Determinants of successful ablation of idiopathic ventricular tachycardias with left bundle branch block morphology from the right ventricular outflow tract

The aim of the study was to define the factors that may predict the outcomes of radiofrequency oblation from the right ventricular outflow tract (RVOT) in patients with idiopathic VT with a QRS morphology of LBBB. Endocardial mapping and RF ablation from the RVOT were performed in 35 patients (14 men, mean age 41 +/- 14 years), and VT was successfully ablated in 30 patients, There was no significant difference with regard to clinical characteristics and electrophysiological findings between patients with successful and failed ablation. The VTs with successful oblation showed an rS (n = 16) or QS (n = 14) pattern in lead V-1, and all five, VTs with failed ablation showed an rS pattern in lead V-1. Although the absence of (in H wove in lead 17, did not differ between patients with successful and failed oblation (P = 0.13), the absence of (in R wave in lead V-1 predicted VT successfully ablated from the RVOT (positive predictive value 100%; negative predictive value 24%). The VTs with successful ablation had a median precordial transitional zone at lead V-4 (range V-3-V-6), whereas all five VTs with failed oblation had precordial transition zones at lead V-3 (P = 0.004). Furthermore, a presence of an R wave in lead V-1 associated with a precordial transition zone at lead V-3 predicted VT not successfully ablated from the RVOT (positive predictive value 1004); negative predictive value 100%). In conclusion, some VT with LBBB and inferior or normal axis cannot be ablated from the RVOT. The presence of an R wave in lead V-1 associated with a precordial transition zone at lead V-3 suggest that some VTs may not arise from the RVOT.