based on 3-month mapping procedures.

BACKGROUND

A radiofrequency catheter measuring LI has been shown to be effective for performing PVI in patients with paroxysmal atrial fibrillation. Previous analysis has demonstrated LI drop to be predictive of pulmonary vein segment conduction block during an atrial fibrillation ablation procedure.

METHODS

Fifty-eight patients who had undergone LI-blinded de novo PVI returned for a 3-month mapping procedure. PVI ablation circles were divided into 16 anatomic segments for classification (durable block or gap), and the median LI drop within segments with an interlesion distance of ≤6 mm was compared. A total of 51 data sets met the criteria for segmental analysis of LI performance.

RESULTS

At the 3-month procedure, PV connection was confirmed in at least 1 PV segment in 35 of the included patients. LI drop outperformed generator impedance drop as a predictor of durable conduction block (area under the receiver-operating characteristic curve: 0.79 vs 0.68; P = 0.003). Optimal LI drops were identified by left atrial region (anterior/superior: 16.9 Ω [sensitivity: 69.1%; specificity: 85.0%; positive predictive value for durable conduction block: 97.7%]; posterior/inferior:14.2 Ω [sensitivity: 73.8%; specificity: 78.3%; positive predictive value: 96.9%]). Starting LI before radiofrequency (RF) application was significantly different among healthy, gap, and mature scar tissue and was also a contributing factor to achieving an optimal LI drop (85.2% of RF applications with a starting LI of ≥110 Ω achieved the optimal regional drop or greater).

CONCLUSIONS

LI drop is predictive of durable PV segment isolation. Preablation starting LI is associated with the magnitude of LI drop. These findings suggest that a regional approach to RF ablation guided by LI combined with careful interlesion distance control may be beneficial in patients with paroxysmal atrial fibrillation (Electrical Coupling Information From the Rhythmia HDx System and DirectSense Technology in Subjects With Paroxysmal Atrial Fibrillation [LOCALIZE]; NCT03232645).

Improved procedural workflow for catheter ablation of paroxysmal AF with high-density mapping system and advanced technology: Rationale and study design of a multicenter international study

BACKGROUND

The antral region of pulmonary veins (PV)s seems to play a key role in a strategy aimed at preventing atrial fibrillation (AF) recurrence. Particularly, low-voltage activity in tissue such as the PV antra and residual potential within the antral scar likely represent vulnerabilities in antral lesion sets, and ablation of these targets seems to improve freedom from AF. The aim of this study is to validate a structured application of an approach that includes the complete abolition of any antral potential achieving electrical quiescence in antral regions.

METHODS

The improveD procEdural workfLow for cathETEr ablation of paroxysmal AF with high density mapping system and advanced technology (DELETE AF) study is a prospective, single-arm, international post-market cohort study designed to demonstrate a low rate of clinical atrial arrhythmias recurrence with an improved procedural workflow for catheter ablation of paroxysmal AF, using the most advanced point-by-point RF ablation technology in a multicenter setting. About 300 consecutive patients with standard indications for AF ablation will be enrolled in this study. Post-ablation, all patients will be monitored with ambulatory event monitoring, starting within 30 days post-ablation to proactively detect and manage any recurrences within the 90-day blanking period, as well as Holter monitoring at 3, 6, 9, and 12 months post-ablation. Healthcare resource utilization, clinical data, complications, patients' medical complaints related to the ablation procedure and patient's reported outcome measures will be prospectively traced and evaluated.

DISCUSSION

The DELETE AF trial will provide additional knowledge on long-term outcome following a structured ablation workflow, with high density mapping, advanced algorithms and local impedance technology, in an international multicentric fashion. DELETE AF is registered at ClinicalTrials.gov (NCT05005143).

Comparison of two catheters measuring local impedance: local impedance variation vs lesion characteristics and steam pops

PURPOSE

The size of the distal electrode and the method of measuring local impedance (LI) are different between the IntellaNav MiFi-OI™ (MiFi-OI) and IntellaNav STABLE POINT™ (SP) catheters. We investigated the impact of these differences on LI, efficacy, and safety of radiofrequency (RF) applications.

METHODS

RF applications at a range of powers (30 W, 40 W, and 50 W), contact forces (10 g and 20 g), and durations (10-120 s) were performed in excised porcine hearts (N = 48). LI variation was defined by δLI-drop (= initial LI - post-RF LI) and %LI-drop (= δLI-drop/initial LI) × 100, and the relationship between lesion characteristics and LI variation was compared.

RESULTS

A total of 576 lesions were examined. Although absolute δLI-drop during RF applications was significantly larger for the SP than MiFi-OI catheter (47[31-65]ohm for SP vs 37[24-51]ohm for MiFi-OI, p < 0.0001), %LI-drop was similar (23.3 [15.5-30.6]% in SP vs 24.9[17.3-32.5]% in MiFi-OI, p = 0.10). Although lesions produced by both catheters were similarly correlated with LI variation, the SP catheter produced generally larger lesions (depth; 5.0 [3.7-6.1]mm vs 4.7 [3.3-6.0]mm, p = 0.06; surface areas, 46.9 [36.8-58.8]mm² vs 44.7 [34.3-55.5]mm², p = 0.02; volume, 321 [165-533]mm³ vs 265[141-471]mm³, p = 0.02). Steam pops were similarly observed with both catheters. In both catheters, %LI-drop was superior to δLI-drop in correlation to lesion size (p < 0.0001) and in predicting steam pops (p < 0.01).

CONCLUSIONS

Although no difference in safety profile is observed between MiFi-OI and SP catheters, the SP catheter produces larger lesions. %LI-drop is superior to δLI-drop in correlation to lesion size and in predicting steam pops as well as in normalizing the difference between catheters.

Optimized radiofrequency lesions through local impedance guidance for effective CTI ablation in right atrial flutter

BACKGROUND

Although radiofrequency (RF) catheter ablation of cavo-tricuspid isthmus (CTI) is an established treatment for typical right atrial flutter (RAFL), it remains to be established whether local tissue impedance (LI) is able to predict effective CTI ablation and what LI drop values during ablation should be used to judge a lesion as effective. We aimed to investigate the ability of LI to predict ablation efficacy in patients with RAFL.

METHODS

RF delivery was guided by the DirectSense™ algorithm. Successful single RF application was defined according to a defragmentation of atrial potentials (DAP), reduction of voltage (RedV) by at least 80% or changes on unipolar electrogram (UPC). The ablation endpoint was the creation of bidirectional conduction block (BDB) across the isthmus.

RESULTS

392 point-by-point RF applications were analyzed in 48 consecutive RAFL patients. The mean baseline LI was 105.4±12Ω prior to ablation and 92.0±11Ω after ablation (p<0.0001). According to validation criteria, absolute drops in impedance were larger at successful ablation sites than at ineffective ablation sites (DAP: 17.8±6Ω vs 8.7±4Ω; RedV: 17.2±6Ω vs 7.8±5Ω; UPC: 19.6±6Ω vs 10.1±5Ω, all p<0.0001). LI drop values significantly increased according to the number of criteria satisfied (ranging from 7.5Ω to 19.9). BDB was obtained in all cases. No procedure-related adverse events were reported.

CONCLUSIONS

A LI-guided approach to CTI ablation was safe and effective in treating RAFL. The magnitude of LI drop was associated with effective lesion formation and BDB and could be used as a marker of ablation efficacy.

CLINICAL TRIAL REGISTRATION

Catheter Ablation of Arrhythmias with a High-Density Mapping System in Real-World Practice (CHARISMA). URL: http://clinicaltrials.gov/ Identifier: NCT03793998. This article is protected by copyright. All rights reserved.

[Catheter ablation : Developments and technique selection]

Atrial fibrillation (AF) is the most common arrhythmia and an important risk factor for the occurrence of cardiovascular events. According to current guidelines, rhythm-controlling therapy is recommended only for symptomatic AF. Even in symptomatic AF there is still only a class IIa-recommendation for catheter ablation as initial therapy in paroxysmal AF. Meanwhile, current studies have shown an advantage of the early rhythm control compared to a rate control, as well as a benefit of catheter ablation compared to antiarrhythmic drug (AAD) treatment. The gold standard of catheter ablation for AF therapy is pulmonary vein isolation, which has been mainly radiofrequency-based in the past. However, cryoablation as a first-line therapy of paroxysmal AF is increasingly gaining importance, as the latest studies showed shorter procedure times, lower reintervention rates and improved life quality after cryoablation. Nevertheless, using these standard techniques, the risk of adverse events is still given through collateral damage. The field high-power short duration ablation is currently topic of ongoing AF research, which describes a radiofrequency ablation with higher energy levels, given over shorter duration, with a consecutive lower recurrence rate as well as procedure time. The new ablation techniques also include the pulsed field ablation, which allows ablation through very fast delivery of electrical pulses and causes isolated damage to myocardial cells without collateral damage. This promising technique passed the efficiency and safety testing in preclinical studies. To validate this technique further randomized trials are needed.

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

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.

When local impedance meets contact force: preliminary experience from the CHARISMA registry

PURPOSE

Highly localized impedance (LI) measurements during atrial fibrillation (AF) ablation have emerged as a viable real-time indicator of tissue characteristics and the consequent durability of the lesions created. We investigated the impact of catheter-tissue contact force (CF) on LI behavior during pulmonary vein isolation (PVI).

METHODS

Forty-five consecutive patients of the CHARISMA registry undergoing de novo AF radiofrequency (RF) catheter ablation with a novel open-irrigated-tip catheter endowed with CF and LI measurement capabilities (Stablepoint™ catheter, Boston Scientific) were included.

RESULTS

A total of 2895 point-by-point RF applications were analyzed (RF delivery time (DT) = 8.7±4s, CF = 13 ±±8 g, LI drop = 23 ±±7 Ω). All PVs were successfully isolated in an overall procedure time of 118 ±±34 min (fluoroscopy time = 13 ±±8 min). The magnitude of LI drop weakly correlated with CF (r = 0.13, 95% confidence interval (CI): 0.09 to 0.16, p < 0.0001), whereas both CF and LI drop inversely correlated with DT (r = -0.26, 95%CI: -0.29 to -0.22, p < 0.0001 for CF; r = -0.36, 95%CI: -0.39 to -0.33, p < 0.0001 for LI). For each 10 g of CF, LI drop markedly increased from 22.4 ± 7 Ω to 24.0 ± 8 Ω at 5 to 25 g CF intervals (5-14 g of CF vs 15-24 g of CF, p < 0.0001), whereas it showed smooth transition over 25 g (24.8 ± 7Ω at ≥ 25 g CF intervals, p = 0.0606 vs 15-24 g of CF). No major complications occurred during the procedures or within 30 days.

CONCLUSIONS

CF significantly affects LI drop and probable consequent lesion formation during RF PVI. The benefit of higher contact (> 25 g) between the catheter and the tissue appears to have less impact on LI drop.

TRIAL REGISTRATION

Catheter Ablation of Arrhythmias With High Density Mapping System in the Real World Practice (CHARISMA). URL: http://clinicaltrials.gov/ Identifier: NCT03793998.

Radiofrequency ablation to achieve durable pulmonary vein isolation

Pulmonary vein isolation (PVI) by radiofrequency (RF) ablation is an important alternative to antiarrhythmic drugs in the treatment of symptomatic atrial fibrillation. However, the inability to consistently achieve durable isolation of the pulmonary veins hampers the long-term efficacy of PVI procedures. The large number of factors involved in RF lesion formation and the complex interplay of these factors complicate reliable creation of durable and transmural ablation lesions. Various surrogate markers of ablation lesion formation have been proposed that may provide information on RF lesion completeness. Real-time assessment of these surrogates may aid in the creation of transmural ablation lesions, and therefore, holds potential to decrease the risk of PV reconnection and consequent post-PVI arrhythmia recurrence. Moreover, titration of energy delivery until lesions is transmural may prevent unnecessary ablation and subsequent adverse events. Whereas several surrogate markers of ablation lesion formation have been described over the past decades, a 'gold standard' is currently lacking. This review provides a state-of-the-art overview of ablation strategies that aim to enhance durability of RF-PVI, with special focus on real-time available surrogates of RF lesion formation in light of the biophysical basis of RF ablation.

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

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.