[Topographical anatomy of the atrioventricular node of Tawara--findings by macro-microscopic dissection under...

The atrioventricular node of Tawara was dissected macroscopically under dissecting microscope with scalpel and microforceps. The node is a flat and fan-shape mass of the specialized cardiac muscular tissue, which is sandwiched between the floor of the right atrium and the right fibrous trigone as an epi- or extra-myocardial structure, in the center of the heart as a whole. The node is situated in the apical (anterior) angle of the triangle of Koch, and does not show any individual variation in its location, occupying the same site topographically. Orifice of the coronary sinus is not proper to indicate the location of the node, because orifice of the coronary sinus changes its position individually. Clinically, the location of the node can be presumed correctly by identifying the important anatomical landmarks; postero-inferior angle of the membranous portion of the interventricular septum, commissure between the septal and the accessory (or anterior) cusps of the tricuspid valve, attachment line of the septal cusp, and the tendon of Todaro.