Zero‐fluoroscopy transseptal puncture guided by right atrial electroanatomical mapping combined with intracardiac echocardiography: A single‐center experience

Abstract Background Right atrial electroanatomical mapping may be combined with SoundStar 3D diagnostic ultrasound catheter (EAM‐ICE) as a zero‐fluoroscopy procedure for radiofrequency catheter ablation (RFCA). We aimed to evaluate the efficiency and safety of zero‐fluoroscopy transseptal puncture guided by EAM‐ICE and fluoroscopy combined with intracardiac echocardiography (F‐ICE) in patients with paroxysmal atrial fibrillation (PAF). Hypothesis Zero‐fluoroscopy transseptal puncture is an effective and safe procedure. Methods This study had a prospective design. A total of 57 patients with PAF were enrolled and assigned to two groups. Twenty‐seven patients were enrolled in the EAM‐ICE group, and 30 patients were enrolled in the F‐ICE group. Results There were no statistically significant differences in baseline patient characteristics between groups. Transseptal puncture was successful in all patients (57/57, 100%). Total procedure time and duration of transseptal puncture were lower in the F‐ICE group (199.4 ± 26.0 minutes vs 150.7 ± 22.1 minutes, P = 0.000; 118.4 ± 19.7 vs 70.5 ± 13.5 minutes, P = 0.000). There was no use of fluoroscopy in the EAM‐ICE group (0 mGy vs 70.5 ± 13.5 mGy); the duration of fluoroscopy in the EAM‐ICE group was negligible (0 minutes vs 5.4 ± 1.9 minutes). No procedural complication occurred in either group. Conclusions EAM‐ICE guided zero‐fluoroscopy transseptal puncture is an effective and safe procedure.


| INTRODUCTION
Fluoroscopy is used to perform electrophysiological studies and catheter ablations. However, radiation exposure can threaten the health of both doctors and patients. 1,2 Furthermore, radiation protection suits are heavy and may cause doctors musculoskeletal injury. The "as low as reasonably achievable" principle advocates limited radiation usage and proposes several methods to reduce radiation exposure, 3 such as zero-fluoroscopy procedures. Zero-fluoroscopy procedures have recently become feasible because of the development of contact force-sensing catheters, electroanatomical mapping systems (EAMs), and intracardiac echocardiography (ICE) probes. 4 ICE-guided radiofrequency catheter ablation (RFCA) has been studied in this context. [5][6][7] However, few studies have investigated the application of ICE to procedures involving the atrial septum.
The foramen ovale is a unique anatomical structure located in thick muscle. During EAM, electrography yields low-voltage readings for the foramen ovale. Whether this information can increase the success of transseptal puncture remains to be determined. No relevant studies have been conducted in Chinese populations. In this study, we developed a method for the combination of EAM with SoundStar 3D diagnostic ultrasound catheter (EAM-ICE) to perform circumferential pulmonary vein isolation (CPVI). The efficacy and safety of EAM-ICEguided transseptal puncture and catheter ablation are discussed below.

| Study design and population
A prospective, controlled trial was conducted at Beijing Anzhen Hospital. During the period from June 2019 to October 2019, 57 consecutive patients with paroxysmal atrial fibrillation were enrolled in the study. Patients were divided into two groups.
This study was approved by the Beijing Anzhen Hospital Medical Ethics Committee. All participants evaluated in this trial provided written informed consent.
The inclusion criteria were as follows: (a) adults aged 18 to 80 years; (b) previous diagnosis with paroxysmal atrial fibrillation (PAF), defined as AF terminating spontaneously or AF onset <7 days before RFCA, with verification of AF using 12
Using the map, a 10-polar diagnostic catheter was placed inside the CS. The ICE probe was then placed inside the RA using an 11-F introducer. The position of the atrial septum was confirmed by ICE ( Figure 2).

Left atrial mapping
Under the direction of ICE and EAM, a three-dimensional (3D) left atrium (LA) map was created to visualize the anatomy of the LA and pulmonary veins. Not only the pulmonary veins and their ostia but also the left atrial appendage (LAA) was carefully mapped. We also checked the LAA for thrombosis.

Advancing the transseptal sheath into the SVC
Before inserting the J-type guide-wire into the SVC, we measured the distance from the site of puncture to the junction where the sternum met the second rib. We also marked the same distance on the non-steerable SL1 sheath (Agilis TM, Fast Cath, Abbott, Abbott Park, IL). A clip-pin cable was used to connect the J-type guide-wire to the Carto system for navigation. One side of each connector was clipped onto the guide-wire; the other side was con-  Third, a pressure transducer was used to evaluate puncture success.
After a successful puncture had been confirmed, the sheath-dilator assembly was advanced over the needle. After needle withdrawal, a long wire was inserted across the LA into the left superior pulmonary vein (LSPV). The sheath-dilator was advanced into the LA. The dilator and long wire were withdrawn. Then, a bolus of physiological solution was injected through the sheath. A shadow of the solution bolus visualized on ICE provided confirmation that the LA had been penetrated. The ablation catheter was advanced inside the LA (Figure 3).

| Fluoroscopy-guided transseptal puncture
For patients in the F-ICE group, the procedure was performed under fluoroscopic and ICE guidance.

Preparation
To access the heart, bilateral femoral venous puncture was performed. A guide-wire for the long sheath was inserted into the right femoral vein; a 6-F introducer and an 11-F introducer sheath were inserted into the left femoral vein. ICE was used to visualize the anatomy of the foramen ovale on the side facing the left pulmonary vein.
Then, a 10-polar diagnostic catheter was inserted into the CS under fluoroscopic guidance.

Left atrial mapping
Under the direction of ICE and EAM, a 3D LA map was created to visualize the anatomy of the LA and pulmonary veins.
F I G U R E 3 Transseptal puncture with electroanatomical mapping combined with diagnostic ultrasound catheter (EAM-ICE). A, The long sheath was placed into the SVC through the guide-wire, which was then replaced with the trans-septal needle. The tip of the needle was inserted into the SVC (yellow circle). B and C, After withdrawal of the sheath-dilator-needle assembly, the tip the needle was oriented toward the atrial septum. The needle can be seen facing toward the septum in C. D, Under ICE direction, the trans-septal needle was used to puncture the atrial septum. When the trans-septal needle was pushed toward the atrial septum, a tenting phenomenon could be seen on ICE. E, After a rapid movement of the transseptal needle through the dilator succeeded in puncturing the atrial septum, a small bolus of physiological solution was used to confirm that the needle was inside the left atrium. The shadow created by the bolus can be seen on ICE.

| Catheter ablation
Point-by-point CPVI was performed using irrigated ablation catheters (Thermocool Smarttouch; Biosense Webster) in power control mode at 35 W (irrigation flow 17 mL/min). Radiofrequency applications were performed with Visitag (Carto, Biosense Webster) guidance with catheter stability (2.5 mm for 3 seconds) and contact force (CF; >3 g for 25% of time) settings. The ablation index (AI) targeted at the anterior LA wall was 500, and the AI targeted at the posterior wall was 400. During ablation, an ICE probe was placed in the right ventricle to monitor the pericardium. Heparin was given during the procedure to maintain an activated clotting time between 300 and 350.

| Baseline evaluation
Patients' baseline characteristics (ie, age, sex, body mass index [BMI], and past history) were assessed. Echocardiographic findings (ie, left ventricle ejection fraction, LA anteroposterior diameter) were also recorded.

| Randomization, treatment allocation, and outcomes
Subjects fitting the inclusion and exclusion criteria were assigned to the EAM-ICE or F-ICE group. The primary outcome of this trial was the rate of successful transseptal puncture. The secondary outcomes of this trial were the rates of major complications (ie, cardiac perforation, hydropericardium, malignant arrhythmia, sudden cardiac death, atrial esophageal fistula, and acute myocardial infarction).

| Statistical analysis
Data analysis was performed with SPSS statistical software (IBM, Version 23). Normally distributed continuous variables are expressed as means ± SD; non-uniformly distributed data are expressed as medians (Q1 and Q3). Between-group comparisons of means were analyzed by independent-samples t test for normally distributed data and by Mann-Whitney U test for non-uniformly distributed data. A P-value <0.05 was considered statistically significant.

| Baseline characteristics
This study included 57 patients, 42 (73.7%) of whom were male. A total of 27 (47.4%) patients were enrolled in the EAM-ICE group. Table 1. There were no statistically significant differences in baseline patient characteristics between groups.

| Procedural data
We divided the procedure of transseptal puncture into several steps to evaluate the differences between groups.

| Outcomes
Trans-septal puncture was successful in all cases included in the study (57/57, 100%). We also evaluated total procedure time and transseptal duration in the EAM-ICE and F-ICE groups. Total procedure duration was defined as the duration of the patient's stay in the operating room. In the EAM-ICE group, the duration of trans-septal puncture was considered to be the time required for mapping the RA and   In recent studies, the tenting phenomenon that occurs during ICE was used to direct transseptal puncture. 9,10 Baykaner et al. 11 performed zero-fluoroscopy transseptal puncture under the direction of ICE by placing the ablation catheter onto the atrial septum, which created mild tenting and allowed the position of the sheath to be confirmed. The authors of the study then replaced the ablation catheter Total procedure duration was defined as the duration of the patient's stay in the operating room. b In the EAM-ICE group, trans-septal duration included mapping the right atrium (RA) and foramen ovale with EAM, mapping the left atrium (LA) and foramen ovale with ICE, advancing the long wire and sheath into the SVC, and transseptal puncture. In the F-ICE group, transseptal duration included LA mapping, advancing the long wire and sheath into the SVC, and transseptal puncture. The authors dragged the ablation catheter, which allowed the tip of the catheter to jump to the region of the foramen ovale. 19 However, this manuscript did not provide detailed information.

| EAM vs ICE for mapping the foramen ovale mapping
Base on this anatomical characteristic, we decided to perform zero- we were able to connect the guide-wire and transseptal needle to the Carto system, which allowed us to visualize the tip of this assembly as a bipolar electrode. This procedure, along with the necessary adjustments, required 15 minutes. During the procedure, an ICE probe was used to verify that the technique described was feasible for mapping the anatomy of the foramen ovale, coronary sinus, and LA and to ensure that the procedure was safe. In contrast, in the F-ICE group,

| LIMITATIONS
We only analyzed acute outcomes. AF recurrence and long-term success rates were not analyzed in this trial, which limits the strength of our findings. Patients were not grouped in a random fashion, which limits the strength of the conclusions made from comparisons between EAM-ICE and F-ICE.

| CONCLUSION
It is effective and safe to perform the EAM-ICE procedure. Thus, the use of a zero-fluoroscopy approach for PAF is feasible.