Echocardiography is used to assess the annular dimension and detailed anatomic characteristics of the aortic valve. Annular dimension is a key measurement. It determines eligibility for TAVI and guides the selection of valve type and size. It is measured in systole, in a parasternal long-axis view, zoomed on the left ventricular outflow tract. The measurement is taken at the point of insertion of the aortic valve cusps, from tissue blood interface to blood tissue interface - trailing edge to leading edge (Figure 3A), regardless of the degree of calcification of the aortic cusps.

Using the long-axis view (usually around 110-130°), the LVOT and upper septum should be assessed since the presence of a subaortic septal bulge may create an obstacle to proper seating of the aortic prosthesis23. In order to minimize the risk of coronary occlusion, it is essential to know the distance from the aortic annulus to the ostia of the coronary arteries and to compare this to the length of the cusps measured in a long-axis view. (Figure 4)

Measurement of the left coronary annular-ostial distance requires 3D TEE or MSCT.