The critical atrial substrates in maintaining persistent atrial fibrillation might be identified by Cycle-Length Mapping (CLM) module. Based on the results of multicenter study in Cycle-Length Mapping between Taipei Veterans General Hospital (Professor Shih-Ann Chen) and IRCCS San Donato Policlinic (Professor Carlo Pappone), targeted CLM driver-ablation provided significant benefits in terms of arrhythmia freedom in the treatment of persistent AF. These findings support a patient-tailored, mapping-based strategy for individuals affected by non-paroxysmal AF. The new ultra-high density mapping catheter, OPTRELL, will be available soon in Taiwan. Therefore, we proposed that the degree of atrial interstitial fibrosis detected by using both unipolar and bipolar voltage map in sinus rhythm and CLM in AF with OPTRELL™ Mapping Catheter would be further better characterization of the atrial substrate and could be potentially critical targeted in eliminating the sources of AF. As additional substrate mapping provided benefits compared to PVI alone in patients with persistent AF, we hypothesize that combination of electrophysiological and substrate-guided ablation strategy using CLM module with OPTRELL™ Mapping Catheter could be used to guide radiofrequency ablation in the patient with non-paroxysmal atrial fibrillation.