Potential arrhythmic substrate of atrial fibrillation at the left atrial diverticulum.

Catheter ablation therapy for persistent atrial fibrillation (PeAF) is both difficult and has limited outcomes. The mechanisms underlying the development and persistence of atrial fibrillation (AF) are not fully understood; therefore, ablation strategies are diverse. A 45-year-old man was referred to our hospital for persistent atrial fibrillation to undergo radiofrequency catheter insertion (RFCA). In the first session we conducted pulmonary vein isolation and additional linear ablation, including that of the roof line and posterior inferior line (posterior box lesion) as the stepwise ablation. However, AF was recurred in six months, therefore he was readmitted for second session ablation preoperative 3D computed tomography (CT) scan for drug-refractory PeAF was performed. The additional isolation of the left superior pulmonary vein and potential drivers of AF by mapping wavefront propagation using multipolar catheters by CARTOFINDER (Biosense Webster, Inc, Diamond Bar, CA, USA) was conducted. However, AF did not terminate. Tomography revealed that the left atrial (LA) diverticulum (LAD) was found uniquely. Electrophysiological findings showed focal firing of the myocardial sleeve and LA diverticulum by an approach for defragmented potentials by re-visiting in interval confidence level (ICL) mode included in the electroanatomical mapping system (CARTO 3, Biosense Webster, Inc, Diamond Bar, CA, USA) and the ablation by encircling this site finally made AF terminate. The AF has not recurred for more than 12 months without the use of antiarrhythmic drugs. This case report suggests that additional ablation around substrates in LAD may be effective for treating refractory AF.