Linking: a dynamic electrophysiologic phenomenon in macroreentry circuits.

The term "linking" has been used specifically to describe the mechanism for perpetuation of functional anterograde bundle branch block: namely, repetitive transseptal retrograde concealed penetration by impulses propagating along the contralateral bundle. We present selected examples that demonstrate tht linking-type phenomena actually have a wide spectrum of expression in human macroreentry circuits, particularly those incorporating either the bundle branches and His bundle or the normal pathway and Kent bundle. The examples presented are as follows: (1) persistent retrograde functional conduction delays in the His-Purkinje system during right ventricular pacing, (2) anterograde Kent bundle condution at rapid rates, dependent on prior block in the normal pathway, (3) persistent anterograde functional infra-His block of atrial impulses during rapid ventricular pacing in the presence of a retrogradely conducting accessory pathway, and (4) transient advancement of His activation with ventricular fusion complexes during overdrive ventricular pacing of bundle branch reentrant tachycardia. Based on these examples, we characterize linking as a generalized electrophysiologic phenomenon in which each successive impulse entering a macroreentry circuit propagates preferentially along one limb because of functional block in the contralateral limb resulting from the effects of the prior impulse. It is proposed that such functional block may be dynamically maintained either by repetitive impulse interference, which perpetuates local refractoriness (examples No. 1 to 3), or by repetitive impulse collision (example No. 4). The general conceptual scheme outlined can be applied to specific electrophysiologic phenomena associated with a wide variety of reentry circuits in man.