Alternans during fascicular ventricular tachycardia due to digitalis toxicity.

This report describes a digitalis-induced regular fascicular ventricular tachycardia characterized by marked QRS alternans a manifestation not usually associated with this arrhythmia. The striking alternation of QRS configuration suggested alternating ventricular activation from either a single focus with two exits in distal branches of the left anterior fascicle or 2 different foci localized in the Purkinje-myocardial network of the left anterior fascicle.