Backgrounds: Catheter ablation of recurrent atrial tachyarrhythmia after Maze operation is challenging due to complex arrhythmia circuits. The aim of this study was to clarify the characteristics and ablation outcomes of atrial tachyarrhythmias after Maze operation. Methods and Results: Twenty-eight cases who underwent catheter ablation of post-Maze procedure atrial tachyarrhythmia (42 sessions; 1.5 per patient) in our 5 teaching affiliate hospitals were retrospectively analyzed. Cox-Ⅳ Maze procedure and left atrial Maze were performed in 19 cases and 5 cases, respectively. Mean interval between the surgery and index ablation was 62.4 months. In total, 46 atrial tachyarrhythmias were studied. Reentrant atrial tachycardia (AT) was the most common form (n=36), whereas 4 atrial fibrillation (AF) and 2 focal AT were also observed. Identified tachyarrhythmia circuits were as follows; 16 peri-mitral, 9 left atrial localized reentry (4 septal, 3 posterior, 1 left atrial appendage, 1 anterior), 6 right atrial lateral incision-related, 5 cavo-tricuspid isthmus dependent, 3 roof dependent, 2 right atrial localized reentry (1 coronary sinus, 1 cavo-tricuspid isthmus), 1 bi-atrial reentry, 1 pulmonary vein-left atrial reentrant tachycardia, 2 focal AT (1 para-hisian, 1 coronary sinus), and 1 atrio-ventricular nodal reentry. Termination of targeted tachyarrhythmia was achieved in 34 sessions (81%). AT/AF recurrence free rate at 12, 24, 36 months of follow-up were 91.8%, 81.6%, and 65.3%, respectively. Seven cases underwent multiple sessions (two 2 nd sessions, three 3 rd sessions, and two 4 th sessions). In these cases, de-novo atrial tachyarrhythmias were detected in the repeat procedures. Conclusions: Most of the atrial tachyarrhythmias after Maze operation were incision/gap-related reentrant ATs, among which peri-mitral AT and LA localized reentry were the most prevalent. Although these challenging tachyarrhythmias can be treated with the contemporary mapping techniques, de-novo tachyarrhythmias can emerge in a remote period.

Although late complete atrioventricular block (CAVB) is especially rare as periprocedural complication of atrioventricular nodal re-entrant tachycardia treatment, this complication can necessitate permanent pacemaker implantation. The present case is that this late CAVB can be caused only during periprocedural period by the indirect or functional effects on the fast pathway of AV node because this case has paroxysmal supra-ventricular tachycardia with pre-existing PR prolongation, and the PR prolongation improved within normal PR interval after curing of the late CAVB. Further, when the late CAVB occurs within a few weeks after ablation, such bradyarrhythmia as periprocedural complication may be reversible and indication of a permanent pacemaker implantation should be carefully considered.