Relationship between the aortic root and the atrioventricular conduction axis

Damage to the atrioventricular conduction axis continues to be a problem subsequent to transcatheter implantation of aortic valvar prostheses. Accurate knowledge of the precise relationships of the conduction axis relative to the aortic root could greatly reduce the risk of such problems. Current diagrams highlighting these relationships rightly focus on the membranous septum. The current depictions, however, overlook a potentially important relationship between the superior fascicle of the left bundle branch and the nadir of the semilunar hinge of the right coronary leaflet of the aortic valve. Recent histological investigations demonstrate, in many instances, a very close relationship between the left bundle branch and the right coronary aortic leaflet. The findings also highlight two additional variable features, which can be revealed by clinical imaging. The first of these is the extent of an inferoseptal recess of the left ventricular outflow tract. The second is the extent of rotation of the aortic root within the base of the left ventricle. Much more of the conduction axis is within the confines of the circumference of the outflow tract when the root is rotated in counterclockwise fashion as assessed from the perspective of the imager, with this finding itself associated with a much narrower inferoseptal recess. A clear understanding of the marked variability within the aortic root is key to avoiding future problems with atrioventricular conduction.