Functional Bundle Branch Block as a Delayed Manifestation of Retrograde Concealment in the His‐Purkinje System

Abstract

These observations suggest that the type of functional bundle branch block occurring in the second SVT complex as a de novo phenomenon may be related to the relative timing of the retrograde penetration of the right versus left bundle during ventricular pacing or bundle branch reentrant complex. Therefore, due to its longest cycle length of activation and refractoriness, the earliest site of retrograde penetration is the most likely site of functional block during propagation of the second SVT complex. This delayed manifestation of retrograde concealment may provide new information regarding the electrophysiologic behavior of the His-Purkinje system.

Effects of right bundle branch block during atrioventricular nodal reentrant tachycardia

“…In the present study, transient RBBB occurred after introducing a short burst of right ventricular pacing; these findings suggested that the retrograde concealment of ventricular impulses in the His-Purkinje might account for the occurrence of transient RBBB [2,5]. Li et al used a quantitative model to demonstrate that the lower turnaround point of AVNRT circuit was above the His-bundle in more than half of the 70 patients with AVNRT [15].…”

“…This phenomenon occurs much more frequently during orthodromic reentrant tachycardia than AV nodal reentrant tachycardia (AVNRT) [1][2][3][4][5]. To our knowledge, few studies have reported the effects of bundle branch block during AVNRT.…”

Atrioventricular Nodal Reentrant Tachycardia: Current Understanding and Controversies

“…Similar to other types of SVT, functional right BBB is the most common functional BBB in AVNRT. Multiple mechanisms may be operative in the genesis of functional BBB [10,11]. Of these, the long-to-short (H-H) CL variation of the antegrade inputs into the HPS is the most prominent one.…”

“…At first glance, because of irregular ventricular responses, this SVT may appear as atrial tachycardia. Note that the QRS complexes exhibit narrow complex morphology (1, 3, 5, 7 and 9), functional right bundle branch block (2, 6 and 8), or functional left bundle branch block (10 (Continued) Panel (c) is a magnified version of a portion of panel (b)showing only six QRS complexes(6)(7)(8)(9)(10)(11). The atrial (A e -A e ) CLs show minimal variability.…”

“…However, each A e -A e cycle is preceded by an identical His bundle activation (H-H) CL, favoring the diagnosis of typical AVNRT. Also, it should be noted that, as shown in the ladder diagram, the site of AV block is in the His-Purkinje system, exhibiting functional Wenckebach periodicity until 1:1 AV conduction resumes with functional left bundle branch block(10)(11)(12). Panels (d) and (e), obtained from a third patient, show two episodes of SVT with either variable AV blocks (panel d) or 1:1 AV conduction.…”