Safety and efficacy of the ThermoCool SmartTouch SurroundFlow catheter for atrial fibrillation ablation: A meta‐analysis

Abstract Background The ThermoCool Smarttouch Surroundflow catheter (STSFc) is an advanced catheter, which integrating contact force sensing and surroundflow technology. However, comparative data between STSFc and contact force sensing catheter (Thermocool SmartTouch catheter [STc]) are limited. Hypothesis We thought that STSFc might bring more clinical benefits. The aim of this meta‐analysis was to compare the safety and efficiency between the STSFc and the STc for treatment of atrial fibrillation (AF). Methods The Medline, PubMed, Embase, and Cochrane Library databases were searched for studies comparing STSFc and STc. Results Four trials involving 727 patients were included in the study. Pool‐analyses demonstrated that, as compared STc ablation, STSFc ablation was more beneficial in terms of procedural times (standard mean difference [SMD]: −0.22; 95% confidence interval [CI], −0.37 to −0.07, P = .005) and irrigation fluid volume (SMD: −1.94; 95% CI, −2.65 to −1.22, P < .0001). There was no significant difference between STSFc and STc (risk ratio [RR]: 1.02; 95% CI: 0.86 to 1.21, P = .79) for free from AF. Evidence of complications were low and similar for both groups (RR: 0.83; 95% CI: 0.19‐3.55, P = .80). Additionally, patients administered STSFc ablation tended to have shorter fluoroscopic times (SMD: −0.20; 95% CI, −0.63‐0.23, P = .21). Conclusions STSFc ablation was associated with reducing procedural times and irrigation fluid volume. Further, STSFc ablation tended to shorten fluoroscopic times. Therefore, STSFc ablation would be a better choice for AF patients especially in patients with heart failure.


| INTRODUCTION
Atrial fibrillation (AF) is the most common sustained arrhythmia. 1 Advances in electro-physiological technology and increased operator experience over the last decade have permitted catheter ablation to emerge as standard therapy for symptomatic, drug-refractory AF. 2,3 However, obtaining long-term PVs electrical isolation remains challenging with just a single procedure. 4 A lot of work has been made to develop ablation catheter with the intent of increasing long-term efficacy and safety of AF ablation. [5][6][7][8] Open irrigation systems and contact force (CF) sensing represent two important landmarks in ablation catheterization technologies. 5 In recent years, CF-sensing catheters have been developed that can directly quantify tissue contact and provide real-time data to guide ablation. However, earlier irrigation systems of CF catheters utilized a flow system that delivered the irrigating fluid only to the distal surface of the electrode tip, which might result in high volume load and risk of steam pops. 9 The surround flow (SF) entire tip irrigation system features a wide-spread distribution of the irrigating solution (56 irrigation holes), which enables homogenous cooling, protection from thrombus formation with lower flow rate requirements, and reduce incidence of steam pops. 6

| Inclusion and exclusion criteria
Two reviewers (C-CF and G-XF) screened and identified studies that met the following inclusion criteria: (a) patients with drug-refractory symptomatic AF that accepted radiofrequency ablation; (b) patients undergoing treatment by catheter ablation for the first time; (c) comparison between STSF catheter ablation and ST catheter ablation; (d) sample size ≥20; and (e) additionally, to be included, studies needed to provide at least one of the reliable information with regard procedure outcomes, complications and follow-up in both groups.
Exclusion criteria were the following: (a) those studies that included the STSFc group with high power RF energy delivery; (b) an equivocal study design or group allocation; and (c) conference abstracts, case reports, case series studies, editorials, review articles, or non-English language articles.

| Quality assessment and data extraction
Study quality was evaluated by two investigators (J-CL and L-MJ) using the Newcastle-Ottawa Quality Assessment Scale (NOS) for observational studies and Delphi consensus criteria for RCTs. The NOS system consists of eight questions with nine possible points. A star system was used to judge the data according to the selected populations, and the comparability of the groups and exposure/outcome of interest. The NOS ≥7 was judged to be a study of good quality. 11 The preferred reporting items for systematic reviews and meta-analyses amendment to the quality of reporting of metaanalyses statement and recommendations from the Cochrane Collaboration in epidemiology were followed during development of the present systematic review. Data extraction was conducted by mutual agreement, and all potential disagreements were solved by consensus. 12,13 Atrial arrhythmias recrudescence: It is any symptomatic or asymptomatic atrial arrhythmia lasting >30 seconds after completing the blanking period after catheter ablation.

| Outcomes definitions
Major complications: It is defined as complications that required any intervention or prolonged hospital stay; other complications were considered as minor complications.

| Assessment of heterogeneity reported bias and statistical analysis
A meta-analysis of the summary statistics from individual trials was performed. Statistical analysis was completed by an independent statistician (C-CF). Differences in dichotomous variables and outcome endpoints were reported as risk ratio (RR) with 95% confidence intervals (CIs). Continuous variables were analyzed using weighted mean differences or standard mean differences (SMD). Fixed-and randomeffects models used weighting that was based on an inverse variance, which was calculated according to DerSimonian and Laird. 14 Between study heterogeneity was reflected by I 2 > 50%, with a P < .05 deemed a statistically significant. When no significant statistical heterogeneity was identified, the fixed effects model was preferentially used as the summary measure. In cases of statistical heterogeneity, sensitivity analyses were performed to assess the contribution of each study to the pooled estimate by sequentially excluding individual trials time and recalculating the pooled RR estimate for the remaining studies. 15 When pooled analysis still yielded significant heterogeneity, the random-effects model was used. Statistical analysis was performed using the Review Manager version 5.3 software (The Nordic Cochrane Center, The Cochrane Collaboration, 2014, Copenhagen, Denmark).

| Eligible studies
The flowchart of the detailed search process is illustrated in Figure 1.
Initially, 344 potentially relevant manuscripts were identified, of which 56 were duplicates and 240 were excluded after reviewing the titles and abstracts. Of the 48 articles that were retrieved for further examination, 13 review articles, 9 editorial/letters, and 4 case reports or case series articles were excluded. Of the remaining 22 studies, 18 were excluded after a detailed evaluation of the full text due to the following: 3, clinical study design; 10, lack of study end points; 4, reporting duplicate date and 1, comparing STSFc and SFc. Finally, 4 clinical trials were included for analysis.

| Study characteristics
The characteristics of the four trials are summarized in Table 1. A total of 727 patients were enrolled in these trials (471 were allocated to the STSFc group and 256 were allocated to the STc group). Three of the four trials had a prospective design, [16][17][18] and most of the trials had patients that were matched on age, gender, body mass index (BMI) and left atrium diameter between the STSFc and STc groups. One study by Chopra et al expounded that patient baseline characteristics and medical history sections were not significantly different between the two groups, but did not show detailed data in the articles. 19 All studies were rated as having good methodological quality. The results of the grouping ensured the feasibility of this meta-analysis.

| Procedure outcomes
The pooled analysis demonstrated that STSFc ablation significantly   Figure 2D).

| DISCUSSION
The present study might represent the first meta-analysis so far com- The irrigated ablation catheters (TCc) allows deliver a large amount of RF energy to the tissues, and can prevent the risk of overheating at the electrode-tissue interface. 20   Moreover, Plenge et al presented the first prospective trial and controlled data comparing STSFc with STc. It was found that when using STSFc, this resulted in shorter ablation times; additionally, the rate of recrudescence and complications were similar for both groups. 16 In an additional prospective trial by Maurer et al, it was shown that 79.7% of patients from the STSFc group were free from AF (74.3% in the STc group) after a mean follow-up of 12 ± 3 months, even though the result did not reach statistical significance (P = .18), there was a trend towards improved efficacy of the STSFc when compared to STc. 18 Additionally, the Ablation Index (AI), which represents a new lesion quality marker, has been shown to allow acute durable PVI followed by increased long-term success. 27 STc with conventional powers. They found that HPSD using STSFc is safe and led to shorter procedure times with a reduced acute PV reconnection as compared to conventional ablation. 35 Thus, the safe and efficacious application of HPSD using STSFc as identified by more clinical trials, informs us that STSFc might be widely applied in the future for AF ablation.

| Study limitations
This meta-analysis has several limitations: First, publication bias could not be completely excluded, as with any literature search of databases, and inclusion of only published data contributed to bias; Second, the numbers of included studies was limited to only five trials; Third, most of the studies were designed as prospective, nonrandomized trials. Thus, more well-designed and large-scale RCTs are required to confirm the findings; Fourth, in the context of important clinical outcomes from complications and long-term follow-up, the included studies, we acknowledge that fewer studies had reported the related end-points, which made our pooled analysis relatively weak.

| CONCLUSIONS
The present systematic review and meta-analysis demonstrated that STSFc appears to be related to a shorter procedure times than STc, and has a tendency to shorten fluoroscopy times. Compared with STc, STSFc significantly reduces irrigation fluid. Thus, for AF patients, and especially those with HF, STSFc would be a better choice. In addition, STSFc is as effective as STc in terms of long-term success rates for treating AF. Moreover, STSFc may be best applied under situations where the safety and efficacy of HPSD is confirmed by in future studies.

CONFLICT OF INTEREST
The authors declare no potential conflict of interests.

AUTHOR CONTRIBUTIONS
Dr Chao-feng Chen and Dr Xiao-Fei Gao: contributed to design of this work, statistical analysis and wrote the article, Mei-jun Liu: contributed to evaluate quality and retrieved the required data, Chao-lun Jin: contributed to reviewed the literature, performed the selection of the studies and helped gather references for the article. Dr Yi-zhou Xu: contributed to design of this work, revised and approved the final version of the article.

ETHICS STATEMENT
Ethical approval was not necessary to conduct this study.