''Idiopathic'' Ventricular Tachycardia. Idiopathic ventricular tachycardias occur in ''normal'' hearts and are generally benign arrhythmias, They can arise from either the left or right ventricle, and the origin is usually predictable from the surface EGG. These arrhythmias are produced by diverse mechanisms, When treatment is indicated, empiric pharmacotherapy can be successful. However, if drugs are not tolerated or fail, radiofrequency (RF) ablation may be indicated. During electrophysiologic study, arrhythmia mechanism can be determined, and pace and activation mapping can be used to localize the site of ventricular tachycardia origin to direct application of RF lesions. RF ablative therapy has been associated with high success rates.