The morphological significance of the human sinuatrial nodal branch (artery).

The sinuatrial nodal branch/artery (SANB), the sinuatrial nodal branch of the coronary artery, is anatomically regarded as a significant artery since it is used as a landmark to identify the sinuatrial node, in addition to its clinical significance. In previous reports, the SANB has been shown to have 2-5 routes and it had only one branch in 91%-100% of hearts. These results indicate that compensation for the SANB is not possible in the case of its being cut or occluded. Therefore, we macroscopically reinvestigated the SANB using 106 human adult hearts to obtain a detailed understanding of its morphology. The following results and discussions were obtained from our study. (1) The SANB was observed to take six routes and two or more branches were found in 57 out of 106 cases (53.7%). (2) In those cases in which the SANB had only one branch (46.3%), it was observed to be the result of forming the proximal arterial loop in 25 cases (51.0%). The total of these cases with one branch with the proximal arterial loop between the right and left coronary arteries and those with two or more branches were 82 cases (77.4%). These results strongly suggest that compensation for the SANB could occur in the majority of cases. (3) We speculated that the SANB was generated by the disappearance of and the anastomosis between the lateral arterial loop, lateral to both auricles, and the medial arterial loop, medial to both auricles.