Usefulness of non‐contact mapping for catheter ablation of ventricular tachycardias originating at the right ventricular outflow tract

Background Different QRS morphologies are often observed in idiopathic ventricular tachycardias or premature ventricular contractions originating from the right ventricular outflow tract (RVOT). However, the precise mechanism underlying multiple QRS morphologies has not been clarified adequately. The purpose of this study was to examine the mechanism underlying different QRS morphologies in RVOT arrhythmia. We also investigated the usefulness of non‐contact mapping guided radiofrequency catheter ablation for RVOT arrhythmia. Methods Endocardial mapping of RVOT was performed using a non‐contact mapping system in 20 patients with RVOT arrhythmia. We analyzed the underlying mechanism that produces different QRS morphologies during catheter ablation of RVOT arrhythmia. Results Forty‐six QRS morphologies of RVOT arrhythmia were observed in 20 patients. Five patients showed monofocal QRS morphology, whereas the remaining 15 patients showed multiple QRS morphologies (from 2 to 4 morphologies each). Among these, all patients presented a shift in the origin of tachycardia. Additionally, different QRS morphologies were observed in 5 of these patients that were caused by a change in the local activation after radiofrequency energy delivery. Radiofrequency energy application to the site of origin of the RVOT arrhythmia using non‐contact mapping navigation eliminated the RVOT arrhythmias in all patients. However, 1 patient presented a recurrence of RVOT arrhythmia (success rate, 95.0%). Conclusions The multiple QRS morphologies of RVOT arrhythmia were caused by a shift in the origin of tachycardia or by a change in the local activation following the radiofrequency energy application. Non‐contact mapping was useful to identify the appropriate target site of RVOT arrhythmia irrespective of the changes in QRS morphologies.