Efficacy and Safety Outcomes of Catheter Ablation of Non-valvular Atrial Fibrillation in Korean Practice: Analysis of Nationwide Claims Data

Background and Objectives: The aim of this study was to investigate the effectiveness and selected adverse events of radiofrequency catheter ablation in patients treated for drug-refractory atrial ﬁbril-lation (AF) using claims data provided by the Health Insurance Review and Assessment Service, which covers all ablation procedures conducted in South Korea. Subjects and Methods: The study population included patients who underwent catheter ablation for AF between January 2011 and December 2013. A total of 3,850 patients without a previous history of catheter ablation procedure were enrolled. We analyzed 2-year effectiveness of the index ablation. Any redo ablation, electrical car-dioversion, or use of antiarrhythmic drug beyond the blanking period of 3 months was considered a failure of index ablation. Results: Overall recurrence rate following AF ablation was 61.1%. The recurrence rate was lower in patients under 65 years old than in those over 65 years old (hazard ratio [HR] 0.89; 95% conﬁdence interval [CI], 0.81 to 0.97, P=0.009). Repeat ablation was more frequent in men (HR 1.56; 95% CI, 1.20 to 2.04; P=0.001) and patients under 65 years old (HR 1.79; 95% CI, 1.34 to 2.38; P<0.001). Electric cardioversion was more frequent in men (HR 1.35; 95% CI, 1.06 to 1.72; P=0.014) than in women. The overall rate of stroke, blood transfusion, signiﬁcant pericardial complication, and cardiopulmonary resuscitation was 0.5%, 4.8%, 2.7%, and 0.2%, respectively. Conclusions: In the present study, old age was associated with treatment failure of catheter ablation for drug-refractory AF in the Korean population. Overall recurrence did not vary with respect to sex.


Introduction
Percutaneous catheter ablation has emerged as a potentially curative interventional tool for rhythm control in patients with atrial fibrillation (AF). 1 In selected patients, radiofrequency catheter ablation has been demonstrated as superior to current antiarrhythmic drug therapy in maintaining sinus rhythm, symptom relief, and preventing hospitalization. 2

Data source
Data were retrieved from the HIRA database, which contains population and reimbursement data from the national health insurance service. The HIRA database includes diagnosis (International Classification of Disease, 10 th revision [ICD-10]), procedure records, prescription records (drug name, formula, dose, and duration of prescription), and demographic information. 3

Study Population
The study population included patients who underwent catheter ablation (M6542) for AF between January 1, 2011 and December 31, 2013. Only patients with no previous history of catheter ablation procedure were included, so that the ablation of interest was the first procedure in a given patient and was considered the index ablation. Patients who underwent catheter ablation for any atrial arrhythmia before the index procedure were also excluded. Thus, a total of 3,850 patients were enrolled ( Figure 1). Admission codes were not analyzed because we considered that admission would be mandatory for AF ablation in South Korea.
The HIRA database does not contain clinical data. Types of AF, such as paroxysmal, persistent, or permanent, and duration of AF cannot be discriminated. For catheter ablation to be reimbursed by healthcare insurance in South Korea, patients should have received antiarrhythmic drug treatment for at least 6 weeks. In addition, pulmonary vein isolation using cryoballoon is not reimbursed. Therefore, AF ablation as a first-line treatment (without previous medical treatment) and cryoballoon ablation procedures are not included in the present study. Surgical ablation cases were also excluded.

Outcomes
The 2-year effectiveness of index ablation was estimated. Any

Statistical Analysis
Continuous variables were expressed as mean ± standard deviation (SD) and and compared using an unpaired Student's

Results
Baseline characteristics are summarized in Table 1. Mean age was 57.0 (±10.8) years and 73.3% of patients were male.
Effectiveness outcomes are summarized in Table 2. Overall recurrence rate following AF ablation was 61.1%. Repeat ablation was more frequent in men and patients under 65 years old than in women and patients over 65 years old, respectively. Electric cardioversion was more frequent in men than women, but age was not a discriminating factor for electric cardioversion. However, the rate of antiarrhythmic drug use after the blanking period was significantly lower in patients under 65 years old than in those over 65 years old. Overall analysis showed that recurrence rate was lower in patients under 65 years old than in those over 65 years old, but it did not vary between men and women. Event-free survival is shown in Figure 2. While repeat ablation and electric cardioversion occurred steadily after the blanking period, use of antiarrhythmic drugs was concentrated between 3 and 6 months.     Table 4 summarizes safety outcomes. Among those who underwent pericardiocentesis (n=105), 55 patients were also given a blood transfusion (42 males, 15 females). Only 1 patient underwent surgery for a pericardial window instead of pericardiocentesis.
Cardiopulmonary resuscitation was performed in 6 patients.

Discussion
Catheter ablation for AF is more effective than antiarrhythmic drug therapy in restoring and maintaining sinus rhythm. 4 In general, it is used as a second-line treatment after failure of or intolerance to antiarrhythmic drug therapy. As first-line treatment, randomized clinical trials have demonstrated that catheter ablation reduce the episodes of atrial arrhythmia 5 and the burden of symptomatic AF. 6 A meta-analysis also showed similar effectiveness benefit 7 and current guidelines recommend the use of catheter ablation as first-line treatment in selected patients. 1,2

Effectiveness analysis
The success rate of catheter ablation in patients with AF is quite variable. Reasons for variable success rates include differences in patient characteristics, AF status, ablation technique or method, definition of procedural success, and follow-up period.   Although catheter ablation was significantly superior to drug therapy, sinus rhythm was maintained in fewer than one-third. or Holter monitoring. 15

Limitations
There are potential limitations to our study. Since we retrieved administrative claims data for patients from a nationwide health insurance database, we could not determine the type or duration of AF, other patient characteristics, and ablation strategy. Second, the definition of AF recurrence in our study is not based on ECG recordings. The decision not to retain sinus rhythm after recurrence of an index procedure was counted as freedom from atrial arrhythmia. Instead, antiarrhythmic drug use for atrial premature complexes or short runs of atrial tachyarrhythmia less than 30 seconds were counted as recurrence. Third, there may have been non-claimed ablation procedures, but their number is presumed to be negligible in South Korea. Regarding safety, important complications such as atrio-esophageal fistula and hospital readmission due to procedure-related complications were not analyzed. Although analysis cane be performed using ICD codes, the code tends to be over-listed for the convenience of reimbursement.
Therefore, we considered ICD codes unreliable for analysis of significant complications related to AF ablation in South Korea.

Conclusion
In the present study, the recurrence rate of catheter ablation for drug-refractory AF in the Korean population using the HIRA database was 61.1%. Patients over 65 years old had a higher recurrence rate than those under 65 years. Overall recurrence did not vary with respect to sex. Repeat ablation was more frequent in men and younger patients.