Left Atrial Diverticula: A Rare Non-Pulmonary Vein Trigger for Atrial Fibrillation

Background Pulmonary vein isolation (PVI) is the cornerstone of the catheter ablation strategy for atrial fibrillation (AF). However, recurrence of AF despite durable PVI suggests the presence of non–pulmonary vein (non-PV) triggers. Left atrial diverticula (LADs) are common anatomic variants but are rarely arrhythmogenic substrates. No standardized guidelines currently address the management of diverticulum-mediated AF Case presentation We report a 48-year-old man with long-standing persistent atrial fibrillation who remained symptomatic despite multiple electrical cardioversions and catheter ablations with repeated pulmonary vein re-isolation. During a fourth ablation procedure using pulsed-field ablation, high-density electroanatomic mapping revealed a discrete region of preserved voltage on the superior posterior wall of the left atrium. Intracardiac echocardiography demonstrated a corresponding sac-like outpouching consistent with a left atrial diverticulum. Given the thin wall of the diverticulum and its proximity to the esophagus, ablation within the pouch was avoided. Targeted ablation at the ostium of the diverticulum resulted in immediate termination of atrial fibrillation and restoration of sinus rhythm. At the two-month follow-up, the patient remained asymptomatic and had no documented arrhythmia recurrence. Conclusions Left atrial diverticula represent rare but important non-PV triggers of atrial fibrillation, particularly in patients with recurrent arrhythmia despite successful PVI. Multimodal imaging combined with high-density mapping can facilitate identification of these substrates and guide safe, individualized ablation strategies. Further studies are needed to define the prevalence and optimal management of diverticulum-mediated atrial fibrillation.