Arthur Keith Was the First to Describe What Is Now Known as Koch’s Triangle: The Building of the Triangular Locus of the Atrioventricular Node from Todaro to Tandler

Purpose: To show the developments that culminated with the eponym Koch’s triangle -- the fibrous attachment of septal tricuspid leaflet, aperture of the coronary sinus and the tendon linking the inferior vena cava valve to the central fibrous body- and how it was a construct of several anatomists. Methods: The literature is reviewed centering in the discovery of the atrioventricular node by Sunao Tawara (January 1906), its previous announcement by Tawara’s mentor Ludwig Aschoff (1905) as well as in the contributions of the authors that described the other components of the triangular locus. Results :Tawara described the atrioventricular node and its relations with fibrous attachment of septal tricuspid leaflet and ostium of the coronary sinus. The first description assembling all components was due to Arthur Keith (March1906). Keith was also the first to consider the triangular locus as useful landmark for identifying the atrial structures of the conduction system discovered by Tawara and Wilhelm His Jr (1893).. Conclusion: The triangular locus of the atrioventricular node was a construct of several exceptional anatomists: The contributions of keith in this topic has been particularly overlooked. The triangular locus of atrioventricular node or triangle of atrioventricular node are more instructive and impartial names.