Eccentric electrical impulses became uniformly conducted across the transverse axis of canine bundle branches at 8-15 mm and false tendons at 2-4 mm, while premature stimulation caused longitudinal temporal dissociation.
This preclinical study demonstrates that transverse spread of impulses in the distal A-V conducting system involves propagation through transverse crossover points, with uniform conduction achieved at specific distances from the stimulus site.
Isolated preparations of portions of the canine intraventricular conducting system were studied by microelectrode techniques in order to determine the nature of transverse spread and longitudinal dissociation of impulses in bundle branches and false tendons. Driving stimuli were delivered to an eccentric location on normal conducting tissue, and the arrival times of the propagating impulses were mapped along the length and width of the bundle branch, or along the false tendon ipsilateral and contralateral to the site of stimulation. The difference between the arrival times on the two sides was found to decrease progressively as a function of distance from the site of stimulation, the data suggesting that transverse spread of impulses involves propagation through transverse crossover points between the longitudinally oriented conducting elements. Impulses originating eccentrically became uniformly conducted across the transverse axis of bundle branches 8-15 mm from the level of the stimulating electrode, and of false tendons 2-4 mm from the stimulus site. True longitudinal dissociation, producing conduction maps different from those representing normal transverse propagation, was seen occasionally in tissue having longitudinally oriented strips of abnormal tissue. However, early premature stimulation commonly resulted in longitudinal temporal dissociation of the premature responses, possibly due to functional block in the transverse crossover fibers.
Myerburg et al. (1973) studied Normal and abnormal canine intraventricular conducting system (n=48). Eccentric and premature electrical stimulation vs. Regular driven stimulation was evaluated on Distance required for uniform transverse conduction. Eccentric electrical impulses became uniformly conducted across the transverse axis of canine bundle branches at 8-15 mm and false tendons at 2-4 mm, while premature stimulation caused longitudinal temporal dissociation.