Abstract 13172: Transverse Versus Longitudinal Electrical Propagation Within the Atrioventricular Node During Dual Pathway Conduction
Introduction: We have discovered and validated that AV node dual pathway conduction results in His electrogram alternans (HEA), which indicates dual inputs instead of a final common pathway from AV node into the His bundle. We hypothesized that fast pathway (FP) propagates in a direction across AV nodal fibers orientation, while slow pathway (SP) propagates longitudinally along fibers orientation. This transverse versus longitudinal propagation results in functional dissociation in distal node and dual inputs into the His bundle.
Methods: Action potentials (AP) from multiple locations in the superior and inferior AV nodal domains were obtained to monitor electrical propagation during A1A2 programmed pacing in 8 rabbit hearts. Dual pathway conduction was confirmed by HEA.
Results: AV nodal fibers were generally aligned longitudinally along the AV conduction axis. During FP conduction at basic beat A1, electrical excitation propagated in a superior to inferior direction across major fibers orientation (Figure, inset). In contrast, during SP conduction at premature beat A2, the superior-inferior propagation failed within superior nodal domain, permitting electrical propagation to proceed in inferior nodal domain along fibers orientation in a posterior to anterior direction. As a result, FP activated first the superior distal node (Figure, earlier superior NH AP [SNH] at A1). In contrast, SP activates first the inferior distal node (earlier inferior NH AP [INH] at A2). This functional dissociation of superior-fast and inferior-slow domains in distal node produced early-and-high superior His electrogram (SHE) by FP and early-and-high inferior His electrogram (IHE) by SP (Figure), characterized as HEA.
Conclusions: Transverse versus longitudinal electrical propagation within the AV node produces functional dissociation in the distal node, resulting in superior-fast and inferior-slow inputs into the His bundle and HEA during dual pathway conduction.
- © 2013 by American Heart Association, Inc.