Bidirectional tachycardia a study of five cases

Five patients with bidirectional tachycardia due to digitalis toxicity associated with severe organic heart disease were studied. The origin of the abnormal rhythm was established with the aid of His bundle recordings in three cases and by indirect clues in the others two. In three cases the origin of bidirectional tachycardia was suprahisian while in two patients it was infrahisian. In one patient the transition from junctional to ventricular tachycardia could be observed. Bidirectional tachycardia appears to be a complex arrhythmia in which similar electrocardiographic configuration can be due to different mechanism. Digitalis toxicity was often a causal factor.