Aortic annulus

In traditionnal litterature, the fibrous aortic annulus refers to the portion of the fibrous skeleton of the heart of the aortic valve that provide structural support, particularly at the noncoronary aortic sinus and parts of the right and left coronary sinuses, and are continuous with the left and right fibrous trigones

But in nowadays, the aortic annulus is considered as a virtual ring defined by joining the basal attachments (nadirs) of the three aortic valve leaflets, forming the boundary between the left ventricular outflow tract and the aortic root. It is not a true anatomical structure, but rather a functional and imaging construct used for clinical and procedural purposes, especially in valve sizing for transcatheter aortic valve replacement (TAVR) and echocardiographic assessment.