Efficacy of Early Rhythm Control Therapy in Patients With Subclinical Atrial Fibrillation

Inclusion Criteria: * Among patients with Cardiac implantable electronic device (CIED), subjects with atrial high rate episodes found Cardiac implantable electronic devices: implantable loop recorder, pacemaker, implantable cardioverter defibrillator(ICD), cardiac resynchronized therapy(CRT) * Patients aged 19 or older who have agreed to the study (if voluntary consent is deemed difficult, consent from legal representatives is obtained together) * If the accumulated period of the atrial high rate episode during the three-month observation period is more than 21 hours * Patients whose atrial fibrillation has not been confirmed by electrocardiogram or holter monitoring within the past year from the time atrial high rate episode was detected However, enrollment is possible even if it includes one of the following two cases ⓐ Patients diagnosed and recorded as atrial fibrillation on medical records but not confirmed by electrocardiogram or holter monitoring ⓑ If there is a record of atrial fibrillation, but Paroxysmal AF less than 30 seconds Exclusion Criteria: * Patients deemed inappropriate to participate in the study by the investigator * Patients diagnosed with atrial fibrillation with 12-lead electrocardiogram or holter within the past year prior to participation in the study * Patients taking Class Ic, III of antiarrhythmic drugs prior to study participation * Patients who have had rhythm control treatments such as Radiofequency catheter ablation (RFCA), Total thoracoscopic ablation (TTA), Maze procedure (MAZEop), and antiarrhythmic treatment due to atrial fibrillation (except for CTI ablation with AFL) * Patients whose life expectancy is less than one year (e.g., patients who can't even have a heart transplant, patients who receive DNR, Patients in hospice wards who refuse life-sustaining treatment, terminal cancer patients who cannot receive radiation or chemotherapy, etc.)