Effects of the site and timing of atrioventricular nodal input on atrioventricular conduction in the isolated perfused rabbit heart.

Programmed stimulation was used to study patterns of atrioventricular nodal propagation in an isolated rabbit heart preparation. Stimulation was done at the two major atrioventricular nodal input regions, the crista terminalis and interatrial septum, by use of various sequencing protocols. The influence of stimulation input interactions on atrioventricular nodal propagation was then evaluated with the use of simultaneous extracellular and intracellular recordings from the various regions of the atrioventricular node and His bundle. Activation of the atrioventricular node occurred predominantly via the stimulated input site, although perinodal conduction to the opposite input also occurred and could modify the atrioventricular conduction pattern. Engagement patterns of both AN and N fibers were dependent on the sequence of activation at the major input sites, and similar conduction times to the His bundle were often associated with different local activation times, depending on the site of premature stimul...