Three patients with branch to branch reentrant ventricular tachycardia. Diagnostic and therapeutic considerations.

Three patients with repetitive episodes of relatively slow rate (170 beats per minute) ventricular tachycardia, with right bundle branch block (RBBB) QRS morphology during arrhythmia are presented. The clinical and electrophysiological characteristics and the therapeutic problems raised are analysed. The branch to branch reentry mechanism was considered as the underlying mechanism. The peculiar characteristics found in our cases are: almost normal heart, except right bundle branch block in two and left anterior hemiblock in one patient; relatively slow ventricular rate during tachycardia; delayed retrograde ventriculo-atrial conduction during tachycardia; the onset of tachycardia related to atrial or ventricular premature beats; the possibility to stop the tachycardia through ventricular pacing; therapeutical point of view, DC shock, ventricular pacing and iv mexiletin HCl were highly effective, but not iv lidocaine.