CASE REPORTS Bundle Branch Reentry: A Possible Mechanism

SUMMARY Electrophysiologic studies were performed in three patients suffering from attacks of parox-ysmal tachycardia with wide QRS complexes. Two patients had atrioventricular dissociation. The arrhyth-mia could be initiated and terminated by premature ventricular stimulation in all three patients. One patient developed the arrhythmia after rapid atrial stimulation. In each subject, the QRS complexes during tachycardia were identical to recorded supraventricular beats (left bundle branch block pattern in two cases and right bundle branch block pattern in one). A His bundle potential was noted before the QRS complex; the HV interval was equal to or longer than that of the sinus beats. The following observations suggested the presence of a bundle branch reentry mechanism: (1) the relationship between bundle branch block development and tachycardia initiation; (2) the occurrence of tachycardia after electrically induced His-Purkinje reentry; (3) the ability of premature ventricular stimulation during tachycardia to advance the timing of the His deflection and QRS complex, with an unchanged or slightly increased HV interval; and (4) the termination of arrhythmia by premature ventricular depolarization blocked within the bundle branch system. Our results support the idea that bundle branch reentry can play a role in the genesis of ventricular tachycardia. MOST paroxysmal tachycardias, both supraventricu