Anatomy and physiology of the atrioventricular node: What do we know today?

Abstract

Atrioventricular (AV) node consists of a part of the sole pathway of impulse conduction from the atria to the ventricles. It becomes the base of occurrence and maintenance of various arrhythmias involving this region by special electrophysiological characters as follows: The conduction across the node is quite slow, it functions as two separated conductors with property of fast or slow conduction, and it has the automaticity. AV junctional area including the node itself potentially works as the ectopic center of a subsidiary pacemaker when the sinus node as the primary pacemaker fails to control the cardiac rhythm. Muscular bundles consisting of dual AV pathways are not anatomically distinguished but can be functionally differentiated by the difference of conduction property and refractoriness. A fast pathway connects with the center of the node from anterior part of interatrial septum, and a slow pathway does from posteroinferior area to the tricuspid valve. In cells of slow pathway, the occurrence of automaticity is determined and the expression of ion channels is similar to ones in the center of the node. These facts suggest that the dual-pathway physiology of the AV node is not only formed by special electrophysiological property of cells but based on the morphology.