705-4 Idiopathic Right Ventricular Outflow Tract Tachycardia: Narrowing the Anatomic Location for Successful Ablation

Abstract

Pace-mapping is the primary technique used to localize the origin of ventricular tachycardia (VT) from the right ventricular outflow tract (RVOT). We previously divided the RVOT septum into 9 equal sites (see figure) and developed a surface ECG algorithm for identifying the 9 paced sites based on the orientation of the QRS complex in leads I and aVL and the precordial R wave progression. Based on this algorithm and initial experience with catheter ablation of RVOT-VT, we hypothesized that most RVOT-VTs originate from a limited area in the RVOT, corresponding to the mid to anterior and superior RVOT septum just below the pulmonic valve (sites 2 & 3). To test this hypothesis, we documented fluoroscopically the site of identical pace-maps and successful radiofrequency (RF) catheter ablation of RVOT-VT in 14 consecutive patients (12 female; ages 23–66 years). All patients presented with palpitations and/or presyncope and left bundle branch block/inferior VT with a right (n = 5) or left (n = 91 axis. Each patient had a structurally normal heart. A lesion was considered successful if no tachycardia could be induced with atrial or ventricular pacing (± isopreterenol) after having been reproducibly initiated prior to lesion application. In each patient, the site of best pace-map and successful ablation was site 2 or 3 (The figure represents a right anterior oblique view of the right ventricle. In most patients with RVOT-VT, the site of successful RF catheter ablation was in the mid to anterior and most superior aspect of the RVOT septum. These findings may simplify the approach to RF catheter ablation of RVOT-VT and thus decrease fluoroscopic exposure in these patients.