ANATOMY: Clinical anatomy of the aortic root

The aortic valve, and its supporting ventricular structures, form the centrepiece of the heart. All chambers of the heart are related directly to the valve, and its leaflets are incorporated directly into the cardiac skeleton. As such, the valve is the focus for the echocardiographer. Yet still the precise structure of its component parts remains controversial, with persisting disagreements relating largely to the enigmatic “annulus”. Indeed, it is difficult to find an unequivocal definition of the annulus, a structure appearing most frequently in the context of cardiac surgery.1 This review describes the arrangement of the aortic root in terms of the attachment of the aortic valvar leaflets, and their relations to the aorta and its ventricular support.2 Recognising that these parts will still be considered to represent an annulus, I will try to show that the ring like structure thus described has considerable length, encompassing the entirety of the semilunar attachments of the leaflets. It is the recognition of the relation of these attachments to the anatomic and haemodynamic ventriculo-arterial junctions which is the key to understanding.3 Although forming the outlet from the left ventricle, when viewed in the context of the heart as it lies within the chest (“attitudinally correct orientation”4), the aortic root is positioned to the right and posterior relative to the subpulmonary infundibulum (fig 1). The subpulmonary infundibulum is a complete muscular funnel which supports in uniform fashion the leaflets of the pulmonary valve.5 In contrast, the leaflets of the aortic valve are attached only in part to the muscular walls of the left ventricle. This is because the aortic and mitral valvar orifices are fitted alongside each other within the circular short axis profile of the left ventricle, as compared to the tricuspid and pulmonary valves which occupy opposite ends …