LINKING
Whenever 2 discrete pathways of conduction exist, impulses in one can influence the conduction
properties of the other. The onset of this phenomenon seems to be related to the FRP of the FP.

Mechanism of linking:
1-Persistent retrograde functional conduction delays in the HPS during RV pacing
2-Antegrade Kent bundles at rapid rates dependent on a prior block in the normal pathway
3-Persistent antegrade functional infra-His block of atrial impulses during RV pacing
4-Transient advancement of His activation with ventricular fusion complexes during overdrive
ventricular pacing of BBRT.

The linking phenomenon has many variations because of the many types of macroreentrant
tachycardia found in humans

                                    
                                                    
Linking phenomenon in dual AVN pathways - Jpn Circ 2001

Antegrade conduction block in one pathway as well as subsequent concealed retrograde
conduction of impulses in the other pathway causes the linking phenomenon
Persistence of LBBB aberrancy is typical for transseptal concealed conduction.
A conducts down the RBBB and blocks in the LBBB. Then transseptal conduction (concealed) occurs
from the right to left ventricle with retrograde invasion of the impulse into the distal left bundle branch.
This relatively late activation of the LBB will prolong its refractoriness compared with the RBB. When
the next SVT impulse arrives at the LBB it will be refractory and block occurs. A similar scenario can
occur with persistent RBBB aberrancy due to retrograde invasion from the LBB transseptally into the
distal RBB.

Peeling back of refractoriness: a PVC at a critical time interval can result in termination of the
transseptal concealed conduction. The PVC peels back the RP of the LBB by preventing the impulse
from activating it at its usual later time.