Editor’s Perspective: Bundles Branch Reentry

Abstract

Among the most memorable classic bedside teaching discussions in electrophysiology is the consideration of a narrow complex beat in a patient with fixed bundle branch block. The discussion would frequently extend to questioning how narrow complex tachycardias can arise from the ventricles. As in many aspects of medicine, exceptional cases serve to further understanding of fundamental concepts germane to frequently encountered arrhythmias. In this installment of the Teaching Rounds in Cardiac Electrophysiology, Kusa et al1 continue this educational tradition by guiding us through an intriguing case of ventricular tachycardia (VT) with multiple morphologies that was successfully ablated at a single location. They teach us about the need to think imaginatively, yet logically, when considering the components of the infra-Hisian conduction system that may participate in tachycardia. After combining insight and electrogram analysis and excluding some candidate possibilities, they hypothesize one possible explanation for their findings and success with ablation of the right bundle branch. Article see p e87 A commonly asked question is whether the H-V interval measured during bundle branch reentrant VT is shorter or longer than the H-V interval measured in sinus rhythm. Figure A illustrates the important distinction between true and pseudo-intervals in electrophysiology. The H-V interval in sinus rhythm is a true conduction interval with conduction passing through the region of the recording electrodes near the His bundle and then exiting to the ventricles through the distal bundle branches such that it truly reflects the conduction time from His depolarization to ventricular activation. However, during typical bundle branch reentry, conduction proceeds from a common branch point (marked as A) to the His and concurrently down the right bundle toward the ventricular exit. Thus, there is no actual linear conduction from the His to the V but rather from a common branch point to both of …