Verification of electrical isolation of pulmonary veins following left atrial circumferential ablation may require sinus rhythm.

A 67-year-old female with symptomatic paroxysmal atrial fibrillation (AF) underwent left atrial circumferential ablation, and during the procedure, she developed AF. Once the ablation was complete, the left upper pulmonary vein (LUPV) appeared to continue in a rapid disorganized rhythm, despite further attempts at isolating this vein. When the patient was electrically cardioverted to sinus rhythm to assist mapping, the LUPV remained in a disorganized rhythm, pulmonary vein (PV) fibrillation. This case illustrates a possible pitfall in confirming complete isolation of the PVs during AF.