Introduction
Pulmonary vein (PV) isolation (PVI) with radiofrequency (RF) catheter ablation is an established strategy for treating atrial fibrillation (AF).1 When RF energy is applied to the left atrial (LA) posterior wall adjacent to or near the esophagus, a special care needs to be taken because of the thermal injury of the esophagus2,3, and reducing RF energy and contact force and shortening application time generally recommended.4 For localization of the esophagus during the PVI procedure, an esophageal temperature probe to monitor esophageal temperature is widely used.5,6 Esophagography by asking the patient to swallow the contrast medium just before the procedure is also useful.7,8
Intracardiac echography (ICE) with the use of a Carto SoundStar® ultrasound catheter (Biosense Webster, Diamond Bar, CA) is useful for not only transseptal puncture but creating the LA 3-dimensional (3D) image from the right atrium. This LA 3D echo image can be used for integration with the LA 3D computed tomography (CT) image with the assist of the CartoMergeTM module (Biosense Webster) with a high accuracy.9 In our laboratory, by inserting the Carto SoundStar® catheter into the LA cavity through the long sheath advanced to the LA, we have attempted to visualize the LA posterior wall (LAPW) and the esophagus from the LA. This method seemed to allow us to create the 3D esophagus image adjacent to the LAPW in a real-time fashion during the AF ablation procedure and assess the direct relationship between the esophagus and LAPW. The purpose of the study was to validate the present method of esophagus visualization and analyze the LAPW thickness adjacent to the esophagus. We further assessed the outcome after ablation-index (AI)-guide circumferential PVI with a relatively low target AI value on the esophagus region confirmed by the ICE.