Bidirectional ventricular tachycardia associated with digoxin toxicity and with normal digoxin levels

Abstract

Introduction Bidirectional ventricular tachycardia (VT) is a regular tachyarrhythmia of ventricular focus with 2 different QRS morphologies alternating on a beat-to-beat basis. The rate typically is between 140 and 180 bpm, with a frontal plane axis varying between –201 to –301 and 1101. Causes of this rare arrhythmia are limited and include catecholaminergic polymorphic VT, digitalis toxicity, myocarditis, left ventricular hypertrophy, myocardial infarction, herbal aconite poisoning, familial hypokalemic periodic paralysis, and Andersen-Tawil syndrome. Recently, pulmonary embolism and pheochromocytoma have also been implicated in causing this arrhythmia. We present 2 cases of bidirectional VT attributable to digoxin, one of which had a significantly raised serum digoxin level and 1 within laboratory normal limits.