The feasibility and effectiveness of a streamlined single‐catheter approach for radiofrequency atrial fibrillation ablation

Abstract Background Catheter ablation for atrial fibrillation (AF) traditionally requires the use of circular mapping catheter (CMC) for pulmonary vein isolation (PVI). This study aimed to assess the feasibility and effectiveness of a CMC‐free approach for AF ablation performed by a contiguous optimized (CLOSE) ablation protocol. Methods A CLOSE‐guided and CMC‐free PVI protocol with a single transseptal puncture was attempted in 67 patients with AF. Left atrial (LA) CARTO voltage mapping was performed with the ablation catheter pre‐ and postablation to demonstrate entry block into the pulmonary veins, and pacing maneuvers were used to confirm exit block. Results The CMC‐free approach was successful in achieving PVI in 66 (98.5%) cases, with procedure time of 148 ± 32 minutes, ablation time of 27.5 ± 5.7 minutes, and fluoroscopy time of 7.8 ± 1.0 minutes. First‐pass PVI was seen in 58(86.5%) patients, and pacing maneuvers successfully identified the residual gap in eight of the other nine cases. No complication was observed. At 12 months follow‐up, 60 (89.6%) patients remained free from AF. The CMC‐free approach resulted in a cost saving of £47,190. Conclusion A CMC‐free CLOSE‐guided PVI approach is feasible, safe, and cost‐saving, and is associated with excellent clinical outcomes at 1 year.

residing in the LA is therefore potentially complex, skill-dependent, time-consuming and has required double transseptal punctures or single-puncture double-wiring transseptal catheterization techniques.
Recently, the use of a weighted formula (Ablation Index, AI), that incorporates power, contact force (CF), and time, has yielded superior rates of durable pulmonary vein isolation (PVI) and freedom from arrhythmia. 4,5 In addition, use of automated lesion tagging, and adherence to stringent intertag distance (ITD) targets as part of the contiguous lesion optimized (CLOSE) protocol has played an integral role in minimizing gaps along ablation lines. [6][7][8] With the very high first-pass PVI rates observed with CLOSE ablation (as high as 97% in our experience 5 ), it is debatable whether a circular mapping catheter (CMC) is still needed, but the feasibility of a CMC-free CLOSE ablation approach has not been studied. In this prospective study, we evaluated the feasibility of a single transseptal CMC-free approach with contiguous AI-guided PVI, and assessed the clinical efficacy of this technique over a 12-month follow-up period.

| Patient population
The study population comprised consecutive patients who underwent first-time RF PVI for symptomatic drug-refractory AF at our institution between April 2017 and June 2018. All cases were done by operators who have been using AI guidance for AF ablations since November 2014, and have each performed over 200 such cases.

| Compliance with ethical standards
Each patient provided written informed consent prior to the procedure. Outcome data were extracted from an institutional review board-approved registry. The study was approved by the institutional ethics committee and performed in accordance with the ethical standards as laid down in the 1964 Declaration of Helsinki and its later amendments or comparable ethical standards. All patients had PVI-only in this study unless they had documented cavo-tricuspid-isthmus (CTI)-dependent atrial flutter, in which case they also received CTI ablation. No additional ablation was performed in any patient.

| AF ablation procedure
Following WACA, LA electroanatomical mapping was performed with the ablation catheter placed just inside the WACA to validate entry block and to assess for sites of reconnection ( Figure 1A,B). were identified by measuring conduction times along the WACA and at the carina during CS pacing ( Figure 3). If PVI was not achieved with ablation of 2 or more distinct sites along the WACA, a CMC was taken to localize the breakthrough site(s).

| Patient follow-up and clinical outcomes
Patient follow-up was conducted as per local standard practice with clinical reviews at 3, 6, and 12 months with mandatory 12-lead electrocardiograph (ECG) at each follow-up visit, and supplementary symptomdriven ambulatory monitoring if required. All patients discontinued their antiarrhythmic medications (Class I and III) following the initial blanking period of 3 months. The rates of recurrence of atrial arrhythmia, defined as >30 seconds of any atrial arrhythmias (AF, flutter, or atrial tachycardia) with ECG documentation after the initial 3-month blanking period, were captured over the 1-year follow-up period. For survival analysis (survival free from atrial arrhythmia), patients were censored at 1 year if no atrial arrhythmia had occurred or at the date of last follow-up.

| Statistical analysis
Continuous variables were expressed as mean ± SD for normally dis-

| RE SULTS
A total of 67 consecutive patients underwent RF PVI procedures for paroxysmal and persistent AF during the study period using singlecatheter approach.   The RF ablation time was 27.5 ± 5.7 minutes. The mean procedure duration was 147.9 ± 32.4 minutes, mean fluoroscopy time was 7.8 ± 5.4 minutes, and mean radiation exposure was 806.1 ± 539.5 mGy cm 2 . These were significantly shorter than the mean procedure time, fluoroscopy time, and radiation exposure seen with our AI guided AF ablation procedures using a CMC catheter 5 : 175 ± 31, 11.9 ± 7.7 minutes, and 1,656 ± 1,425 mGy cm 2 , respectively, P < .001 for all.

| Procedural details
There were no major procedural complications seen.

| Follow-up and clinical outcomes
The mean follow-up of the study was 390 [IQR 138] days.
Arrhythmia recurrence, defined as the absence of AF/atrial flutter/atrial tachycardia following a 3-month blanking period after a single procedure off antiarrhythmic medications, was seen in seven

| Cost implications of the singlecatheter approach
The cost of a CMC catheter, and a transseptal sheath at our institution are £625 and £90, respectively. These costs were saved in 66 of the 67 cases to give a total cost saving of £47, 190 compared to our traditional PVI approach that utilizes two transseptal sheaths and a CMC.

| The reliability of assessment of conduction block with a single-catheter approach
Since the discovery of PV triggers, successful electrical isolation of the PVs has been regarded as the cornerstone of all AF ablations. 1 The use of CMC has since been the widely accepted means for assessment of conduction breakthrough from the PVs. As the PVI procedure evolved over the years, the ablation level shifted from the PV ostia to the LA antra to increase the efficiency of PVI and to reduce the risk of PV stenosis. The conventional CMC placement at the PV ostia has made the earliest potentials recorded by the CMC less relevant and reliable because of the variable anatomy of the veno-atrial junction contributing to both anatomical and functional conduction blocks. 9 It is therefore arguable that for first-time PVI procedures, the ablation catheter may provide greater flexibility and precision in maneuvering around the antral region for assessment of conduction block. Previous studies have demonstrated that singletip catheter was capable of assessing PVI based on the loss of pace capture along the lesion sets. [10][11][12] Although this method is highly predictive of PVI, this method could be confounded by several issues. First, poor catheter-tissue contact may masquerade as loss of pace capture although this could be circumvented by ensuring CF to be at least 10 g. 12 Even with adequate CF, this however failed to address the challenging issue of obtaining convincing near-field capture because of the oversaturation of pacing artifact obliterating the antral potentials. Second, infrequently epicardial fibers may exist to provide "concealed" conduction breakthroughs within the antrum typically at the carina level, thereby bypassing the endocardial ablation line to provide a false negative phenomenon. However, the use of CMC in conventional workflow is not infallible to these "concealed" antral PV conduction, often necessitating high-density mapping to resolve this issue. 13 In this study, we elected to validate PVI not only by collecting antral voltage maps pre-and postablation but also by demonstrating exit block of PV ectopy thereby obviating the need for pacing adjacent to the PV sleeve unless we failed to elicit PV ectopy during the manipulation of the ablation catheter within the PV ostium. Using this method, we managed to avoid the aforementioned pitfalls.
The two-catheter setup, however, does allow for differentiation of the far-field LA appendage potentials without resorting to limiting the pacing output. 14 Although far-field potentials from LA appendage and superior vena cava could potentially pose diagnostic challenges in validating PVI especially at the anterior aspects of the left and right superior PV, we find that the comparison of timing measurements during CS pacing from pacing spike to either the signals of ablation catheter in LA appendage or with the surface P-wave would aid in addressing the issue without resorting to complex pacing maneuvers ( Figure 2). Importantly, if residual PV gaps were present following initial delivery of PV encirclement lesion sets, judicious timing measurements between pacing spikes during CS pacing and the PV signals at the roving ablation catheter with the aid of CARTO-VisiTag TM and ITD ( Figure 3A) allows precise localization of the earliest entrance conduction ( Figure 3B) with successful PVI ( Figure 3C).
It is important to note that the majority of residual conduction after a CLOSE-guided PVI occurs along the unablated intervenous carinal tissue. This knowledge helps to quickly home in on the likely sites of residual conduction in cases where first-pass isolation has not been achieved.

| Safety and cost-effectiveness of a minimalistic approach
The inherent risk of several complications of AF ablation can potentially be reduced with a single-catheter approach. The avoidance of second sheath/catheter manipulation and limiting the number of transseptal punctures may reduce the risk of tamponade. The potential of cerebral embolism when exchanging CMC with ablation catheter through a single transseptal sheath strengthens the case for a single-catheter, single sheath approach. 23 Although a rare complication, the risk of CMC entrapment in the mitral valve apparatus remain another concern, adding further to the safety profile of the single-catheter approach. 24 Healthcare economic principles dictate conscientious use of consumables and an efficient AF ablation workflow. This study demonstrated the cost saving implication of the single-catheter approach in terms of lower costs of consumables.

| Limitations
Several limitations need to be acknowledged in this study. First, patient recruitment into this study is nonrandomized, although consecutive in nature. Second, the differentiation of PV potentials from far-field potentials, as well as localization of residual gap(s) after firstpass isolation require patients to be in sinus rhythm. Therefore, for accurate PVI validation using the single-catheter approach, patients in AF need to be electrically cardioverted. Finally, it is improbable to ascribe our excellent ablation outcome at 12 months to the singlecatheter setup per se. More likely than not, it is strict adherence to the CLOSE protocol that permits this streamlined single-catheter approach, thereby obviating the need of a CMC to achieve similar, if not better outcomes. This may not be replicable by relatively inexperienced operators.

| CON CLUS ION
A streamlined single-catheter workflow for contiguous AI-guided AF ablation for PVI is safe and efficient, while delivering cost savings when compared to the conventional two-catheter ablation setup.
This approach is also associated with excellent ablation outcome at 12 months.

CO N FLI C T O F I NTE R E S T
DG received research funding from Biosense Webster and participated on research grants supported by Johnson and Johnson.

E TH I C A L A PPROVA L
All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional research board (IRB number: LHCH-R&D 1117, approved on 18th March 2017) and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards.