6 Hybrid Therapy of Bepridil and Catheter Ablation: Practical Strategy to Conquer Chronic Atrial Fibrillation with Supplementary Low-dose Antiarrhytymic Treatment(Latest Challenge of Ablation for Chronic Atrial Fibrillation-Where are We Now and Where are We Going?-,Symposium 6 (SY-06) (H),The 73rd Annual Scientific Meeting of The Japanese Circulation Society)