What is the atrioventricular node? Some clues in sorting out its structure-function relationship.

The anatomic and functional substrate underlying AV nodal rate-dependent and dual pathway properties remains highly controversial. This article focuses on some factors that impair the understanding of the AV nodal structure-function relationship and some clues toward sorting it out. A definition of the AV node that applies to both anatomic and functional studies, an orthogonal topographic representation of nodal structures, and the integration of rate-dependent and dual pathway behavior of the AV node are proposed as primary steps toward a better understanding of the AV nodal structure-function relationship. Further fact-based information is the key to the sorting out of this puzzle.