Editor’s Perspective: Bundles Branch Reentry

Incessant tachycardia in a patient with advanced heart failure and left ventricular assist device: What is the mechanism?

“…These observations suggest that activation during tachycardia propagates retrograde through right bundle branch and then activates the ventricles antegrade through the conduction system (left fascicle). A shorter HV interval during tachycardia compared to sinus rhythm is consistent with activation simultaneously propagating from the takeoff of the left fascicle in either direction (up the bundle of His and down the left bundle branch to generate the QRS) [1] , [2] . The similar QRS morphology of conducted sinus beats ( Fig.…”

“…1 C, the HV interval during the tachycardia (60 msec) is shorter than the HV interval with a conducted atrial beat (88 msec). Compared to the actual HV conduction interval with sequential activation of His followed by V during sinus rhythm, a shorter HV during tachycardia suggests activation of His and V occurring in parallel from a common intervening site [1] , [2] . This finding excludes supraventricular tachycardias with antegrade activation of the His-bundle (e.g.…”

84-year-old woman with dizziness

“…2 In bundle branch re-entry, classically, the circuit conducts antegrade via the right bundle and retrograde via the left, giving a narrowed QRS but a typical bundle branch block pattern. 3 This tends to be an LBBB, but in this case, it is a right bundle branch block with a rightward axis, suggesting a VT originating in the anterior fascicle. An electrophysiological study would make the diagnosis certain; however, the patient declined.…”

Bundle branch reentry with His dissociation—The His bundle: Bystander or participant?

“…Although a consistent His-RB/ventricular activation sequence is a diagnostic criterion for BBR that distinguishes it from other VT, theoretically it is possible to dissociate the entire His segment superior to the turnaround point (TP), which does not participate in the reentry circuit. 6 …”