AUTHOR=Zhang Youhua 

TITLE=A jump in the atrioventricular conduction curve is not caused by a switch from fast pathway to slow pathway conduction

JOURNAL=Frontiers in Physiology

VOLUME=15

YEAR=2024

URL=https://www.frontiersin.org/journals/physiology/articles/10.3389/fphys.2024.1367509

DOI=10.3389/fphys.2024.1367509

ISSN=1664-042X

ABSTRACT=<p><bold>Background:</bold> A jump in the atrioventricular (AV) conduction curve is the current clinical criterion of dual-pathway electrophysiology. However, the assumption that a jump indicates a switch from fast pathway (FP) to slow pathway (SP) conduction remains unconfirmed. This study was carried out to investigate whether a jump indeed indicates a transition from FP to SP conduction, and if not, what the potential cause is.</p><p><bold>Methods:</bold> Eighty-one experimental records from rabbit AV nodal preparations containing the following data were analyzed: 1) had at least one AV conduction curve and 2) had recording of His electrogram alternans (a validated new index of dual-pathway conduction). Most cases also had intracellular action potential recordings from the AV nodal fibers.</p><p><bold>Results:</bold> Of the 81 preparations, 11 (13%) showed a jump in the AV conduction curve. The jumps always occurred after the FP to SP transition. The FP–SP transition occurred at prematurity at 196 ± 39 ms <italic>versus</italic> the jump at 114 ± 13 ms (<italic>p</italic> &lt; 0.001). The beat with a jump showed an SP–FP pattern in seven and an SP–SP pattern in four preparations. The jumps were always associated with and most likely caused by the formation of intranodal/nodal–atrial reentry and its subsequent conduction, rather than a switch from FP to SP conduction.</p><p><bold>Conclusion:</bold> Contrary to what has been assumed, a transition from FP to SP conduction does not produce a jump in the AV conduction curve. A jump in the AV conduction curve is most likely caused by the formation of intranodal/nodal–atrial reentry and its subsequent conduction.</p>