Case Presentation
A 67-year-old woman with persistent atrial fibrillation (AF) underwent pulmonary vein isolation using a contact force-sensing catheter (SmartTouch SF, Biosense Webster, CA). We performed an ablation index (AI)-guided circumferential energy application (AI of> 400 at the posterior wall roof and> 450 at the anterior wall) with a target lesion distance of 4 mm. However, the right pulmonary vein (PV) potential remained after the circumferential lesion. The time difference between the P-wave onset to the right superior PV (RSPV) remained constant. From the activation sequence of a circular mapping catheter placed in the RSPV, the earliest activation site was the anterior carina. Additional energy applications were delivered just inside the initial anterior ablation line (Figure 1A) . The right superior and inferior PVs were individually isolated, but they did not require linear carina ablation. After 5 months, the patient was readmitted to the hospital for recurrent AF.
Repeat ablation was performed using a three-dimensional mapping system (CARTO3, Biosense Webster) and reconnection of the RPV was detected. An activation sequence of a circular mapping catheter placed in the RSPV demonstrated the earliest activation site to be the anterior carina. The time difference between P wave onset and RSPV potential was 48 ms, and a conduction delay was not apparent despite the previous ablation. Detailed mapping of the left atrium (LA) was performed using a 1-mm multi-electrode mapping catheter (PentaRay®, Biosense Webster) during sinus rhythm. Activation mapping within a circumferential line demonstrated that the earliest activation site was the anterior carina. This suggested a conduction breakthrough over the anterior line where the myocardium was thick (Figure 1B ). However, a voltage map demonstrated a contiguous circumferential lesion without an apparent gap (Figure 1C ). Where is the gap and where should we ablate?