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 Table of Contents  
ORIGINAL ARTICLE
Year : 2020  |  Volume : 5  |  Issue : 1  |  Page : 8-13

Comparison of radiofrequency ablation versus cryoballoon ablation for paroxysmal atrial fibrillation: A nonrandomized controlled study (English version)


Department of Cardiology, Nanjing Drum Tower Hospital, The Affiliated Hospital of Nanjing University Medical School, Nanjing, Jiangsu Province, China

Date of Submission31-Oct-2020
Date of Decision12-Nov-2020
Date of Acceptance17-Nov-2020
Date of Web Publication28-Jan-2021

Correspondence Address:
Donghui Ma
Department of Cardiology, Nanjing Drum Tower Hospital, The Affiliated Hospital of Nanjing University Medical School, Nanjing 210008, Jiangsu Province
China
Prof. Wei Xu
Department of Cardiology, Nanjing Drum Tower Hospital, The Affiliated Hospital of Nanjing University Medical School, Nanjing 210008, Jiangsu Province
China
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/IJHR.IJHR_10_20

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  Abstract 

Background: In recent years, catheter ablation has been widely used in the treatment of paroxysmal atrial fibrillation (AF). Radiofrequency ablation has long been standard of care, whereas cryoballoon ablation has emerged as a new alternative for the treatment of paroxysmal AF. The present study aims to investigate the efficacy and safety of radiofrequency ablation and cryoballoon ablation for paroxysmal AF. Subjects and Methods: This retrospective nonrandomized controlled study consecutively enrolled 582 patients with paroxysmal AF who underwent radiofrequency ablation or cryoballoon ablation for the first time in Nanjing Drum Tower Hospital from September 2014 to October 2018. The enrolled patients were divided into four groups according to the ablation energy source used and instruments: normal saline irrigation catheter group (Group A), contact force-sensing catheter group (Group B), first-generation cryoballoon group (Group C), and second-generation cryoballoon group (Group D). The procedure time, X-ray exposure time, procedural complications, and 1-year recurrence rate were observed. This study was approved by the Medical Ethics Committee of Nanjing Drum Tower Hospital, The Affiliated Hospital of Nanjing University Medical School, China (approval No. 2014-190-01) on August 6, 2014. Results: There were no significant differences in baseline patient characteristics among the four groups. There were significant differences in the procedure times among Groups A, B, C, and D (163.6 ± 49.3, 142.4 ± 40.5, 136.6 ± 30.4, and 114.6 ± 24.2 min, respectively; P < 0.01). Moreover, the significant difference also existed in the X-ray exposure times among Groups A, B, C, and D (22.2 ± 8.4, 13.6 ± 8.7, 31.5 ± 7.3, and 26.5 ± 8.5 min, respectively; P < 0.01). In terms of procedural complications, the incidence of phrenic nerve palsy in patients who underwent cryoballoon ablation in Groups C and D was significantly higher than that under radiofrequency ablation in Groups A and B (P < 0.05), and there were no significant differences in the incidence of other procedural complications. The 1-year recurrence rates of AF/atrial flutter/atrial tachycardia in Groups A, B, C, and D were 23.8%, 15.4%, 15.1%, and 11.6%, respectively. Among them, the recurrence rates in Groups B and D were significantly lower than that in Group A (P < 0.05). Conclusions: The efficacy of a contact force-sensing catheter or second-generation cryoballoon in the treatment of paroxysmal AF is better than that of normal saline irrigation catheter. Both radiofrequency ablation and cryoballoon ablation are safe, and phrenic nerve palsy is a complication that requires special attention for cryoballoon ablation.

Keywords: Atrial fibrillation, cryoballoon ablation, pulmonary vein isolation, radiofrequency ablation


How to cite this article:
Bai J, Wang S, Zheng J, Li X, Chen Z, Sheng W, Liu Y, Gu R, Ma D, Xu W. Comparison of radiofrequency ablation versus cryoballoon ablation for paroxysmal atrial fibrillation: A nonrandomized controlled study (English version). Int J Heart Rhythm 2020;5:8-13

How to cite this URL:
Bai J, Wang S, Zheng J, Li X, Chen Z, Sheng W, Liu Y, Gu R, Ma D, Xu W. Comparison of radiofrequency ablation versus cryoballoon ablation for paroxysmal atrial fibrillation: A nonrandomized controlled study (English version). Int J Heart Rhythm [serial online] 2020 [cited 2021 Sep 24];5:8-13. Available from: https://www.ijhronline.org/text.asp?2020/5/1/8/308166

This manuscript is an English version based on Bai J, Wang X, Zheng J, Li X, Chen Z, Sheng W, et al. Efficacy of radiofrequency ablation and cryoballoon ablation for paroxysmal atrial fibrillation. Chin J Cardiac Arrhyth 2020;24(3):303-7. The second publication of this manuscript has obtained the permission from Chinese Journal of Cardiac Arrhythmias.


  Introduction Top


Atrial fibrillation (AF) is the most common arrhythmia and one of the main causes of stroke, which can endanger life and seriously affect the quality of life of the patients.[1] Since Haïssaguerre et al.[2] found that the abnormal electrical activity generated by ectopic excitation foci in the pulmonary veins was a major trigger for paroxysmal AF, pulmonary vein isolation has become the cornerstone of paroxysmal AF ablation. Traditionally, pulmonary vein isolation is performed with a “point-by-point” ablation technique by means of radiofrequency energy; however, in recent years, the use of novel alternative tools such as cryoballoon ablation is growing rapidly. Cryoballoon ablation uses a cryoballoon to be placed in the pulmonary vein ostia, which then delivers freezing energy to isolate the pulmonary veins circumferentially with a single application.[3] The two energy approaches of pulmonary vein isolation have shown the efficacy and safety in the treatment of paroxysmal AF, but which one has more advantages is still controversial. The aim of this study was to evaluate the efficacy and safety of cryoballoon ablation compared to radiofrequency ablation in patients with paroxysmal AF at our center.


  Subjects and Methods Top


Subjects

This retrospective nonrandomized controlled study consecutively enrolled 582 patients with paroxysmal AF who underwent radiofrequency ablation or cryoballoon ablation for the first time in Nanjing Drum Tower Hospital from September 2014 to October 2018. Inclusion criteria: patients who were diagnosed with symptomatic paroxysmal AF by electrocardiogram. Paroxysmal AF was defined as AF lasting <7 days with spontaneous termination.[4] Exclusion criteria were as follows: persistent fibrillation ablation, history of AF ablation, valvular AF, and hyperthyroidism-related AF. The enrolled patients were divided into four groups according to the ablation energy source used and instruments: normal saline irrigation catheter group (Group A, n = 206), contact force-sensing catheter group (Group B, n = 208), first-generation cryoballoon group (Group C, n = 73), and second-generation cryoballoon group (Group D, n = 95). This study was performed in line with the 2013 Revision of the Declaration of Helsinki and was approved by the Medical Ethics Committee of Nanjing Drum Tower Hospital, The Affiliated Hospital of Nanjing University Medical School, China (approval No. 2014-190-01) on August 6, 2014. The need for written informed consent was waived owing to the retrospective nature of the study.

Radiofrequency ablation procedure

All patients underwent transesophageal echocardiography to rule out left atrial thrombus formation before ablation. Radiofrequency ablation was performed as follows: a decapolar catheter was positioned in the coronary sinus from the femoral vein. Following double transseptal puncture guided by fluoroscopy, intravenous heparin was administered as a bolus with continuous infusion to maintain an activated clotting time of 250–350 s. A circular electrode catheter (Lasso, Biosense Webster, Inc., Diamond Bar, CA, USA) was inserted into the left atrium for recording pulmonary vein potentials. Then, a three-dimensional electroanatomical map of the left atrium was performed with the Carto 3 System (Biosense Webster, Inc., Diamond Bar, CA, USA). Radiofrequency ablation was performed with a normal saline irrigation catheter (ThermoCool NaviStar, Biosense Webster, Inc.) or a contact force sensing catheter (ThermoCool SmartTouch, Biosense Webster, Inc.). Power was limited to 30–35 W at anterior, superior, and inferior sites and 25 W at posterior sites, with a target temperature of 40–43°C. In addition, the targeted contact force during radiofrequency ablation applications was 10–25 g when using the contact force-sensing catheter. After the pulmonary vein isolation, isoproterenol-induced latent pulmonary vein conduction and nonpulmonary vein triggers were identified and ablated at the physician's discretion. Patients who remained in AF at the end of the procedure were electrically cardioverted back to sinus rhythm.

Cryoballoon ablation procedure

A 15-Fr steerable sheath (FlexCath, Medtronic, Inc., Minneapolis, MN, USA) was introduced into the left atrium after a single transseptal puncture. Then, the cryoballoon (Medtronic, Inc.) was introduced into the sheath, inflated, and advanced to the ostium of each pulmonary vein. Before cryoenergy delivery, the occlusion of each pulmonary vein was assessed by pulmonary vein angiography, and optimal vessel occlusion was deemed as total contrast retention with no backflow in the atrium. Ablation of pulmonary vein ostium was performed with at least two applications of cryoenergy, 2 × 240 s with the first-generation cryoballoon and 180 + 120 s with the second-generation cryoballoon. Additional applications could be used if deemed necessary. To avoid phrenic nerve palsy, continuous monitoring of the phrenic nerve during ablation of the right pulmonary veins was performed by pacing the right phrenic nerve with a quadripolar catheter in the superior vena cava. Patients who remained in AF at the end of cryoballoon ablation were electrically cardioverted back to sinus rhythm.

Postprocedural care and follow-up

Oral anticoagulation was continued for at least 2 months and all antiarrhythmic drugs were withdrawn at 3 months after ablation. Oral proton pump inhibitors were administered for 4 weeks to prevent esophageal complications. The first 3 months following the procedure were considered a blanking period and all episodes in this period were excluded from the analysis. All patients were followed for 1 year after the ablation procedure with clinical visits, a 12-lead electrocardiogram, and a 24-h ambulatory Holter monitor at 3, 6, and 12 months. Additional monitoring was performed in response to patient symptoms. After the blanking period, any documented episode of atrial tachyarrhythmias lasting >30 s was considered a recurrence.

Statistical analysis

Statistical analysis was performed using SPSS 17.0 software (SPSS, Chicago, IL, USA). All continuous variables are expressed as means with standard deviations and were compared using the one-way analysis of variance, followed by the least significant difference post hoc test. Categorical variables are expressed as numbers and percentages and were compared using the Pearson's Chi-square test or Fisher's exact test when appropriate. Time-to-event analysis was performed using Kaplan–Meier survival curves, utilizing the log-rank test to compare differences between the groups. All statistical tests were two-tailed, and P < 0.05 was considered significant.


  Results Top


Patient characteristics

A total of 582 patients finally completed 1-year follow-up, including 206 patients in Group A, 208 patients in Group B, 73 patients in Group C, and 95 patients in Group D [Figure 1]. Baseline characteristics (age, sex, body mass index, AF duration, left atrial size, ejection fraction, CHA2DS2-VASc and HAS-BLED scores (congestive heart failure, hypertension, age ≥75 [doubled], diabetes mellitus, prior stroke or transient ischemic attack [doubled], vascular disease, age 65–74, female), and underlying diseases) were not different among the four groups [Table 1].
Figure 1: Flow diagram of study patients. PAF = Paroxysmal atrial fibrillation, AF = Atrial fibrillation. Group A: Normal saline irrigation catheter group, Group B: Contact force-sensing catheter group, Group C: First-generation cryoballoon group, Group D: Second-generation cryoballoon group

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Table 1: Baseline clinical characteristics

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Comparison of procedural parameters

The procedure time was significantly longer in Group A compared with other groups (P < 0.01) and was significantly shorter in Group D compared with other groups (P < 0.01). There was no significant difference in the procedure times between Groups B and C [P = 0.293; [Table 2] and [Table 3].
Table 2: Procedural parameters and complications

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Table 3: Pairwise comparison (P values)

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The X-ray exposure time was significantly longer in Group C compared with other groups (P < 0.01) and was significantly shorter in Group B compared with other groups (P < 0.01). The X-ray exposure time of Group A was significantly shorter than Group D [P < 0.01; [Table 2] and [Table 3].

Comparison of procedural complications

All procedural complications are listed in [Table 2]. There was no significant difference in procedure-related death, ischemic stroke or transient ischemic attack, vascular complications, pericardial tamponade, pulmonary vein stenosis, and atrioesophageal fistula among the four groups (P > 0.05). As expected, phrenic nerve palsy was more frequent in cryoballoon ablation compared to radiofrequency ablation (P < 0.05). There was no phrenic nerve palsy in both Groups A and B; two patients in Group C had phrenic nerve palsy at discharge and one of them resolved before the 6-month follow-up; and one patient in Group D had phrenic nerve palsy at discharge and resolved before the 3-month follow-up.

One-year follow-up results

The recurrence rate was significantly higher in Group A (23.8% [49/206]) compared with Groups B (15.4% [32/208]) and D (11.6% [11/95], P < 0.05), but there was no significant difference between Groups A and C (15.1% [11/73], P = 0.116). In addition, there was no significant difference in the recurrence rate among Groups B, C, and D (P > 0.05). The atrial tachyarrhythmias-free survival curves for the four groups are reported in [Figure 2].
Figure 2: Atrial tachyarrhythmias-free survival curves for radiofrequency and cryoballoon ablation. AF = Atrial fibrillation, AFL = Atrial flutter, AT = Atrial tachycardia. Group A: Normal saline irrigation catheter group, Group B: Contact force-sensing catheter group, Group C: First-generation cryoballoon group, Group D: Second-generation cryoballoon group

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  Discussion Top


Currently, pulmonary vein isolation is a cornerstone ablation strategy in the management of patients with paroxysmal AF.[5],[6] This study followed up 582 patients with paroxysmal AF who underwent radiofrequency ablation or cryoballoon ablation for the first time in Nanjing Drum Tower Hospital, and the main findings are that (1) procedure time of cryoballoon ablation for paroxysmal AF was shorter than that of radiofrequency ablation; (2) X-ray exposure time of cryoballoon ablation for paroxysmal AF was longer than that of radiofrequency ablation; (3) procedural complications were similar in both cryoballoon and radiofrequency ablation with the exception of phrenic nerve palsy, which only occurred in the cryoballoon ablation groups; and (4) the 1-year recurrence rate of AF/atrial flutter/atrial tachycardia (AFL/AT) was significantly higher in Group A as compared with Groups B and D.

Radiofrequency ablation and cryoballoon ablation are the main procedures for pulmonary vein isolation, and in recent years, innovative tools such as the contact force-sensing catheter and second-generation cryoballoon have been introduced and have demonstrated their potential for safe and effective pulmonary vein isolation. Compared with the normal saline irrigation catheter, the contact force-sensing catheter can provide a real-time estimation of the contact force between the tip of the catheter and the target myocardium, which provides the operator with accurate quantitative assessment of tissue contact, improves the ablation efficiency, and reduces procedural complications.[7] In recent years, a number of clinical studies have indicated that the use of contact force-sensing catheter ablation has a lower recurrence rate of AF compared with normal saline irrigation catheters.[8],[9],[10] Compared with the first-generation cryoballoon, the second-generation cryoballoon was designed with technical modifications to create transmural contiguous lesions. The number of injection ports has been doubled from 4 to 8, and these have been positioned more distally on the catheter's shaft, resulting in a larger and more uniform zone of freezing on the balloon surface.[11] Many recent studies have shown that the second-generation cryoballoon has shorter procedure time and X-ray exposure time, and lower recurrence rate of AF compared with the first-generation cryoballoon.[12],[13],[14]

Fire and ice was the first large randomized controlled trial to compare the efficacy and safety of the cryoballoon ablation with the radiofrequency ablation in symptomatic patients with paroxysmal AF and showed noninferiority in efficacy and safety of cryoballoon versus radiofrequency ablation.[15] Another large multicenter clinical study reported that contact force-sensing catheter and second-generation cryoballoon have similar efficacy in the setting of paroxysmal AF ablation.[16] In this study, we also found that the 1-year recurrence rates of AF/AFL/AT were similar between contact force-sensing catheter and second-generation cryoballoon ablation, but both were superior to ablation using normal saline irrigation catheter. In recent years, many studies have reported that second-generation cryoballoon ablation has lower recurrence rate of AF/AFL/AT compared with the first-generation cryoballoon ablation.[13],[14],[17] However, in this study, we found that the 1-year recurrence rate of AF/AFL/AT was 15.1% and 11.6% in the first- and second-generation cryoballoon ablation groups, respectively, and the difference was not statistically significant. This may be related to the short follow-up time (only 1 year) and the relatively small number of patients in the two groups.

In our study, both radiofrequency ablation and cryoballoon ablation had fewer procedural complications, and the only difference between the two procedures was phrenic nerve palsy. No phrenic nerve palsy was observed in radiofrequency ablation groups. Phrenic nerve palsy is considered to be one of the most common complications of cryoballoon ablation. Previous studies suggested that 23 mm balloon is more likely to cause phrenic nerve palsy than 28 mm balloon, and the second-generation cryoballoon is more likely to cause phrenic nerve paralysis than the first-generation cryoballoon.[18],[20],[21] However, in our study, the incidence of phrenic nerve palsy in the first-and second-generation cryoballoon groups was 2.7% and 1.1%, respectively, with no significant difference between the two groups. Phrenic nerve injury is more likely to occur during cryoballoon ablation of the right pulmonary veins. In our center, phrenic nerve pacing is routinely performed during cryoballoon ablation of the right pulmonary veins, and once diaphragmatic weakness occurs, cryoballoon ablation is stopped immediately, thus avoiding further phrenic nerve palsy. In addition, a 28 mm balloon was used for all patients in our center for cryoballoon ablation, which was also helpful to reduce the occurrence of phrenic nerve palsy.

Limitations

The study presented here has two main limitations. First, it is a single-center retrospective study, and some biases exist due to the single-center study design. Second, the number of patients in cryoballoon ablation groups is relatively small and may have introduced bias in the interpretation of the results.


  Conclusions Top


Our preliminary findings suggest that the efficacy of using a contact force-sensing catheter or second-generation cryoballoon for paroxysmal AF is better than that of normal saline irrigation catheter. Both radiofrequency ablation and cryoballoon ablation are safe, and phrenic nerve palsy is a complication that requires special attention for cryoballoon ablation.

Institutional review board statement

This study was approved by the Medical Ethics Committee of Nanjing Drum Tower Hospital, The Affiliated Hospital of Nanjing University Medical School, China (approval No. 2014-190-01) on August 6, 2014.

Declaration of patient consent

The authors certify that they have obtained all appropriate consent from patients or their family members. In the forms, the patients or their family members have given their consent for the patients' images and other clinical information to be reported in the journal. The patients or their family members understand that the patients' names and initials will not be published and due efforts will be made to conceal the patients' identity forms.

Financial support and sponsorship

This work was supported by the National Natural Science Foundation of China (No. 81870291).

Conflicts of interest

There are no conflicts of interest.



 
  References Top

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Benjamin EJ, Wolf PA, D'Agostino RB, Silbershatz H, Kannel WB, Levy D. Impact of atrial fibrillation on the risk of death: The Framingham heart study. Circulation 1998;98:946-52.  Back to cited text no. 1
    
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Haïssaguerre M, Jaïs P, Shah DC, Takahashi A, Hocini M, Quiniou G, et al. Spontaneous initiation of atrial fibrillation by ectopic beats originating in the pulmonary veins. N Engl J Med 1998;339:659-66.  Back to cited text no. 2
    
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Andrade JG, Dubuc M, Guerra PG, Macle L, Mondésert B, Rivard L, et al. The biophysics and biomechanics of cryoballoon ablation. Pacing Clin Electrophysiol 2012;35:1162-8.  Back to cited text no. 3
    
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Schmidt M, Dorwarth U, Andresen D, Brachmann J, Kuck KH, Kuniss M, et al. Cryoballoon versus RF ablation in paroxysmal atrial fibrillation: Results from the German Ablation Registry. J Cardiovasc Electrophysiol 2014;25:1-7.  Back to cited text no. 4
    
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Calkins H, Kuck KH, Cappato R, Brugada J, Camm AJ, Chen SA, et al. 2012 HRS/EHRA/ECAS Expert consensus statement on catheter and surgical ablation of atrial fibrillation: Recommendations for patient selection, procedural techniques, patient management and follow-up, definitions, Endpoints, and Res Trial Design. Europace 2012;14:528-606.  Back to cited text no. 5
    
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Andrade JG, Monir G, Pollak SJ, Khairy P, Dubuc M, Roy D, et al. Pulmonary vein isolation using “contact force” ablation: The effect on dormant conduction and long-term freedom from recurrent atrial fibrillation-a prospective study. Heart Rhythm 2014;11:1919-24.  Back to cited text no. 8
    
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Hussein AA, Barakat AF, Saliba WI, Tarakji KG, Bassiouny M, Baranowski B, et al. Persistent atrial fibrillation ablation with or without contact force sensing. J Cardiovasc Electrophysiol 2017;28:483-8.  Back to cited text no. 9
    
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Iacopino S, Mugnai G, Takarada K, Paparella G, Ströker E, De Regibus V, et al. Second-generation cryoballoon ablation without the use of real-time recordings: A novel strategy based on a temperature-guided approach to ablation. Heart Rhythm 2017;14:322-8.  Back to cited text no. 11
    
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Giovanni GD, Wauters K, Chierchia GB, Sieira J, Levinstein M, Conte G, et al. One-year follow-up after single procedure Cryoballoon ablation: A comparison between the first and second generation balloon. J Cardiovasc Electrophysiol 2014;25:834-9.  Back to cited text no. 13
    
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