A possible role of the specialized conduction system in the conversion of ventricular tachycardia to ventricular fibrillation.

Electrode recordings from the right bundle branch, His bundle, and right atrium in a canine preparation enabled us to observe the activation of the ventricular myocardium and the specialized conduction system during the conversion of ventricular tachycardia to ventricular fibrillation. At times when ventricular tachycardia degenerated to ventricular fibrillation, asynchronous activation of the right bundle branch and the ventricular myocardium was frequently noted. Such asynchrony of activation was not seen during the spontaneous conversion of ventricular tachycardia to sinus rhythm. We suggest that this asynchronous activity produces increasing fractionation of ventricular activation fronts, which in turn yields fibrillation.