Dissociation and delayed conduction in the canine right bundle branch.

Abstract

Bipolar electrograms were recorded from five to six sites on the septal right bundle branch (RBB) using a multielectrode patch in ten mongrel dogs. Antegrade activation was recorded along the right bundle during sinus rhythm and during right atrial pacing at varying heart rates. Retrograde activation was produced by pacing from right ventricular epicardium. Right bundle conduction velocities varied from 1.4 to 3.3 m/sec (mean 2.0 m/sec) for antegrade conduction and from 1.8 to 2.7 m/sec (mean 2.1 m/sec) for retrograde activation. Varying degrees of conduction delay were elicited by premature stimulation and mechanical pressure to the right bundle. The conduction delays occurred over small segments of the right bundle branch with regeneration of normal propagation velocity distal to the region of block. The conduction delays were associated with fragmentation of the RBB electograms with initiation of delayed activation waves which traveled variable distances antegrade and retrograde. These data show that stress-induced longitudinal dissociation may produce delayed activation waves within the right bundle branch which may simulate re-entrant arrhythmias.