 Stroke volume = 0.785 x Diameter2 x VTI of LVOT

Cross sectional area of LVOT = 0.785 x LVOT Diameter2

formula_1

The weakest aspect of this calculation is the variability in measurement of LVOT area, because it involves squaring the LVOT dimension.Therefore, it is crucial for the sonographer to take great care in measuring the LVOT diameter.The measurement using echocardiogram may be inaccurate in cases of Aortic subvalvular stenosis, because there is not a uniform diameter, as assumed during echocardiogram.