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Zero‐fluoroscopy catheter ablation for atrial fibrillation: a transitional period experience

Abstract Background Radiofrequency catheter ablation for atrial fibrillation (AF) without using fluoroscopy has been getting popular. In this study, we reported the transition period experience of the zero‐fluoroscopy procedure by an experienced operator and shared our zero‐fluoroscopy protocol. Method A total of consecutive 30 AF ablation cases attempted to be treated without fluoroscopy were investigated. Ten serial cases were grouped as fluoroscopy‐guided period, and period 1‐3 in chronological order. All zero‐fluoroscopy attempted cases were assisted with an intracardiac echocardiography device with a three‐dimensional electroanatomical system. Results Complete zero‐fluoroscopy procedure was achieved at the 6th case during the transitional period. During the first period, the total procedure time slightly increased in, but afterward, procedure time was continuously decreased, and it became significantly shorter in the third period than the previous fluoroscopy‐guided period. Any additional use of fluoroscopy during the transitional period was mainly for transseptal puncture and diagnostic catheter placement into the coronary sinus. Pulmonary vein isolation was achieved in all patients, and there was one case of hemodynamically insignificant moderate amount pericardial effusion. Conclusion For an experienced operator, complete zero‐fluoroscopy AF ablation might be achieved safely and feasibly within 5‐10 cases. Fluoroscopy equipment backup might be useful during the learning period for beginners in the zero‐fluoroscopy procedure.

successful attempts to reduce radiation exposure have been achieved. 4,5 Accordingly, the safety and efficacy of a nonfluoroscopy technique for atrial fibrillation (AF) catheter ablation have been recently reported in various studies. [6][7][8] Despite the reported favorable results, there are several concerns about the zero-fluoroscopy procedure. 9 Near-zero or zero-fluoroscopy procedures are becoming increasingly popular because of the development of new technologies. In a randomized trial, ICE and the CARTO® 3 electroanatomical mapping system with contact-force sensors, when used together, enabled the operators to achieve zero-fluoroscopy time during left atrial mapping and ablation without prolongation of the procedure time, with similar efficacy and safety profile as conventional fluoroscopy-guided procedures. 10 Fluoroscopy-guided AF procedures have existed for a long time, and in recent years, complications because of radiation exposure have been largely reduced by the use of pulsed fluoroscopy with low frame rates and maximal collimation. 11,12 On the other hand, the safety of the zero-fluoroscopy procedure has not yet been fully demonstrated. 13 There are difficulties in changing the existing procedural protocol because of the risks that may arise during the transitional period of the new technique, considering its risks and benefits.
In this study, we reported a single-center experience during the transitional period from the conventional fluoroscopy to compete zero-fluoroscopy period with the initial serial 30 cases using CARTO-3 mapping system. Furthermore, we also aimed to describe our procedure protocol how each step was performed without fluoroscopy exposure.

| Patient population
A total of 30 serial cases of AF catheter ablation intended for the zero-fluoroscopy procedure, were analyzed. Patients were divided into three groups according to the order of the procedure. The first 10 patients were grouped as "period 1," the next 10 patients as "period 2," and the last 10 patients as "period 3" in chronologic order. Procedure outcome was compared to the most recent serial AF cases (n = 30) with conventional fluoroscopy technique before the transitional period. To minimize the interoperator bias, only one operator (MJC) with the same first assistant physician participated in the procedure during the study period.
All 30 patients had symptomatic paroxysmal or persistent AF, and documented failure of or intolerance to at least one antiarrhythmic drug. All patients continued their use of oral anticoagulants except on the day of the procedure. All antiarrhythmic drugs were discontinued >1 week before the ablation. This study was based on the experience of a single tertiary center performing around 150 AF ablation procedures annually. Procedure-related data were collected in the same manner according to the form determined by the institution and were reviewed retrospectively for the study.

| Preprocedural preparation
All patients underwent a preprocedural cardiac computed tomography (CT) scan within 12 hours before the procedure for evaluating abnormal intracariac structure, thrombus, or coronary artery stenosis. All patients in our series were planned to undergo an ablation procedure with the fluoroless approach. Nevertheless, a fluoroscopy system was prepared for its immediate use when needed. An electrophysiology laboratory system fully equipped with the CARTO® 3 electroanatomical mapping system (Biosense-Webster, Diamond Bar, CA, USA), with the Confidence® module for CARTOSOUND®, CARTO VISITAG®, and CARTO VISITAG® with Ablation Index, was used.

| Vascular and intracardiac access
Two vascular accesses were obtained only in the right femoral vein using a modified Seldinger technique for sheath placement (one long wire and one short 8-Fr sheath). The ICE catheter (SOUNDSTAR®, Biosense Webster) was carefully introduced into the femoral vein via the short sheath and advanced to the inferior vena cava while observing the vessel lumen. During catheter advancement, the direction could be visualized on CARTO® 3. For long-wire advancement to the superior vena cava, the long wire can be visualized by ICE ( Figure S1).

| ICE-guided transseptal puncture
The ablation catheter was introduced into the left innominate vein guided by contact force, and the catheter direction was visualized in the mapping screen. Then, the SL-1 sheath was advanced until a sheath error sign was detected ( Figure S2). Then, the ablation catheter was pulled out and a transseptal needle (Brockenbrough needle; Medtronic) with a dilator at the 4-5 o'clock position was advanced. The ICE catheter should be fixed to show the fossa ovalis, aortic root, and superior vena cava, in order to visualize the downward movement of the sheath and the dilator ( Figure S3A and Video S1). The operator can see the sheath system approaching the right atrium on the screen of the ICE device, and feel the beating heart through the fingertips of the right hand. When the sheath system is entered into the fossa ovalis, the septum is pushed and tented by the system ( Figure S3B). By rotating the ICE catheter, it is possible to determine whether the puncture site is close to the anterior or posterior rim. Finally, the Brockenbrough needle was advanced to puncture the septum.

| Cardiac structure marking on the 3D image
It is useful to mark the location of the septal puncture site and left atrial wall and the esophageal geometry on the CARTO-SOUND image ( Figure S4). The left atrial volume is most accurate when measured on the ICE image because this image shows the left atrium in real-time without any catheter pushing. If the atrium is markedly dilated, the left atrial ICE view may not be useful in demarcating the important structures. Therefore, it is useful to advance the ICE catheter into the left atrium and map the left atrial wall.

| Coronary sinus catheter placement
Through the sheath used for the ICE catheter, the diagnostic catheter was advanced to the right atrium. We usually use only one duodecapolar catheter (DuoDeca Livewire™; Abbott Laboratories) for the right atrium and the left atrium. The catheter can be visualized on the screen, and the diagnostic catheter can be easily introduced into a desirable location ( Figure S5).

| Pulmonary vein isolation
Ablation was performed using a Navistar Thermocool catheter

| Ripple mapping-guided checking for complete isolation
Sinus rhythm was restored with internal electrical cardioversion when the patient's rhythm was still AF after pulmonary vein iso- The unique visual representation of bipolar voltage assists in the identification of multicomponent signals and associated activation patterns. In the ripple map, the threshold of bipolar voltages for display as a dynamic bar was set at 0.03-0.05 mV, which prevented baseline electrical noise from being displayed on the map.

| Outcome
Any kind of procedure-related complications was counted as safety outcomes, including procedure-related stroke or bleeding, cardiac tamponade, or vascular complications. The feasibility was evaluated according to acute pulmonary vein isolation, residual potential, and early reconnection. A total procedure time, a total ablation time, a fluoroscopy time, and a time for transseptal puncture were recorded.

| Patient characteristics
As described in Table 1

| Procedural safety and feasibility outcome
There was one moderate amount of pericardial effusion event in the 15th patient of zero-fluoroscopy cases. However, there were no procedure-related stroke or bleeding events ( Table 2)

| Transitional curve
The total procedure time, total ablation time, transseptal puncture time, and fluoroscopy exposure time were significantly reduced after successfully changed from conventional fluoroscopy-guided to zero-fluoroscopy procedure (Figure 1).
The completely zero-fluoroscopy procedure was achieved at 6th case in zero-fluoroscopy transitional period 1 (Figure 2). During period 2 and 3, there was no case using fluoroscopy ( Figure 1A).
The total procedure time has gradually decreased from period 1 to 3. It has a large fluctuation during period 2, but significantly decreased during period 3 compared to the fluoroscopy-guided period (113.3 ± 24.8 minutes vs 194.4 ± 43.3 minutes, P < .001, Figure 1B).
Total ablation time was slightly decreased during zero-fluoroscopy transitional period, but there was no statistically significant difference among groups ( Figure 1C). The average time for transseptal puncture was significantly decreased in period 3 compared to fluoroscopy-guided period ( Figure 1D).

| D ISCUSS I ON
In this study, we reported that a transition to completely zero-fluoroscopy approach for AF catheter ablation could be performed by an experienced operator. Pulmonary vein isolation was achieved in all patients. The early transition period was relatively short, and there were only five cases that needed minimal fluoroscopy at the initial stage (period 1). The total procedure time during the study period rapidly decreased thereafter.

TA B L E 2 Procedure outcome
This approach has several advantages. First, the potential radiation hazard for both physicians and patients is completely none.
Second, wearing a heavy lead apron during a procedure with a long duration in multiple cases can cause musculoskeletal disorders in the operators and physicians. 14 Third, real-time visualization of important structures (interatrial septum or coronary sinus) with intracardiac echocardiography seems to be beneficial for patient safety.
The main goal of an AF ablation procedure is pulmonary vein isolation, and it is sometimes necessary to perform adjunctive ablations. 11  Recently, many studies have reported the feasibility and safety of the zero-or near-zero fluoroscopy AF ablation procedure. 6,10,18,19 In a study by Sommer  safety. For the zero-fluoroscopy procedure in this study, the learning period was considered to be relatively short, and completely zero-fluoroscopy was achieved in only four cases after changing the protocol.
Radiation hazard should never be overlooked. With radiation exposure, the risk of cataract or dermatitis is elevated in interventional cardiologists and in patients. 3,22 The average patient dose for AF ablation is known to be 15 mV, and as a general rule of thumb, the absolute lifetime risk of fatal cancer for an adult increases by 0.05% for every 10 mSv of exposure. 1,23 The most active and experienced interventional cardiologists have a personal annual radiation dose exposure of about 5 mSv, which is three times higher than that of radiologists and nuclear physicians. 24 Awareness of the risks associated with radiation exposure to patients and medical staff has significantly increased recently. 1 This study has several limitations. First, this study was based on the experience of a single center that performs around 150 AF ablation procedures annually. Depending on previous experience, the difficulty of zero fluoroscopy may be different. According to our experience, practitioners who are experienced in ICE had little difficulty in transitioning to the zero-fluoroscopy approach. Second, the number of cases is still small to confirm the safety of zero-fluoroscopy procedure. The patient safety is the most important concern; thus, it is essential to prepare fluoroscopy equipment for its imme- another center or another operator should be performed.

| Conclusion
During the transition period, complete zero-fluoroscopy ablation of AF could be achieved safely and feasibly. The zero-fluoroscopy technique decreased total procedure or septal puncture time significantly, saving the patients and physicians from radiation hazard. Fluoroscopy equipment backup and preprocedural imaging might be useful for the initial period of applying the zero-fluoroscopy procedure.

CO N FLI C T O F I NTE R E S T
This study protocol was approved by the institutional review board that also waived the need for informed consent, and was conducted