Introduction
Catheter ablation has become the indispensable treatment strategy for cardiac arrhythmias1. Detailed 3D mapping can identify the reentrant circuit or origin of tachyarrhythmias and has been very important tool for catheter ablation. Rhythmia mapping system (Boston Scientific, Washington, DC), which uses a small basket array with 64-polar mini-electrodes (IntellaMap Orion, Boston Scientific), enables rapid ultra-high-density mapping in a short time2-4. The most advantage of this system was little need for additional manual annotation and easily identifies the reentrant circuit3-4. Previous reports had demonstrated the usefulness of this system for several complex arrhythmias such as an atrial tachycardia after congenital heart disease surgery, and ventricular tachycardia5-8. However, there were only a few reports of investigation about the efficacy of this system in patients with accessory pathway (AP). We previously reported that Rhythmia system can create the atrio-ventricular dual chamber mapping, which would be useful to understand the details of the connection of the AP between atrium and ventricle9. We hypothesized that the atrio-ventricular dual chamber map would be useful for the effective radiofrequency (RF) application to the AP patients. The aim of this study was to investigate the utility of Rhythmia system for catheter ablation of AP.