The term "A-V junctional" has replaced "A-V nodal" in recent years, owing to sound arguments voiced by many researchers. A brief review of recent anatomic and electrophysiologic data is necessary to explain this change, since the substitution transcends a simple semantic decree.1
The A-V node lies at the base of the interatrial septum between the coronary sinus and the medial tricuspid valve leaflet. It connects to the sinus node by three distinct anatomic pathways which may provide a functional route for rapid transmission of the sinus impulse through the atria to the A-V node.2 In addition to these internodal pathways, anatomically distinct pathways bypassing all or part of the A-V node have been implicated in the interpretation of a number of electrocardiographic phenomena,3 and will be discussed in the future.
Past teaching has indicated that the site of the pacemaker focus during nodal beats lay within the