Obtain a Zoomed CFD of the AV in the mid Transgastric or Deep Transgastric view.If there is a sufficiently stenosed aortic valve, a PISA formation will occur. The distance from the center of the PISA formation to it's first aliasing velocity edge (where the color shifts from blue to red) is the radius of the PISA formation.
Note the aliasing velocity. The aliasing velocity is the velocity where if the flow exceeds this velocity the flow will be displayed with colors from the opposite scale.
Obtain a continuous wave doppler (CWD) of the aortic valve. The CWD of the aortic valve will yield a flow profile where, utilizing the calipers (or you can trace it) to show the peak velocity. The peak velocity is the Vmax which is typically 5 m/sec.
Obtain an angle of the PISA formation: The angle at the aortic valve is typically 180 degrees, whereas the angle at the mitral valve (for mitral stenosis calculations) is typically 120 degrees.
Determine the LVEF and enter the above data. The degree of aortic stenosis can then be calculated.