Aortic root diameters

Anatomy of the Aortic Valvar Complex

Normalized diameters for the dynamic aortic root vary among the age groups. There are apparent relationships between the dynamic diameters and age, body surface area, weight, and height of the patient.

The shape of the aortic root is consistent, though its diameter can vary considerably. The diameter at its outlet, which is the level of the sinotubular junction, exceeds that at the level of its inlet at the virtual ring formed by the basal attachments of the leaflets by a ratio of 1.34 to 1¹⁴. Thus, the root has been described as a truncated cone. Importantly, the valvar complex is a dynamic structure, and its dimensions change according to the phases of the cardiac cycle and with changes in pressure within the aortic root^15, 16. The diameter of its entrance, the so-called aortic annulus, in particular, increases in diameter and decreases in eccentricity during ventricular systole (Prosthesis size).

Accurate measurement of the dimensions of the root is a critical component of successful TAVI. Erroneous measurement of the aortic root (Figure 14) can lead to malposition or embolisation of the prosthesis, paravalvular leak, rupture of the entrance to the root, and the potential for an early structural degeneration of the prosthesis leaflets. Several imaging modalities can be used for assessing the dimensions of the so-called annulus (Prosthesis size). The measurements of relevance include¹⁷:

• Annulus dimensions: maximal, minimal, and mean diameter, area, perimeter (circumference)
• Diameter of the Sinuses of Valsalva
• Height of the Sinuses of Valsalva
• Coronary artery height of the coronary arteries
• Diameter of sinotubular junction and ascending aorta

Erroneous measurement of the diameters of the root

This basal short-axis view shows the closed aortic valve. The arrows demonstrate the potential hazard of two-dimensional imaging techniques (echocardiography, contrast aortography) for measuring the "aortic valve annulus". Measurements made using the basal attachment of the leaflets do not transect the full diameter of the outflow tract but instead, a tangent cut across the root.