CLINICAL ANATOMY OF THE ATRIOVENTRICULAR JUNCTIONS

Objectives. This study reevaluated the anatomy of the areas anterior a nd posterior to the atrioventricular (AV) septal structures, previousl y said to represent anterior and posterior septal areas. Background. I n descriptions of the locations of accessory AV pathways within the AV junctions, four regions have been recognized: the left and right free walls and the anterior and posterior septums. On the basis of known f acts concerning cardiac structure, it is questionable whether these so -called septums are truly septal. Methods. Ten human hearts were disse cted to elucidate the clinical anatomy of these purportedly septal reg ions, together with the overall arrangement of the AV junctions. Resul ts. The true septal components of the AV junctions are the muscular an d membranous AV septal areas. These separate the cavity of the right a trium from that of the left ventricle. The region previously designate d as the anterior septum is part of the right parietal junction. It is contiguous with the membranous part of the septum but extends anterio rly and laterally from the septum as part of the supraventricular cres t of the right ventricle (''crista supraventricularis''). In the regio n posterior to and beneath the mouth of the coronary sinus, only the m ost anterior extent, in continuity with the central fibrous body, is p art of the muscular AV septum. The posterior extent of this area roofs over the diverging right and left ventricular walls and is filled in with fibroareolar tissue of the AV groove. Conclusions. The larger par t of the regions anterior and posterior to the true AV septal areas ar e not septal but are parts of the parietal AV junctions. An understand ing of these anatomic relations is essential for those wishing to modi fy conduction across the AV junctions.