Facilitation of sustained bundle branch reentry by atrial fibrillation

An electrophysiologic evaluation was performed in a patient with an idiopathic dilated cardiomyopathy and syncope. Ventricular tachycardia was not inducible despite the use of a variety of pacing maneuvers during sinus rhythm. Only after the electrical induction of atrial fibrillation did sustained bundle branch reentrant tachycardia (with both right and left bundle branch block QRS configurations) spontaneously occur and become reproducibly induced during right ventricular pacing. Ablation of the right bundle branch eliminated reproducibility of the tachycardia.