Fig. 1

Radiofrequency ablation in a 6-year-old boy weighing 22 kg who had recurrent ventricular tachycardia nearly every month despite sotalol 6 mg/kg/day. a The surface electrocardiography showed left bundle branch block with inferior axis. b–d. During induced ventricular tachycardia, earliest signal (− 33 ms) was recorded in RVOT septal area. The VT focus was 6–8 mm above His (pink dot) in this child. Yellow dot: Pulmonary valve annulus, Red dot: Ablation sites, Blue dot: Point of VT termination