RESUMO
Unusual tachyarrhythmia is characterized by a beat-to-beat alternation of the axis of the QRS complexes, the bidirectional tachycardia have multiple mechanisms and aetiologies. We report the observation of a 75-year-old man having a hypertensive dilated cardiomyopathy with chronic atrial fibrillation and treated by diuretics, digitalis and platelets antiaggregants. He presented with a global congestive cardiac failure. The electrocardiogram revealed a bidirectional tachycardia with a regular alternation of the QRS axis within the frontal plane. Laboratory results showed especially a hypokaliemia at 2.1 mEq/1. Digitalics withdrawal and kaliemia correction allowed the resolution of the tachycardia. The patient was treated with diuretics, Amiodarone and platelets antiaggregants. No further episodes of bidirectional tachycardia were observed