Accelerated idioventricular rhythm degenerating into bidirectional ventricular tachycardia following acute myocardial infarction.

Bidirectional ventricular tachycardia (BVT) is a rare ventricular tachyarrhythmia. It is usually regular, demonstrating a beat-to-beat alternation in the QRS frontal axis that varies between -20° to -30° and +110°. The tachycardia rate is typically between 140 and 180 beats/min and the QRS is relatively narrow, with a duration of 120 to 150 ms. The etiology of published BVT cases is most commonly digitalis toxicity and, rarely, herbal aconitine poisoning, hypokalemic periodic paralysis, catecholaminergic polymorphic ventricular tachycardia (CPVT), myocarditis, and Andersen-Tawil syndrome. We report a case of accelerated idioventricular rhythm (AIVR) degenerating into BVT following acute myocardial infarction, and briefly discuss the proposed mechanisms underlying BVT.