Description and Example:
To calculate Aortic Valve Area by the continuity equation you need the following:
1) LVOT diameter from the PLAX view (in most people this is near 2 cm). This is assumed to be constant throughout systole.
2) LVOT velocity and/or VTI from the 5 chamber or apical long axis view.
3) The velocity of VTI at the aortic valve from the 5 chamber or apical long axis view.
By the continuity Equation: Area1xVTI1 = Area2x VTI2
LVOT Area x LVOT VTI = AV Area x AV VTI 3.14(2.0cm/2)2 x 19cm = AV Area x 82.1cm AV area =
Area = 0.72cm2, which along with the high mean gradient and peak jet velocity is consistent with severe aortic stenosis.