The Japanese Catheter Ablation Registry (J‐AB): A prospective nationwide multicenter registry in Japan. Annual report in 2018

Abstract Background To analyze the type of ablation procedure, acute outcomes, and complications related to catheter ablation in Japan during the year of 2018. Method The Japanese Catheter Ablation (J‐AB) registry is a voluntary, nationwide, multicenter, prospective, observational registry, performed by the Japanese Heart Rhythm Society (JHRS) in collaboration with the National Cerebral and Cardiovascular Center using a Research Electronic Data Capture system. The procedural outcome and complications during hospitalizations were collected. Result A total of 55 525 procedures (mean age of 64.5 years and 66.5% male) from 369 hospitals were collected. The total number of target arrhythmias was 61 610 including atrial fibrillation (AF, 65.6%), atrial flutter (AFL) or atrial tachycardia (16.7%), atrioventricular nodal reentrant tachycardia (7.4%), atrioventricular reentrant tachycardia (3.5%), premature ventricular contractions (4.1%), and ventricular tachycardia (VT, 2.0%). Over a 90% acute success rate was observed among all arrhythmias except for VT due to structural heart disease, and notably, an over 99% success rate was achieved for pulmonary vein isolation of AF and inferior vena cava‐tricuspid valve isthmus block for isthmus‐dependent AFL. Acute complications during hospitalization were observed in 1558 patients (2.8%), including major bleeding (Bleeding Academic Research Consortium: BARC criteria ≥2) in 1.1%, cerebral or systemic embolisms in 0.2%, and death in 0.1%. Acute complications were more often observed with AF ablation (P < .001), especially the first AF ablation session and with structural heart disease (P < .001). Conclusion The J‐AB registry provided real‐world data regarding the acute outcomes and complications of ablation for the various types of arrhythmias in Japan.


| INTRODUC TI ON
Catheter ablation has become an established therapy for the management of various cardiac arrhythmias. It has been reported that catheter ablation is performed in up to 300-600 patients per one million of the population annually in European countries 1,2 and the total number in Japan has exceeded 70 000 per year and is still increasing. 3 However, little is known about the details of the ablation procedures including the type of target arrhythmias, outcomes, and acute complications related to the ablation procedure.

| ME THODS
The data from the J-AB registry during the year of 2018 was used in this study. This nationwide registry was a voluntary one and started in August 2017. The method of this registry has been previously reported elsewhere. 4 In brief, the study consisted of patients who were treated with any type of catheter ablation for any type of arrhythmia. Patients who received surgical management for arrhythmias were excluded from this registry. The data on the patient background (age, sex, and underlying heart diseases), target arrhythmias, outcome of the procedure (

| Statistical analysis
The continuous variables were expressed as the means ± standard deviation (SD). Categorical data are reported with frequencies.
Statistical tests of the differences were performed applying the Chi-square test or Fisher's exact test as appropriate between patients with AF and non-AF ablation, between the first and second or greater sessions for a different AF type, or between patients with and without structural heart disease. A P value < .05 was considered statistically significant, and all tests were carried out as two-sided.

| Patient background and target arrhythmias
The mean age was 64.5 ± 13.4 years, and 66.5% were male.
Underlying heart diseases were observed in 10 577 patients (19.1%), including ischemic heart disease (IHD) in 6.1%, nonischemic cardiomyopathy in 5.4%, valvular disease in 3.2%, and congenital heart disease (CHD) in 1.3% (  Figure 2). Over a 95% success rate was observed for slow pathway ablation of AVNRT (complete and partial success was achieved in 96.9% and 2.0%, respectively) and accessory pathway ablation of AVRT (complete success in 96.0%). A high success rate was observed for uncommon AFL/macro reentrant AT (complete and partial success was achieved in 82.5% and 11.3%, respectively), focal AT (complete and partial success was achieved in 82.2% and 12.6%, respectively), PVCs (complete and partial success was achieved in 73.9% and 18.2%, respectively), and idiopathic VT (complete and partial success was achieved in 77.6% and 15.2%, respectively).

| Acute outcome of the ablation procedure
Compared to the other arrhythmias, the successful ablation rate of VT due to structural heart disease had a low but acceptable result: VT due to ischemic cardiomyopathy (complete and partial success was achieved in 50.3% and 36.2%, respectively), VT due to nonischemic cardiomyopathy (complete and partial success was achieved in 96.9% and 2.0%, respectively), and VT due to congenital heart disease (complete and partial success was achieved in 46.7% and 46.7%, respectively). We also analyzed the influence of structural heart disease on the success rate of other arrhythmias.   (Table 4). For AF ablation, we performed another analysis of the cases stratified by the AF type and number of ablation sessions. Acute complications were more frequently observed during the first session for paroxysmal AF due to the occurrence of phrenic nerve paralysis and during the first session for non-paroxysmal AF ablation due to gastric hypomotility (Table 5). In addition, we analyzed the acute complications in patients with structural heart disease. Table 6 shows that acute complications were more frequently observed in those with structural heart disease. One patient overlapped. During the past two decades, the number of ablation cases has dramatically increased. Data from a Japanese nationwide database using the administrative case-mix Diagnostic Procedure Combination (DPC) system (ie, the Japanese Registry Of All cardiac and vascular Diseases

| D ISCUSS I ON
[JROAD]-DPC) has reported that the total number of ablation cases has exceeded 70 000 and is still increasing. 3 However, the details of the procedures (type of targeted arrhythmias, success rate or complications during the ablation procedure, and current strategy, etc) have been lacking. Accordingly, the J-AB registry was conducted to clarify the efficacy and safety in the real-world setting. 4 This study was started in August 2017 and was expected to initially collect data from around 250 hospitals, but the number of participating medical institutions increased to over 350 hospitals by the end of 2018. year. 5 That registry consisted of 16 566 procedures per year in 2018, but they used questionnaires to collect the data from 100 selected centers. In Germany, the German Ablation Quality Registry was conducted to clarify the specific ablation procedures for selected arrhythmias (AF, 6 PVC, 7 and PSVT 1 ) but that registry also used the data from 52 selected hospitals. In the United States, large-scale ablation data were reported (50 969 ablation recipients during the years of 2011 to 2014), but that report used the retrospective data from the Nationwide Inpatient Sample (NIP) database, and specifically collected in-hospital complications associated with AF ablation. 8 In Japan, we previously reported similar registry results focused on AF ablation, named the Japanese Catheter Ablation Registry of Atrial Fibrillation (J-CARAF 9 :

| Comparison with other studies
total 10 795 AF ablation session data from a mean of 165 hospitals), but the data were still obtained from selected hospitals and focused on the complications during AF ablation. Accordingly, the current J-AB registry was quite unique in that it collected data on all ablation cases from 369 participating hospitals to examine the efficacy and safety.

| Acute successful rate of ablation procedures
In this J-AB registry, two-thirds of the ablation targets were AF and that number was quite a high prevalence as compared to the other , 64 in non-PAF) could not categorized as first or ≥second session due to missing data. About 24 patients (18 in pAF patients; 6 in non-pAF) had missing data to complications during hospitalization. b 3 patients with pAF and 4 patients with non-pAF had missing data to death during hospitalization. countries. 1,2,6 The success rate of the target arrhythmias was more than 90% for atrial arrhythmias (AF, AFL, AT, and PSVT) but was below 90% for ventricular arrhythmias, especially in patients with ischemic or nonischemic heart diseases. This trend was similar to the other countries. 5,6 However, the success rate for atrial arrhythmias (AF, AFL, AT, and PSVT) did not differ between the patients with and without structural heart disease. Balloon ablation for pulmonary vein isolation became available since 2014, and 34.7% of the first AF ablation procedures used balloons in 2018. Balloon ablation will become more popular in Japan.

| Acute complication rate of the ablation procedures
The most important results were the rate of acute complications during the procedures. In this registry, acute complications were observed in 2.8% of all procedures. Major bleeding was 1.1%, cardiac tamponade 0.6%, embolic complications 0.2%, esophageal injury 0.2%, pericarditis 0.2%, sick sinus syndrome 0.2%, and AV block 0.1%. In particular, complications other than AV block were more commonly observed in AF ablation, and acute complications occurred in 3.2%, including major bleeding in 1.2%, cardiac tamponade in 0.7%, embolisms in 0.2%, phrenic nerve injury in 0.6%, and esophageal injury in 0.2%. Compared to the previous reports in other countries, acute complications during hospitalization were similar or low. In the Spanish Catheter Ablation Registry, the rate of all complications was 2.0%-2.6% for all ablation procedures, and 3.4%-5.1% for AF ablation. 5 In the German Ablation Registry, minor and nonfatal complications occurred in 3.5% (≥75 years of age) and 4.2% (<75 years of age) of AF ablation cases, respectively. 6 In the US report, the overall complication rate was 5.46% and the in-hospital mortality rate was 0.15% for AF ablation. 8 In the J-CARAF during the years from 2011 to 2016, total major complications occurred in 3.0% of the AF ablation procedures. 9 We need to pay more careful attention to avoid periprocedural complications during AF ablation. Among the acute complications during AF ablation, in this report, we performed another analysis of cases stratified by the AF type and number of ablation sessions. More acute complications occurred during the first session as compared to the second or greater sessions. Among those, phrenic nerve paralysis occurred more frequently during paroxysmal AF ablation, and gastric hypomotility occurred more frequently during non-paroxysmal AF ablation (Table 5). We speculated that phrenic nerve paralysis (n = 211) was due to balloon ablation (158 of 211 case, P < .001; data not shown), but could not find any factors associated with the gastric hypomotility in this study. Further detailed data would be needed to explain that. In particular, the death rate during VT ablation associated with structural heart disease (non-idiopathic VT ablation) was more frequently observed in 12 of 34 cases, as compared to idiopathic VT ablation (1 of 29 cases, P = .002; data not shown). Structural heart TA B L E 6 Acute complications stratified by patients with or without structural heart disease disease is one of the most important factors that raises the complication/death rate after catheter ablation.

| Limitations
There were several important limitations to this registry. First, this registry was voluntary, and more than 70 000 ablation cases were reported from the JROAD-DPC data, thus, this registry did not cover all ablation procedures in Japan. Second, esophageal injury and pulmonary vein stenosis usually occurred late after the ablation procedure, thus, the number stated in this study would have been underestimated in this registry. Third, data monitoring was not performed in this report, thus, the true numbers might differ from this study. Careful attention would be needed to interpret the present results that might have been biased by the limitations inherent to observational studies.

| CON CLUS ION
The J-AB registry 2018 for the first time provided the real-world data regarding the outcome and acute complications of catheter ablation of the various types of arrhythmias in Japan. Ablation therapy is a safe and effective treatment for cardiac arrhythmias, but you still need to pay attention to the development of serious complications during AF procedures.