Inferior Extensions of the Atrioventricular Node.

The pathways for excitation of the atrioventricular node enter either superiorly, as the so-called 'fast' pathway, or inferiorly as the 'slow' pathway. However, knowledge of the specific anatomical details of these pathways is limited. Most of the experimental studies that established the existence of these pathways were conducted in mammalian hearts, which have subtle differences to human hearts.