Measure the Diameter of the LVOT. The diameter can be of the LVOT should be obtained from the midesophageal AVLAX view, in mid systole, and under the zoom mode. The view of the LVOT should not be an obtuse angle view. The aortic valve leaflets (NCC and RCC) should be clearly seen. The zoom mode will decrease the error present in the calculation. Since the LVOT diameter changes throughout systole, the mid systole measurement should be obtained.
Obtain a VTI of the LVOT. The VIT of the LVOT is obtained from a PWD of the LVOT. The PWD of the LVOT should be obtained at the same location as the LVOT diameter measurement. The PWD beam should not be off more than 15 degrees from parallel to the LVOT flow. After tracing the flow on the echocardiographic machine, a VTI of the PWD tracing will be calculated. A continuous wave doppler (CWD) of the LVOT could be obtained, but, since the CWD introduces ambiguity into the equation and since flows in the LVOT rarely exceed the aliasing velocity of the pulse wave doppler, PWD is the best measurement mode.