<qa>  What is the likely predominant mechanism of ablation for non-paroxysmal AF?Catheter ablation for non-paroxysmal AF is more complex as triggers, if present at all, are not immediately apparent, but the abnormal atrial substrates are the likely predominant mechanisms. Additional catheter ablation strategies targeting for atrial substrate modification have been introduced. The common strategies involve either application of empirical linear lesion sets in the atrial areas or ablation of atrial areas with complex fractionated atrial electrograms in addition to pulmonary vein isolation. Nevertheless, the corresponding success rates in long-term sinus rhythm maintenance are modest. 