Transverse interconnection
Song-Yun Chu et al. describing the LBBP as a choice to correct the RBBB
in a case report putting forward an intriguing theory that unipolar
pacing captured the intra-Hisian LBB then recruited the distal RBB
through transverse interconnection fibers (TF). TF, connecting the left
and right bundle branches, can transmit the electrical signals from LBB
to RBB, thus correcting the distal RBBB and causing a narrower QRS
complex 17. (Figure 3 C) Back in the 1970s, Lazzara et
al. stimulated the incised His bundle intracellularly and found that the
native conduction restored, which suggested that functional transverse
interconnection (FTI) exists in the His bundle and the bundle branches
and can transmit an electrical signal across fibers18. Transverse interconnection challenges the
traditional theory of longitudinal dissociation that the LBB and RBB are
longitudinally separated by collagen sheaths within the His bundle,
making conduction better “end to end” than “side to side” within the
His bundle. 19. The limitation of transverse
interconnection has been noticed before, if transverse connections
coexist with longitudinal dissociation, then the native conduction would
circumnavigate the structure block 20. We suspected
that if there is indeed a transverse connection between bundle branches,
the excitation generated by LBBP would bypass the block to RBB and then
conduct forward through RBB and Purkinje fibers to excite the RV with no
paced morphology of RBBB pattern. Besides that, the anatomical structure
of these fibers has not been clearly reported before, which requires
further studies, especially in the human body 21.