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 Table of Contents  
ORIGINAL ARTICLE
Year : 2017  |  Volume : 2  |  Issue : 2  |  Page : 37-43

Comparing cryoballoon and radio frequency ablation for atrial fibrillation treatment: A Hospital-based follow-up study


Department of Cardiology, The First Affiliated Hospital of Xi'an Jiaotong University, Xi'an, Shaanxi, China

Date of Submission23-May-2017
Date of Acceptance26-Jun-2017
Date of Web Publication22-Jun-2017

Correspondence Address:
Chaofeng Sun
Department of Cardiology, The First Affiliated Hospital of Xi'an Jiaotong University, No. 76, Yanta West Road, Xi'an 710061, Shaanxi
China
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/ts.ts_12_17

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  Abstract 

Aim: The aim is to evaluate the effectiveness and safety of cryoballoon ablation (CBA) for atrial fibrillation (AF) treatment, and compare it with radio-frequency ablation (RFA). Methods: A retrospective cohort study was conducted among AF patients who received CBA or RFA from November 2014 to January 2017 at The First Affiliated Hospital of Xi'an Jiaotong University. All patients were followed up from discharge date to either occurrence of death or April 2017. Results: Totally, 154 patients were identified who met the inclusion criteria of having episodes of electrocardiogram-documented AF within 2 months before hospitalization, 13 patients were excluded due to predetermined exclusion criteria, 29 (13 in the CBA group and 16 in the RFA group) were lost to follow-up, and 133 patients (57 in the CBA group and 76 in the RFA group) completed follow-up. The primary efficacy endpoints (AF recurrence or repeat ablation) occurred in 17 patients in the CBA group and 29 patients in RFA group (1-year Kaplan–Meier event-rate estimates, 33.2% and 37.9%, respectively; hazard ratio, 0.79; 95% confidence interval [CI], 0.43–1.5; P = 0.50). Long treatment success rate (no AF recurrence or repeat ablation during the follow-up) was 71.2% in CBA group and 64.6% in RFA, respectively (P = 0.47). The primary safety endpoints occurred in 10 patients in CBA group and 19 patients in the RFA group (1-year Kaplan–Meier event rate estimates, 17.3% and 21.2%, respectively; hazard ratio, 0.73; 95% CI, 0.34–1.57; P = 0.65). Conclusion: This paper presents the results of a first-ever study in a Chinese clinical setting and shows CBA had equivalent efficacy and safety in comparison to RAF as a treatment for AF. CBA is a promising new method for AF treatment.

Keywords: Atrial fibrillation, catheter ablation, cryoballoon ablation, radio frequency ablation


How to cite this article:
Wang C, Chen L, Ma H, Sun C. Comparing cryoballoon and radio frequency ablation for atrial fibrillation treatment: A Hospital-based follow-up study. Transl Surg 2017;2:37-43

How to cite this URL:
Wang C, Chen L, Ma H, Sun C. Comparing cryoballoon and radio frequency ablation for atrial fibrillation treatment: A Hospital-based follow-up study. Transl Surg [serial online] 2017 [cited 2017 Sep 24];2:37-43. Available from: http://www.translsurg.com/text.asp?2017/2/2/37/208866


  Introduction Top


Atrial fibrillation (AF) is a major type of arrhythmia and the most common cause of stroke,[1],[2],[3] adversely affecting patients' quality of life (QOL) and increasing mortality risk. The estimated number of individuals with AF globally in 2010 was 33.5 million and the burden associated with AF increased by around 20% in recent two decades.[4] Catheter ablation has been developed as a treatment modality for AF and is recommended by the 2012 expert consensus statement.[5],[6] Two commonly used methods for ablation are radio-frequency ablation (RFA) and cryoballoon ablation (CBA).[7] RFA has been applied in clinical settings for over 10 years and has successfully improved therapeutic outcomes.[5] However, the technical complexity of RFA requires physicians with extensive training in electro-anatomical mapping and point-by-point ablation, which restricted the application of RFA to a few specialized centers and has limited the availability of ablation therapy for AF patients, especially in third world countries.[7],[8]

The emerging technology of CBA provides an alternative to overcoming this barrier: Ablation can be performed much easier with CBA, a far less technologically complicated procedure than RFA.[9] The utilization of cryothermal energy can also provide additional advantages, including increased catheter stability, minimized tissue contraction during healing [10] and limited endothelial disruption and therefore lower incidence of thrombus formation.[11] With many clinical trials showing that CBA is the equivalent of RFA in terms of its efficacy and safety,[12],[13],[14],[15],[16] CBA appears to be an entirely acceptable substitute for RFA.

As a largely underdeveloped part of the world, Asia could potentially benefit from the availability of the CBA procedure for treatment of AF, yet there is no evidence about its efficacy or safety in Asian clinical settings. Therefore, we conducted this study to examine the use of this treatment in China, the most populous third world country in Asia, where its widespread adoption could have the most impact of any nation on that continent.


  Methods Top


Patients

We identified 154 patients with AF who were treated at the First Affiliated Hospital at Xi'an Jiaotong University from November 2014 to January 2017. Patients met the study inclusion criteria if they had episodes of electrocardiogram (ECG)-documented AF during the 2 months before hospitalization. Exclusion criteria were defined as a left atrium (LA) larger than 5.0 cm, a left ventricular ejection fraction (LVEF) of <40%, a New York Heart Association functional class of III or IV, congestive heart failure, stroke or transient ischemic attack within the previous 6 months, previous LA ablation or surgery for AF, a prosthetic heart valve, or an implantable rhythm device.

Baseline characteristics, previous medical history and an ECG measurement were collected from all the study participants at administration day. Patients received either CBA or RFA treatment.

Cryoballon ablation procedure

The risk of ablation was discussed in detail with the patients, all of who provided written informed consent before the procedure. All anti-arrhythmia drugs (AADs) were discontinued at least 3 days before performing the ablation.

All patients underwent transthoracic echocardiography to assess the LA diameter and LVEF, and transesophageal echocardiography to rule out LA thrombus formation before ablation.

During the procedure, a 5-Fr decapolar catheter was positioned in the coronary sinus as a reference and for atrial pacing. A 5-Fr quadripolar catheter was positioned in the right ventricle for stimulation. The LA was accessed through the transseptal route under fluoroscopic guidance using a 15-Fr steerable sheath (FlexCath, Medtronic Inc, Minneapolis, Minnesota, USA). After each pulmonary vein (PV) was mapped, a double-walled CB (Arctic Front, Cryocath, Medtronic Inc) was advanced over the guide wire up to the LA, inflated, and positioned in the ostium of each PV. The balloon size was selected based on the diameter of the PV as established during preprocedure imaging.

Cryothermal energy was applied after the optimal vessel occlusion has been achieved. During this freezing process, the local temperature was monitored continuously from a sensor at the proximal part of the CB.

The left superior pulmonary vein was usually treated first, followed by the left inferior, right inferior, and right superior pulmonary veins. Combined common PVs were likewise ablated to achieve similar electrical blockage. During ablation of the right-sided PVs, the phrenic nerve was continuously stimulated or monitored for continuous movement to avoid phrenic nerve palsy (PNP).

After two freezing sessions, the circumferential mapping catheter was inserted into the PV to assess the occurrence of electrical isolation of pulmonary veins from atrium. Postablation observation was performed for up to 30 minutes to confirm that the PVs had been disconnected from the LA.

Clinical regulation after ablation

All patients were arranged a transthoracic echocardiography routinely within 24 h postablation to rule out pericardial effusion. The patients were also continuously monitored with ECG telemetry. AADs treatment was stopped after performing ablation. AADs treatment could be restarted if AF relapse occurred, in which case the drug class and dosage were documented in detail.

Follow-up

Patients were followed from discharge date to either occurrence of death or until April 2017. Follow-up included out-patient clinic visits at 1, 3, 6, and 12 months after discharge. Each visit included an interview, physical examination, 12-lead ECG, and 24-h Holter monitoring as necessary. All patients were contacted by telephone at regular intervals during the follow-up period.

Endpoints

The primary efficacy endpoints were the first-documented clinical failure (AF recurrence or repeat ablation). AF recurrence was defined as documented episodes of AF (>30 s) in the ECG or the occurrence of undocumented symptoms of AF (>30 s). The first 90 days after ablation was set as blank period, as many other researches do. Any AF recurrence during blank period was not counted in the determination of clinical failure, because early recurrence after ablation is usually caused by inflammation or incomplete lesion healing, and has little relation to long-term outcome.[5] Secondary efficacy endpoints include ablation time, mean ablation temperature, the first re-hospitalization for cardiovascular causes, and QOL, as measured using the 36-item short-form (SF-36) score.[17],[18] The primary safety endpoints were a composite of serious procedure-related adverse events, death from any cause, stroke or transient ischemic attack, and hemorrhagic events.

Statistics

Categorical variables are presented as frequency values and compared using Chi-square tests. Continuous variables are presented as a mean ± standard error of the mean and compared using Student's t-test. All survival analysis was performed using Kaplan–Meier analysis and Log-rank test. All statistical tests were two-tailed, and P < 0.05 was considered indicative of statistical significance. All analysis was performed using SPSS (version 22, SPSS Inc. Chicago, USA).

Ethics statement

All procedures in this study were in accordance with the ethical standards of the responsible committee on human experimentation (institutional or regional) and with the Helsinki Declaration of 1975, as revised in 2000. This study was approved by the Ethics Committee of the First Affiliated Hospital of Xi'an Jiaotong University (protocol number XJTU1AF-CRF-2015-007). All patients signed an informed consent for participation in the research.


  Results Top


Patients

The flowchart of the study is shown in [Figure 1]. In total, 154 patients were identified as meeting the inclusion criteria. A total of 13 patients were excluded due to predetermined exclusion criteria and 141 were included in the study cohort, 29 of whom (13 patients in the CBA group and 16 in the RFA group) were lost to follow-up. The clinical characteristics at admission and the medication history of all patients are presented in [Table 1]. All the characteristics were about equally balanced between the two groups.
Figure 1: Flow chart for study. AF: Atrial fibrillation; RFA: Radiofrequency ablation; CBA: Cryoballoon ablation; LA: Left atrium

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Table 1: Characteristics of the patients at baseline

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Acute procedure success

During the ablation procedure, complete electrical PV isolation, which indicates the success of ablation, was achieved in 97.8% (218/223) pulmonary veins in the RFA group and 98.0% (292/298) of pulmonary veins in the CBA group (P = 1.00). In the CBA group, 47.8% of the veins were ablated with a 23-mm balloon while the remainder were ablated with a 28-mm balloon.

Efficacy endpoints

As shown in [Table 2], the primary efficacy endpoints occurred in 17 patients in the CBA group and 29 patients in the RFA group (1-year Kaplan–Meier event rate estimates, 17.3% and 21.2%, respectively; hazard ratio, 0.73; 95% confidence interval [CI], 0.34-1.57; P = 0.65). The survival curves for the two groups are shown in [Figure 2]. No significant differences were found between the two groups. Results regarding the secondary efficacy endpoints are also shown in [Table 2]. The mean total procedure time was shorter in CBA group than in RFA group while the mean total fluoroscopy time was longer in CBA group. There were no significant differences between two groups in ablation time.
Table 2: Efficacy end points

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Figure 2: Survival of patients. RFA: Radiofrequency ablation; CBA: Cryoballoon ablation

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SF-36 is a 36-item short-form to survey health status and quality-of-life. It has been widely used in clinical practice and research.[17],[18] In this study, patients in the CBA group had a higher SF-36 score than those in the RFA group, indicating a higher QOL among CBA-treated patients.

Safety endpoints

The primary safety endpoint occurred in 10 patients in the CBA group and 19 patients in the RFA group (1-year Kaplan–Meier event rate estimates, 17.3% and 21.2%, respectively; hazard ratio, 0.73; 95% CI, 0.34–1.57; P = 0.65). All safety endpoint data are presented in [Table 3]. The most common safety endpoint occurring during treatment was hemorrhagic events while the most frequent procedure adverse events was groin-site complications. One patient, who was the second one undergoing CB ablation in our center, suffered pericardial tamponade that required surgery. Her condition was stable after the heart repair surgery, and she had fully recovered at discharge.
Table 3: Safety end points

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  Discussion Top


In this study, we examined the efficacy, safety, and procedural profiles of two ablation technologies used for AF treatment, RFA and CBA. There were no significant differences between the two treatment groups on either the efficacy or safety endpoints that we quantified. In other words, our study demonstrated that CBA has the same efficacy and safety as RFA. Considering the less technology complexity and other advantages mentioned previously, CBA can work as a great substitution of RFA for AF ablation treatment.

Efficacy of cryoballoon ablation in Chinese population

There have been many clinical studies comparing CBA and RFA, including some large, multiple-center studies based on population of Europe and America.[7],[12],[14],[15],[16] The majority of these studies have shown statistical equivalence in efficacy between the two groups, with one exception showing a higher efficacy of CBA.[13] One-year survival rates have varied between studies, with little difference between CBA and RFA treatment groups. Our research is the first one based on Chinese patients and showed similar results with these reported researches. There were no significant differences in the recurrence rate between two groups. Eighty percent of the recurrence happened within the first 6 months after ablation in both groups, which emphasizes the need for better early stage clinical management after ablation.

As many other researches showed, the fluoroscopy time was longer in CBA group than in RFA group. During the CBA procedure, contrast agent was injected to LA and was tested by fluoroscopic examination, to prove the occlusion of pulmonary veins by the balloon, which lengthened the fluoroscopy time. In contrast, RFA does not need occlusion angiography. However, the single-step circumferential ablations mode of CBA is much easier and faster than electroanatomical mapping in RFA procedure, which resulted in shorter total procedure time in CBA group.

Safety of cryoballoon ablation in atrial fibrillation treatment

In addition, almost all studies have shown equivalent safety profiles between CBA and RFA. In this study, the most common procedure-related safety events in both groups were groin-site complications. Groin hematoma can occur during any blood vessel puncture, especially when a large-diameter catheter is needed. In our study, two patients suffered groin hematoma. The hematoma was absorbed after conservative treatment, but it prolonged the hospitalization for these two patients.

The only patient who experienced the serious adverse event of pericardial tamponade was the second one receiving CB ablation in our center, and hence this may be resulted from the “early effect” when operators were faced with new intervention method. No serious adverse events occurred in subsequent cases.

Right PNP is the most common adverse event for CBA reported in the literature, occurring in around 5% of individuals (range: 2.7%–7%),[16],[19],[20] and is related to the application of smaller balloons.[10],[21] In this study, 23-mm balloon was applied in 47.8% of the patients. Special care was taken during the surgical procedure to protect the right phrenic nerve. During the procedure, continuous phrenic nerve stimulation was applied through a right atrial stimulation catheter, or phrenic nerve movement during spontaneous breathing was observed to ensure that this movement was not affected. Finally, no instance of PNP was observed in our study.

Cryoballoon ablation improving quality of life of patients

Compared with the acute and long-term success of procedure, improvement in the QOL of patients may have more significance when evaluating a therapy. Our research first survey the QOL between two groups and showed patients after CBA treatment have higher life quality when compared with that received RFA treatment. The evaluation of QOL after ablation could be contributed to the elimination of the AF symptoms. After ablation procedure, some patients still need AADs to prevent the recurrence of AF, although the class and dosage of drug were significant reduced. Our research recorded the category and dosage of the AADs in detail and find a less need of AADs in CBA patients. The higher QOL of patients in CBA group may be related with the less AADs use.

Meaning of the study

This study demonstrated that CBA is equivalent to RFA in the treatment of AF patients, and is the first study to compare the efficacy and safety of these two treatments in a clinical setting in China. We believe that this is an important finding for medical professionals and AF patients in developing countries throughout the world, where experienced physicians with the sufficient electrical physiology knowledge to perform RFA are limited in number and thus, effective ablation treatment may not be available. The lower technical knowledge threshold necessary to perform CBA makes it particularly well-suited for utilization in less developed areas. This study is the first one to take QOL of patients into account and provides long-term prognosis data concerning AF treatment, and showed higher QOL in CBA patients. These all will help physicians and patients to choose the most appropriate procedure and provide them with accurate expectations.

Limitations and future study

Still an emerging technology, CBA has been hindered from broad application due to efficacy and safety concerns and local regulatory restrictions. This article presents the results of a study of this procedure, in comparison with RFA, as treatment for AF at a hospital in Northwest China, but relatively a few cases could be obtained and randomized group design was impossible. Future investigation will involve other institutions to set up a large multi-center randomized control trial for statistically more convincing results.

In conclusion, this study shows the equivalent efficacy and safety of CBA for AF treatment in Chinese population when compared with RFA, indicating a potential wide application of CBA in developing areas.

Financial support and sponsorship

This work was supported by the Clinical Research Award of the First Affiliated Hospital of Xi'an Jiaotong University, China (No.XJTU1AF-CRF-2015-007).

Conflicts of interest

There are no conflicts of interest.

 
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