Follow-up was performed every 1–2 months at the outpatient clinic. Patient history and 12-lead electrocardiograms were recorded at every visit. If patients experienced symptoms suggestive of arrhythmia between scheduled visits, they were instructed to visit the emergency department. Electrocardiography was performed to identify the cause of their symptoms. Recurrence of AF was defined as documentation of AF lasting more than 30 s and confirmed by ECGs. The first 3 months after CA were defined as the blanking periods for recurrent AF.15 If AF was identified during the blanking period, cardioversion was performed and sinus rhythm restoration was confirmed.