Role of the perinodal region in atrioventricular nodal reentry: evidence in an isolated rabbit heart preparation.

To evaluate the role of perinodal tissue in the genesis of atrioventricular (AV) nodal reentry, echo beats were induced by programmed stimulation in nine superfused rabbit atrial-atrioventricular nodal preparations. In these preparations, extracellular bipolar electrograms were recorded simultaneously from the crista terminalis, interatrial septum arid His bundle, along with microelectrode action potentials from cells in the AV node and perinodal tissues. Three patterns of AV reentry were observed: 1) In four preparations, with the introduction of basic and premature stimuli at the crista terminalis input region to the AV node, block occurred within the AV node, anterograde conduction continued along the perinodal fibers and entered the AV node by way of the interatrial septal input region. Reentry occurred via retrograde nodal conduction. 2) In two other preparations, with the introduction of basic and premature stimuli at the interatrial septal input region, conduction blocked