Anatomical characterisation of an additional atrioventricular node artery contributing to the arterial complex of proximal conduction components: Bonapace’s septal branch or Kugel’s collateral artery

Background Transient or permanent iatrogenic conduction disturbances from injury to arteries supplying the cardiac conduction system (CCS) have increased. A more comprehensive understanding of CCS arterial anatomy is essential for advancing electrophysiological studies. Compared with the sinus node (SN) artery, atrioventricular node (AVN) artery is more variable and difficult to identify because of the thicker surrounding myocardium. Arterial sources other than the main AVN artery branching near the cardiac crux—such as the Bonapace’s septal branch or Kugel’s collateral artery—have often been overlooked or regarded as atypical and remain poorly characterised. Methods An alternative origin and course of the AVN artery were examined in 116 hearts via microdissection and in 14 additional hearts using serial histological sections of physiologically aged hearts without coronary artery occlusion. Results An additional descending AVN artery was observed in 22.4% of cases and an interatrial septal branch extending to Koch’s triangle was found in 11.2% based on the macroscopic analysis—findings aligning well with the histologically verified incidence of 35.7%. These results suggest that approximately one-third of individuals exhibit an additional descending AVN artery with features resembling the normal Bonapace’s septal branch. Notably, this additional artery originates from a common trunk with the SN artery and Bachmann’s bundle branches, forming an arterial complex supplying the proximal conduction components. Conclusions Using a large sample size, our findings highlight the anatomical and clinical importance of the arterial complex supplying the proximal conduction components, including the additional descending AVN artery. This arterial complex may include the Bonapace’s septal branch and serve as a Kugel’s collateral route in coronary occlusion. This characterisation provides basic essential anatomical data to support future research on iatrogenic conduction disturbances.