J A C C : C L I N I C A L E L E C T R O P H Y S I O L O G Y V O L . 5 , N O . 3 , 2 0 1 9

ª 2 0 1 9 B Y T H E A M E R I C A N C O L L E G E O F C A R D I O L O G Y F O U N D A T I O N

P U B L I S H E D B Y E L S E V I E R

Initial Result of Antrum Pulmonary Vein

Isolation Using the Radiofrequency Hot-Balloon Catheter With Single-Shot TechniqueHiro Yamasaki, MD, Kazutaka Aonuma, MD, Yasutoshi Shinoda, MD, Yuki Komatsu, MD, Keita Masuda, MD,Naoaki Hashimoto, MD, Eikou Sai, MD, Fumi Yamagami, MD, Yuta Okabe, MD, Yasuaki Tsumagari, MD,Yuichi Hanaki, MD, Hiroaki Watanabe, MD, Takeshi Machino, MD, Kenji Kuroki, MD, Yukio Sekiguchi, MD,Akihiko Nogami, MD, Masaki Ieda, MD

ABSTRACT

ISS

Fro

rec

de

thi

All

sti

the

Ma

OBJECTIVES This study sought to determine the feasibility of a novel simplified ablation protocol targeting only the

pulmonary vein antrum using the radiofrequency hot-balloon catheter in patients with paroxysmal atrial fibrillation.

BACKGROUND Radiofrequency hot-balloon (RHB) catheter has been recently introduced into clinical practice for

pulmonary vein isolation (PVI). The authors hypothesized that a novel simplified ablation protocol targeting only the PV

antrum with energy application for a longer time (single-shot technique) could be an alternative approach to achieve PVI,

while avoiding unnecessary energy application at the PV ostium.

METHODS A total of 61 consecutive paroxysmal atrial fibrillation patients (age 64.1 � 10.9 years, 48 male) who

underwent antrum RHB-PVI were enrolled. Energy applications were performed following the pre-specified protocol only

targeting the PV antrum. If the PVI was not achieved after 2 energy applications using the RHB, a touch-up ablation was

performed.

RESULTS Of 241 PV, including 3 left common PV, 194 (80%) were isolated exclusively using the RHB. The target PVI

average per group of 15 consecutive procedures improved from 75% (initial 15) to 89% (last 16) of patients. The injected

volume was greatest in the right superior PV (13.1 � 2.0 ml) and the smallest in the left inferior PV (10.8 � 1.1 ml), and 23

PV (9.5%) required over 15 ml (estimated balloon diameter of 30 mm). Periprocedural complications were noted in 3

patients (4.9%), but phrenic nerve injury was not observed. Sinus rhythm maintenance at 12-month follow-up was

achieved in 57 patients (93%).

CONCLUSIONS A novel simplified antrum RHB-PVI appears to be a feasible technique for the treatment of paroxysmal

atrial fibrillation. (J Am Coll Cardiol EP 2019;5:354–63) © 2019 by the American College of Cardiology Foundation.

R adiofrequency hot-balloon catheter (RHB)(SATAKE Hot-Balloon, Toray Industries,Inc., Tokyo, Japan) consists of a high

compliant size-adjustable balloon (diameter 25 to 33mm) that helps to achieve better contact withirregular-shaped pulmonary vein (PV) ostia and cre-ates contiguous and transmural lesions (1). The

N 2405-500X/$36.00

m the Department of Cardiology, Faculty of Medicine, University of T

eived a consultant fee from Toray Industries, Inc. Dr. Aonuma has re

partment of Toray Industries, Inc. All other authors have reported that th

s paper to disclose.

authors attest they are in compliance with human studies committees

tutions and Food and Drug Administration guidelines, including patient co

JACC: Clinical Electrophysiology author instructions page.

nuscript received July 30, 2018; revised manuscript received January 15,

feasibility of the pulmonary vein isolation (PVI) usingthe radiofrequency hot-balloon catheter (RHB-PVI)has been proven in a randomized study (2). Duringthe clinical trial, the central balloon temperatureand radiofrequency energy delivery time was deter-mined empirically, and energy applications wereroutinely performed not only at the antrum, but also

https://doi.org/10.1016/j.jacep.2019.01.017

sukuba, Tsukuba, Ibaraki, Japan. Dr. Yamasaki has

ceived a grant from and belongs to the endowed

ey have no relationships relevant to the contents of

and animal welfare regulations of the authors’ in-

nsent where appropriate. For more information, visit

2019, accepted January 17, 2019.

AB BR E V I A T I O N S

AND ACRONYM S

IRQ = interquartile range

LIPV = left inferior pulmonary

vein

LSPV = left superior

pulmonary vein

PNI = phrenic nerve injury

PV = pulmonary vein

PVI = pulmonary vein isolation

PVS = pulmonary vein stenosis

RHB = radiofrequency hot-

balloon

RIPV = right inferior

pulmonary vein

RSPV = right superior

pulmonary vein

SVC = superior vena cava

TSP = transseptal puncture

J A C C : C L I N I C A L E L E C T R O P H Y S I O L O G Y V O L . 5 , N O . 3 , 2 0 1 9 Yamasaki et al.M A R C H 2 0 1 9 : 3 5 4 – 6 3 RHB Catheter Ablation

355

at the ostium and carina (3). As a result, acute com-plete PVI was achieved in 98% of the PV. However,phrenic nerve injury (PNI) and severe PV stenosis(PVS; >70%) were observed in total of 8.9% of the pa-tients with a smaller injection volume (<10 ml). Espe-cially, the incidence of severe PVS of 5.2% wassignificantly higher compared to that with the otherballoon technologies (4,5). In addition, asymptomaticbut moderate PVS (50% to 70%) was found in 22.4% ofthe patients (6). Energy application at the PV ostiumincreases the risk of collateral damage; thus, estab-lishment of an alternative approach was stronglydesired.

Based on the RHB principle, longer energy appli-cation creates a deeper lesion (1). We hypothesizedthat a longer energy application targeting the PVantrum with larger injection volume could be analternative approach to achieve PVI, while avoidingunnecessary energy application at the PV ostium.Accordingly, we developed a novel simplified RHB-PVI protocol targeting only the PV antrum (single-shot technique). In this study, we aim to elucidate thefeasibility of the simplified technique, its efficacy,and the safety profile.

METHODS

STUDY POPULATION. This is a retrospective single-center study to evaluate the feasibility of the simpli-fied ablation protocol targeting only the PV antrum.After the approval of the RHB system in April 2016,108 patients underwent RHB-PVI at the TsukubaUniversity Hospital from April 1, 2016, to March 31,2017. Initially, 10 patients were treated with an abla-tion protocol used during the clinical trial. Then, webegan to adopt the simplified technique targetingonly the PV antrum (single-shot technique). In thisretrospective analysis, a total of 61 consecutive pa-tients, with a history of paroxysmal atrial fibrillationwere included. Patients with a history of persistentatrial fibrillation (n ¼ 28), structural heart disease(n ¼ 3), chronic renal failure on dialysis (n ¼ 2), andfollow-up period <6 months (n ¼ 4) were excluded.Pre-procedural imaging was not mandatory andantrum RHB-PVI was performed irrespective of thePV variants. As a result, patients with left long com-mon PV (n ¼ 3) were included. All antiarrhythmicdrugs were discontinued at least 5 half-lives beforethe procedure. At the beginning, only 1 surgeon (H.Y.)performed the procedure. From September 2016, 5fellows of electrophysiology (Y.S., Y.K., K.M., N.H.,E.S.) performed the ablations. In those cases, themost experienced doctor in the team (H.Y.) gave thefinal decision on the injected volume and the balloon

position. All patients provided their writteninformed consent before the procedure. Thestudy protocol was approved by the ethicscommittee of the Tsukuba UniversityHospital.

ABLATION PROTOCOL. The procedure wasperformed under conscious sedation usingdexmedetomidine and fentanyl. After groinpunctures, 5,000 units of heparin were given.A steerable mapping catheter (Bee AT, JapanLifeline Co., Ltd., Tokyo, Japan) was posi-tioned within the coronary sinus. A 10-polarmapping catheter (Inquiry Steerable Diag-nostic Catheter; Abbott, St. Paul, Minnesota)was positioned at the His-bundle area and apig-tail catheter was placed at the non-coronary cusp as a landmark for the trans-septal puncture (TSP).

Double TSP were performed using a radi-

ofrequency needle (NRG RF Transseptal Needle,Baylis Medical, Montreal, Quebec) and 8-F longsheath (SL0; Abbott) under fluoroscopic guidance.After the initial TSP, a guidewire was advanced intothe left superior pulmonary vein (LSPV) and thecourse of the guidewire was confirmed in the rightanterior oblique projection. If the guidewire wasadvanced into the LSPV in a coaxial position, thesecond TSP was attempted slightly anterior to theinitial TSP site. If the advanced first guidewire failedto achieve coaxial position to the LSPV, the secondTSP was attempted slightly posterior to the initial TSPsite to achieve better coaxial position (Figure 1). Thebolus heparin was given immediately after the initialTSP followed by continuous heparin to achieve thetarget activated clotting time between 300 and 350 s.

A direct PV angiogram was performed to visualizethe left atrium–PV junction location and PV branches.An oral airway was inserted to prevent deep respira-tion during the sedation, and an esophageal ther-mometer (Esophaster, Japan Lifeline Co.,Ltd.) wasinserted for continuous esophageal temperaturemonitoring.

The 8-F long sheath crossing the atrial septumposteriorly was exchanged over a J-tip guidewire(Spring Guide Wire, Toray Medical Co., Ltd., Tokyo,Japan) for a 17-F deflectable guiding sheath (Tres-waltz, Toray Industries, Inc.). The balloon was grad-ually inflated with target injection volume of $10 ml(estimated diameter of 25 mm) of contrast mediumdiluted 1:1 with normal saline in the PV. The curve ofthe deflectable guiding sheath was adjusted and thecoaxial position of the RHB to the PV antrum wasconfirmed by the 2 different fluoroscopy angles

FIGURE 1 Fluoroscopic Guided Double Transseptal Puncture

(A) After an initial transseptal puncture (TSP) (white asterisk), a course of the guidewire (dotted line) was checked in the right anterior oblique projection (RAO) (left

panel). If the coaxial position of the guidewire to the left superior pulmonary vein was not achieved, a second TSP (red asterisk) was attempted more posterior to the

initial TSP site (middle panel). A better coaxial position of the guidewire (dotted line) to the left superior pulmonary vein was achieved using the second TSP site (right

panel). (B) Anatomical schema describing the relationship between TSP sites and pulmonary veins in RAO projection (left panel) and superior projection (middle and

right panels). Posterior TSP site, compared with the anterior TSP site, enabled the operator to achieve better coaxial position to the left and right pulmonary veins.

Yamasaki et al. J A C C : C L I N I C A L E L E C T R O P H Y S I O L O G Y V O L . 5 , N O . 3 , 2 0 1 9

RHB Catheter Ablation M A R C H 2 0 1 9 : 3 5 4 – 6 3

356

(Figure 2). Along with balloon inflation, the balloonwas gradually moved toward the antrum. Using thepre-acquired PV angiogram results as a reference,careful attention was paid to maintain a coaxial po-sition with forward pressure in order to avoid“popping out” from the PV antrum. The largest in-jection volume with complete occlusion wasconfirmed with a selective PV angiogram andconsidered as the optimal balloon size. The energyapplication was delivered as follows: right superiorpulmonary vein (RSPV) (70�C, 3.5 min), right inferiorpulmonary vein (RIP) (70�C, 3 min), left inferior pul-monary vein (LIPV) (70�C, 2.0 to 2.5 min), and LSPV(70�C, 4 min) (Central Illustration). To prevent PNI,

pacing was applied from an electrode in the superiorvena cava (SVC) during energy applications in theright PV. After each energy application, a circularmapping catheter was placed in the PV. If the PVpotential remained, a second energy application wasconsidered. In such cases, the guidewire was insertedinto a different PV branch (Online Figure 1) to enablebetter contact with the remaining conduction site. Atouch-up ablation with an irrigated ablation catheter(FlexAbility; Abbott) was performed if the PV con-duction remained after a maximum of 2 energy ap-plications or reconduction was observedspontaneously. A voltage map using 3-dimensionalmapping system was obtained to confirm the

FIGURE 2 Selective Pulmonary Vein Angiogram

Representative selective pulmonary angiograms of the left inferior pulmonary vein (A) and right inferior pulmonary vein (B). Coaxial position of the balloon to the target

vein (white dotted line) was achieved by adjusting the curve of the deflectable sheath and was confirmed by 2 different fluoroscopy angles. Deformation of the balloon

(white arrowheads) provides a visual understanding that the compliant balloon was firmly pushed against the pulmonary vein antrum. LAO ¼ left anterior oblique;

RAO ¼ right anterior oblique.

J A C C : C L I N I C A L E L E C T R O P H Y S I O L O G Y V O L . 5 , N O . 3 , 2 0 1 9 Yamasaki et al.M A R C H 2 0 1 9 : 3 5 4 – 6 3 RHB Catheter Ablation

357

isolation area. Then, PV reconnection was tested us-ing isoproterenol (1 mg/min) and adenosine triphos-phate (20 mg) and touch-up ablation was performed ifnecessary. If the patient had a history or inducibleatrial flutter, cavotricuspid isthmus ablation wasperformed. Isolation of the SVC was also performed atthe physician’s discretion. Ablation time and totalenergy application only included energy applicationsusing the RHB and the procedure time was calculatedfrom the time of TSP to the time of protamineadministration after ablation (2).

ESOPHAGEAL TEMPERATURE MONITORING AND

ENDOSCOPY EVALUATION. To avoid esophagealinjury, cooling water (0�C) was injected into theesophagus (initial injection with 10 ml; repeated with5 ml of injection bolus) when the esophageal tem-perature exceeded 39�C (7). If the rapid temperaturefall was not observed immediately after the coolingwater injection, the guiding sheath was slightlyturned counterclockwise while maintaining the for-ward pressure. This maneuver helped to providespace for the cooling water to pass through theesophagus behind the balloon. If the temperatureincreased over 39�C in every 30 s, it was considered tobe frequent and the energy application was shortenedfrom 2.5 min to 2 min during the LIPV ablation.

Endoscopic examination was scheduled as a part ofthe post-procedural assessment to evaluate the inci-dence of esophagus-related injury regardless of thesymptom. Esophagus-related injury was defined asany injury resulting from energy applications,including esophageal erythema, necrotic ulcerations,atrio-esophageal fistulae, acute pyloric spasms, andgastric hypomotility (8). The endoscopy was per-formed and assessed by independent, experiencedgastroenterologists blinded to the patients’ clinicaldata within 48 h after the index procedure.

FOLLOW-UP. No antiarrhythmic drugs were pre-scribed after the procedure. If the patient had animmediate recurrence within a blanking period,antiarrhythmic drugs were prescribed at the physi-cian’s discretion and stopped at 3 months. Follow-upvisits consisted of a clinical interview, electrocardio-grams, and 24-h Holter monitoring at 3, 6, and 12months. Recurrence was defined as any atrial tachy-arrhythmia lasting longer than 30 s, and a 3-monthblanking period was applied.

STATISTICAL ANALYSIS. Continuous data areexpressed as mean � SD for normally distributedvariables or as median (interquartile range [IQR]) fornon-normally distributed variables. Acute successwas defined by PVI achieved only using the RHB.

CENTRAL ILLUSTRATION Pulmonary Vein Antrum Isolation With Single-Shot Technique

Yamasaki, H. et al. J Am Coll Cardiol EP. 2019;5(3):354–63.

(A) Schema and representative fluoroscopy views of the simplified ablation protocol. The target central temperature and the energy duration are described in the figure.

(B) A voltage mapping after the energy applications in the same patient. AP ¼ anterior-posterior; LAO ¼ left anterior oblique; LIPV ¼ left inferior pulmonary vein;

LSPV ¼ left superior pulmonary vein; PA ¼ posterior-anterior; RAO ¼ right anterior oblique; RIPV ¼ right inferior pulmonary vein; RSPV ¼ right superior pulmonary vein.

Yamasaki et al. J A C C : C L I N I C A L E L E C T R O P H Y S I O L O G Y V O L . 5 , N O . 3 , 2 0 1 9

RHB Catheter Ablation M A R C H 2 0 1 9 : 3 5 4 – 6 3

358

The learning curve was analyzed in blocks of 15 pa-tients (the last group included 16 patients) and pro-cedure time was compared using the 1-way analysis ofvariance. A Kaplan-Meier curve was plotted for thetime to first atrial arrhythmia recurrence if any. Aprobability value of p < 0.05 indicated statisticalsignificance.

RESULTS

PATIENT AND PROCEDURAL CHARACTERISTICS.

Patient and procedural characteristics are shown inTable 1. A total of 61 patients (48 male, 64.1 � 10.9years), underwent antrum RHB-PVI using the

single-shot technique. The mean left atrial dimensionand left atrial volume index was 36.9 � 4.8 mm and33.7 � 12.6 ml/m2, respectively. Pre-procedural im-aging was acquired using multidetector computedtomography in 38 patients (62%).

As shown in Table 2, energy applications per pro-cedure were 5.2 � 1.0. The injected volume wasgreatest in the RSPV (13.1 � 2.0 ml) and smallest in theLIPV (10.8 � 1.1 ml), and over 15 ml (estimated balloondiameter of 30 mm) was required during the RSPVablations in 16 patients (26%), LSPV ablation in 3(4.9%), and RIPV ablation in 1 (1.6%). In 2 patientswith left common PV, successful isolation was ach-ieved with injection volumes of 20 ml and 17 ml,

TABLE 1 Baseline Patient Characteristics (N ¼ 61)

Age, yrs 64.1 � 10.9

Male 48 (79.0)

BMI, kg/m2 24.2 � 3.1

LA diameter, mm 36.9 � 4.8

LA volume index, ml/m2 33.7 � 12.6

LVEF, % 67.1 � 6.5

Pre-procedural imaging 38 (62.0)

Hypertension 40 (66.0)

CHA2DS2-VASc score

0 11 (18.0)

1 14 (23.0)

2 23 (37.7)

3 8 (13.1)

4 2 (3.3)

5 2 (3.3)

6 1 (1.6)

Values are mean � SD or n (%).

BMI ¼ body mass index; CHA2DS2-VASc ¼ Congestive Heart Failure, Hyper-tension, Age $75 Years, Diabetes Mellitus, Prior Stroke or Transient IschemicAttack or Thromboembolism, Vascular Disease, Age 65 to 74 Years, Sex; LA ¼ leftatrium; LVEF ¼ left ventricular ejection fraction.

J A C C : C L I N I C A L E L E C T R O P H Y S I O L O G Y V O L . 5 , N O . 3 , 2 0 1 9 Yamasaki et al.M A R C H 2 0 1 9 : 3 5 4 – 6 3 RHB Catheter Ablation

359

respectively. Acute PVI was achieved using the RHBin 200 of 241 PV (83%) and 31 patients (51%). Duringthe procedure, spontaneous reconductions wereobserved in 6 PV (LSPV; n ¼ 2, RSPV; n ¼ 1, RIPV; n ¼3). As a result, 194 PV (80%) and 29 patients (49%)were isolated exclusively using the RHB. Touch-upablations were required in 41%, 5%, 16%, and 10% ofLSPV, LIPV, RSPV, and RIPV, respectively. Amongthose 47 PV requiring touch-up ablation, a single gapwas observed in 42 (89%) and most of the sites (83%)were found at the anterior bottom part of the PVwhere stable contact of the balloon against the PV

TABLE 2 Details of the Procedural Parameters (N ¼ 61)

Total ablation time* 16.1 � 2.4

Total energy application* 5.2 � 1.0

Ablation time per PV, min

Right superior 4.4 � 1.4

Right inferior 3.4 � 1.2

Left superior 5.5 � 1.6

Left inferior 2.9 � 0.7

Injection volume per PV, ml

Right superior 13.1 � 2.0

Right inferior 11.0 � 1.4

Left superior 12.5 � 2.0

Left inferior 10.8 � 1.1

Procedure time, min 83.1 � 18.6

Superior vena cava isolation 5 (8.2)

Atrial flutter ablation 12 (20.0)

Values are mean � SD or n (%). *Ablation time and total energy application onlyincluded energy applications using the radiofrequency hot-balloon catheter.

PV ¼ pulmonary vein.

antrum was difficult during exhalation or coaxialposition of the balloon to the PV was difficult toachieve. Among 159 PV of 40 patients (including 1patient with a left common PV), administration ofisoproterenol and adenosine provoked PV reconnec-tion in 2 PV (1.3%) where touch-up ablation wasrequired, whereas PV reconnection was not observedafter successful antrum RHB-PVI. The average pro-cedure time was 83.1 � 13.6 min. In addition to thePVI, SVC isolation and right atrial isthmus ablationwere performed in 5 patients (8.2%) and 12 patients(20%), respectively.

ANALYSIS OF THE LEARNING CURVE. The learningcurve of the procedure was evaluated by comparingthe procedural results in groups of 15 patients. Theacute success rate per PV was significantly improvedfrom 75% in the initial group to 89% in the last group(p < 0.05), and was apparent in LIPV and RSPV(Figure 3, Online Figure 2). Also, the procedure timereduced from 89 � 16 to 74 � 14 min (<0.05). Thenumber of procedures performed by each physicianwere 41 (H.Y.), 10 (Y.S.), 5 (Y.K.), 3 (K.M.), and 1 each(N.H. and E.S.). Accordingly, new surgeons performed42% of the procedure after 5 months.

ACUTE COMPLICATION. In this series, there were 3complications (1 pseudo-aneurysm, 2 cardiac tampo-nades) (Table 3). In 1 patient, cardiac tamponadedeveloped shortly after inadvertent body movementand mechanical trauma from a catheter placed at theright ventricular apex was suspected. In another case,perforation of the left atrial appendage due to theguidewire was observed (9). In each patient, peri-cardiocentesis stabilized the hemodynamic condi-tion. No patient experienced PNI and none requiredimmediate termination of the energy application dueto suspected PNI.

ENDOSCOPY EVALUATION. During the procedure,cooling saline was injected for a median of 6 times(IQR: 3.5 to 8.5) with median of 35 ml (IQR: 22.5 to47.5). Among 61 patients, 54 (89%) underwent endo-scopic evaluation. Asymptomatic esophageal ery-thema and gastric hypomotility were found in 3(5.6%) and 4 patients (6.6%), respectively. There wasno esophageal ulceration, atrio-esophageal fistula, orpyloric spasm (Table 3). In addition, there was noclinically relevant aspiration pneumonia related tothe cooling saline injection.

CLINICAL OUTCOME. Patients were followed-up for amedian of 398 (IQR: 369 to 563) days and recurrenceof any type of atrial arrhythmia was observed in 9patients (14.8%). There was no post-proceduraldeath. The Kaplan-Meier plot with event-free

FIGURE 3 Learning Curve of the Procedure

(A) A learning curve of the acute success rate per patient (black bars) per pulmonary vein (gray bars). (B) A learning curve of the procedure time.

Yamasaki et al. J A C C : C L I N I C A L E L E C T R O P H Y S I O L O G Y V O L . 5 , N O . 3 , 2 0 1 9

RHB Catheter Ablation M A R C H 2 0 1 9 : 3 5 4 – 6 3

360

survival is presented in Figure 4. At 12 months, thedrug-free rate of freedom from any atrial arrhythmiawas 93%. Six patients underwent a repeat ablation atmedian of 464 (IQR: 386 to 517) days after the initialprocedure. Among them, PV reconduction wasobserved in 6 of 24 PV (25%).

TABLE 3 Details of the Periprocedural Complication (N ¼ 61)

Cardiac tamponade 2 (3.3)

Groin hematoma 0 (0.0)

Pseudo aneurysm 1 (1.6)

Phrenic nerve palsy 0 (0.0)

Stroke/transient ischemic attack 0 (0.0)

Endoscopy examination (n ¼ 54)

Esophagus erythema 3 (5.6)

Esophageal ulceration 0 (0.0)

Atrio-esophageal fistula 0 (0.0)

Gastric hypomotility 4 (6.6)

Pyloric spasm 0 (0.0)

Post-procedural MDCT (n ¼ 40) pulmonary vein stenosis

Severe, >70% 2 (5.0)

Moderate, 50% to 70% 0 (0.0)

Values are n (%).

MDCT ¼ multidetector computed tomography.

DISCUSSION

MAIN FINDINGS. This study provided several newfindings. First, a novel antrum RHB-PVI, with thesingle-shot technique, was found to be feasible andcould be performed with a short learning curve.Among 241 PV, 194 (80%) were exclusively isolatedusing the RHB-PVI. During the study period, acutesuccess rate per PV was significantly improved from75% to 89% when comparing the initial group to thelast group. Second, sinus rhythm was maintainedwithout antiarrhythmic drugs in 93% of the patientsat 12-month follow-up. Third, antrum PVI using thesize-adjustable RHB successfully avoided PNI irre-spective of the shape of the right PV ostium, whichremains a significant concern in other balloon-basedPVI (4,5).

ANTRUM RHB-PVI AS A SINGLE-SHOT DEVICE. Thisis the first study to describe the detailed technique ofthe simplified antrum RHB-PVI and evaluate itsfeasibility for treatment of paroxysmal atrial fibrilla-tion. By adjusting the injection volume while main-taining a coaxial position and forward pressure, RHB

FIGURE 4 Outcome After Pulmonary Vein Antrum Isolation

A Kaplan-Meier curve of the freedom from arrhythmia recurrence of antiarrhythmic drugs

after a single procedure.

J A C C : C L I N I C A L E L E C T R O P H Y S I O L O G Y V O L . 5 , N O . 3 , 2 0 1 9 Yamasaki et al.M A R C H 2 0 1 9 : 3 5 4 – 6 3 RHB Catheter Ablation

361

enabled the achievement of complete PV occlusion atthe level of the PV antrum and successfully isolatedPV by prolonging energy application. During the RHBrandomized trial, energy applications were deliveredat the ostium, antrum, and carina. The injection vol-ume (average injection volume at the PV antrum andostium) was greatest at the LSPV (10.2 � 2.9 ml) andsmallest at the RIPV (7.9 � 1.8 ml). A smaller injectionvolume resulted in a high PV isolation rate (98%) (2)but increased the risk of severe PV stenosis and PNI.During this study, 9.5% of the PV including leftcommon PV, required injected volume over 15 ml(estimated diameter of 30 mm). Although furtherstudy is required to establish the optimal energysetting, the unique feature of the size-adjustable RHBenables its use as a single-shot device to create acontiguous lesion at the level of PV antrum irre-spective of the PV anatomy.

LEARNING CURVE OF THE ANTRUM RHB-PVI. In thisstudy, the result clearly showed a learning curve andacute PVI was achieved in 89%, exclusively using theRHB in the last group. Surprisingly, the success rate,as well as procedure time, was not affected by newsurgeons. This finding was contrary to that of thecryoballoon. In the STOP-AF (Sustained Treatment ofParoxysmal Atrial Fibrillation) trial, the success andcomplication rates were affected by the number ofprocedures. In the study, doctors who had performed12 to 23 procedures had a success rate of 90%, and forthose who had performed only 1 or 2 cases, the suc-cess rate was 56% (10). We speculated that a defor-mation of the high-compliant balloon provided avisual understanding of the balloon position at the PVantrum. The visual feedback helped to adjust the in-jection volume and catheter manipulation to achievebetter PV occlusion throughout energy applications;thereby new surgeons could achieve similar resultswith advice from the experienced doctor.

CHRONIC SUCCESS RATE AFTER THE ANTRUM

RHB-PVI. At the 12-month follow-up, sinus rhythmwas maintained in 93% of the patients. The antrumRHB-PVI, with greater injection volume, suggestedthat the balloon was attached to a more proximal areaof the PV antrum and an isolated wider area thanthose of the randomized study. Although touch-upablations were required in 20% of the PV in thisstudy, most of the PV needed a single energy appli-cation to complete the PVI. This implied that contig-uous lesions were mostly achieved using the RHB atthe PV antrum. The number of patients requiring asecond ablation was limited, but durability of the PVisolation was 75% in those patients over 1 year after

the procedure and was similar to the cryoballoonablation (11).

Previous observational studies using the second-generation cryoballoon and laser balloon haddemonstrated arrhythmia-free survival of 83.6% and60.2% after 1 year (12,13), respectively. Though therewere some differences in the follow-up protocol andadditional ablation, it appeared that the result of thecurrent study was at least comparable or might bebetter. We speculated that antrum RHB-PVI success-fully avoiding PNI suggested a wider isolation areacompared with that of other balloon technologies andcontributed to a better clinical outcome.

COMPLICATIONS RELATED TO THE ANTRUM

RHB-PVI. PNI is a serious complication during anenergy application in the right-sided PV. The inci-dence of PNI after cryoballoon had been reported tobe significantly higher than that after radiofrequencycatheter ablation (14). In the Fire and Ice trial, PNIwas still observed (2.7%) even if patients with PVdiameter of >26 mm in the right side were excluded(8). Size-adjustable RHB was expected to be appli-cable in variable PV anatomies. Therefore, we havenot considered any anatomical exclusion criteria. Inthis study, the injection volume was greatest (13.1 �2.0 ml) during the RSPV isolation and 26% of theRSPV required an injection volume of >15 ml, whichsuccessfully prevented PNI. This observation stronglysuggested that the simplified antrum RHB-PVI

PERSPECTIVES

COMPETENCY IN MEDICAL KNOWLEDGE:

Antrum PVI using the size-adjustable RHB catheter

with avoidance of PNI is a feasible therapeutic option

of paroxysmal atrial fibrillation.

TRANSLATIONAL OUTLOOK: Multicenter study

with a large number of patients and new operators

are needed to assess the feasibility, safety, and long-

term success rate of this novel simplified approach.

Yamasaki et al. J A C C : C L I N I C A L E L E C T R O P H Y S I O L O G Y V O L . 5 , N O . 3 , 2 0 1 9

RHB Catheter Ablation M A R C H 2 0 1 9 : 3 5 4 – 6 3

362

protocol created a contiguous lesion in a more prox-imal area than the cryoballoon.

The esophageal-related injury is also anotherconcern. In this study, asymptomatic esophageal er-ythema and gastric hypomotility were found in 7 pa-tients (12.2%). A previous study had reported a higherincidence of esophageal-related injury (32.5%) aftersecond-generation cryoballoon ablation (15). Coolsaline injection and time adjustment in patients withfrequent esophageal temperature rise effectivelyprevented esophageal-related injuries. In addition,counterclockwise catheter manipulation in case offrequent esophageal temperature rise may haveavoided overheating of the posterior wall whilemaintaining good contact against the thicker anteriorridge.

STUDY LIMITATIONS. The present study described asingle-center retrospective experience with a smallnumber of patients reporting the initial experience ofantrum RHB-PVI. The follow-up duration was limitedand protocol was not as strict and neither telemetrynor 7-day Holter electrocardiogram were used. Sec-ond, 5 patients received SVC isolation per the physi-cian’s decision. Empirical SVC isolation had beenshown to improve the sinus rhythm maintenance;thereby it may have contributed to greater long-termsuccess (16). Third, the semiquantitative analysis ofPVS was not performed systematically. Post-procedural multidetector computed tomography wasperformed in 40 patients, and severe PVS wasobserved in 2 patients (5%) (Table 3). Of note, therewere no cases of moderate PVS. Both cases of severePVS occurred at the beginning of the procedure, andRHB may have been pushed inside the PV ostiumdespite the balloon being inflated by at least 15 ml.Our study showed a significant reduction of themoderate PVS as compared to the randomized clinicalstudy (6), but further study is needed to assess theimpact of antrum RHB-PVI on the post-procedural

severe PVS. Finally, we adopted a fixed ablationprotocol. Animal studies had shown that higher sur-face temperature of the balloon and longer energyapplication time are associated with deeper lesions(1). Larger injection volume had a negative correla-tion with the surface balloon temperature; thus, itwould decrease if the balloon was inflated withgreater injection volume. Therefore, longer energyapplication may be required to create a transmurallesion if the balloon was inflated with greater injec-tion volume. Further studies are necessary to deter-mine the optimal ablation protocol needed toimprove the acute success rate of RHB-PVI.

CONCLUSIONS

A novel simplified approach to achieve antrum RHB-PVI appeared to be feasible with a short learningcurve. Antrum RHB-PVI with avoidance of PNI ap-pears a feasible therapeutic option for the treatmentof paroxysmal atrial fibrillation.

ADDRESS FOR CORRESPONDENCE: Dr. Hiro Yamasaki,Department of Cardiology, Faculty of Medicine,University of Tsukuba, 1-1-1 Tennodai, Tsukuba305-8575, Japan. E-mail: hyamasaki@md.tsukuba.ac.jp.

RE F E RENCE S

1. Evonich RF, Nori DM, Haines DE. Efficacy ofpulmonary vein isolation with a novel hot balloonablation catheter. J Interv Card Electrophysiol2012;34:29–36.

2. Sohara H, Ohe T, Okumura K, et al. HotBalloonablation of the pulmonary veins for paroxysmalAF: a multicenter randomized trial in Japan. J AmColl Cardiol 2016;68:2747–57.

3. Sohara H. Radiofrequency HotBalloon ablationcatheter. In: Kenzo H, editor. Ablation: A CurrentApproach on Cardiac Arrhythmias. Singapore:Springer, 2018:157–68.

4. Kuck KH, Brugada J, Fürnkranz A, et al. Cry-oballoon or radiofrequency ablation for parox-ysmal atrial fibrillation. N Engl J Med 2016;374:2235–45.

5. Dukkipati SR, Cuoco F, Kutinsky I, et al. Pul-monary Vein isolation using the visually guidedlaser balloon: a prospective, multicenter, andrandomized comparison to standard radio-frequency ablation. J Am Coll Cardiol 2015;66:1350–60.

6. Applications for Manufacturing/MarketingApproval for Medical Devices (in Japanese). PMDA

(Pharmaceuticals and Medical Devices Agency).Available at: http://www.pmda.go.jp/medical_devices/2015/M20151118001/index.html.Accessed February 21 2019.

7. Sohara H, Satake S, Takeda H, Yamaguchi Y,Nagasu N. Prevalence of esophageal ulcerationafter atrial fibrillation ablation with the hotballoon ablation catheter: what is the value ofesophageal cooling? J Cardiovasc Electrophysiol2014;25:686–92.

8. Yamasaki H, Tada H, Sekiguchi Y, et al. Preva-lence and characteristics of asymptomatic

J A C C : C L I N I C A L E L E C T R O P H Y S I O L O G Y V O L . 5 , N O . 3 , 2 0 1 9 Yamasaki et al.M A R C H 2 0 1 9 : 3 5 4 – 6 3 RHB Catheter Ablation

363

excessive transmural injury after radiofrequencycatheter ablation of atrial fibrillation. HeartRhythm 2011;8:826–32.

9. Yamasaki H, Yamagami F, Machino T, et al.Perforation of the left atrial appendage caused byinadvertent deployment of a soft J-tipped guide-wire during radiofrequency hot-balloon ablation.Circ J 2018;82:1476–7.

10. Bunch T. Cryoballoon ablation for atrial fibril-lation. Is it the right choice for my practice?J Innov Cardi Rhythm Manag 2011;2:272–3.

11. Aryana A, Mugnai G, Singh SM, et al. Proceduraland biophysical indicators of durable pulmonaryvein isolation during cryoballoon ablation of atrialfibrillation. Heart Rhythm 2016;13:424–32.

12. Fürnkranz A, Bordignon S, Dugo D, et al.Improved 1-year clinical success rate of pulmonary

vein isolation with the second-generation cry-oballoon in patients with paroxysmal atrial fibril-lation. J Cardiovasc Electrophysiol 2014;25:840–4.

13. Dukkipati SR, Kuck KH, Neuzil P, et al. Pul-monary vein isolation using a visually guided laserballoon catheter: the first 200-patient multicenterclinical experience. Circ Arrhythm Electrophysiol2013;6:467–72.

14. Buiatti A, von Olshausen G, Barthel P, et al.Cryoballoon vs. radiofrequency ablation forparoxysmal atrial fibrillation: an updated meta-analysis of randomized and observational studies.Europace 2017;19:378–84.

15. Miyazaki S, Nakamura H, Taniguchi H, et al.Esophagus-related complications during second-generation cryoballoon ablation-insight fromsimultaneous esophageal temperature monitoring

from 2 esophageal probes. J Cardiovasc Electro-physiol 2016;27:1038–44.

16. Li JY, Jiang JB, Zhong GQ, Ke HH, He Y.Comparison of empiric isolation and conventionalisolation of superior vena cava in addition to pul-monary vein isolation on the outcome of parox-ysmal atrial fibrillation ablation. Int Heart J 2017;58:500–5.

KEY WORDS antrum pulmonary veinisolation, learning curve, paroxysmal atrialfibrillation, phrenic nerve injury,radiofrequency hot-balloon ablation

APPENDIX For supplemental figures, pleasesee the online version of this paper.