Gass M, Kühlkamp V, Mewis C, Baden W, Apitz J. Monatsschrift Kinderheilkunde 145(10):1051-1053, 1997. We report about the possibility of electrophysiological diagnosis and therapy in the treatment of a symptomatic left ventricular tachycardia which could not be treated effectively by oral medical therapy in a 10 year old boy with no obvious structural heart disease. By right bundle-bloc-like QRS-complexes in the surface-ECG, the diagnosis of the ventricular origin of the tachycardia was confirmed by transesophageal-ECG. This was followed by the first electrophysiological examination that showed increased left ventricular vulnerability. During this electrophysiological examination the tachycardia was terminated by stimulated singular premature beats. An oral medical therapy with sotalol was started. After the phase of saturation the next ventricular stimulation was done, that showed no sufficient protection of sotalol against VT. So the decision was made for ventricular ablation. After 5 high frequency-applications no furhter ventricular tachycardia could be induced. Since this intervention the patient lives without symptoms