Two ventricular tachycardias with cycle length and QRS alternans: insights into the mechanism from mapping and ablation of the tachycardias.

This case describes a patient with two separate foci of idiopathic ventricular tachycardia in the right ventricle. Both of the tachycardias manifested cycle length and QRS alternans. Both were successfully ablated and information from the electrophysiologic study and ablation procedure indicated that both tachycardias were focal, secondary to triggered activity, and that the best model to explain the cycle length and QRS alternans during tachycardia was that of "self-entraining modulated parasystole."