Morphofunctional considerations on the atrioventricular node arterial vascularization

The atrioventricular node (AVN) is the relay station for electrical impulses passing from the atria to the ventricles. The arterial resources of the AVN are functionally relevant and may be interfered by various surgical procedures which deal with the cardiac valves. Our study aim to bring detailed evidences on the arterial supply of the AVN. We dissected and microdissected 50 human adult hearts without any known history or evident cardiac pathology, in order to evidence the arterial suppliers of the AVN; subepicardial dissections were continued in the interatrial septum (the triangle of Koch). We were able to define 5 morphological types (each with distinctive subtypes) of the atrioventricular node artery (AVNA) emerged at crux cordis: type I (22%, AVNA from the U-turn of the right coronary artery (RCA), the left retroventricular artery (RVA) absent), type II (18%, AVNA from PIVA, left RVA present), type III (34%, AVNA from the left RVA, PIVA from the RCA), type IV (AVNA from the bifurcation of the RCA into the PIVA and the left RVA – trifurcated RCA) and type V (AVNA from the circumflex artery). In 18% of specimens we found duplicated AVNA. In 22% of specimens, the AVN area was additionally supplied by the descending septal artery (right descending superior artery) originating from the sinoatrial artery, on the right side of the aorta. The origin of the AVNA, which is variable, and the accessory resources, such as the descending septal artery, can explain the possible individual occurrences of the cardiac rhythm alterations determined by coronary ischemia. Our AVNA types are all related to the atrioventricular and aortic valves and thus liable to damage during specific surgical procedures, interfering with the respective valves. Duplicated AVNAs must be kept in mind during the selective atrioventricular nodal artery catheterizations and AVNA must be evaluated angiographically prior to the interventions. Our study demonstrates that classical dissections combined with microdissections can still offer valuable informations for a pathologist assigning not only the mechanisms but also the morphological conditions of the cardiac arrest. A seek and search investigation is launched in every sudden cardiac death: the forensic pathologist make a good team with the anatomist retrieving very useful etiological data.