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Aortic Valve Area Calculator

Although our website is focused on the electrocardiogram, after receiving requests from several colleagues, we have decided to add this aortic valve area calculator using the continuity equation.

Continuity equation allows us to determine fairly accurately the area of the aortic valve when studying aortic stenosis with transthoracic echocardiography.

It is a complex formula to use with a manual calculator, so we have decided to facilitate the work to those who need to use it.

Aortic Valve Area

Aortic VTI




LVOT diameter






Click on "Calculate" button"

  • Normal Aortic Valve Area:

  • Normal: higher than 3 cm2.
  • Mild aortic stenosis: between 1.5 cm2 and 2.99 cm2.
  • Moderated aortic stenosis: between 1 cm2 and 1.49 cm2.
  • Severe aortic stenosis: less than 1 cm2.
  • Indexed Aortic Valve Area

  • Mild aortic stenosis: higher than 0.85 cm2.
  • Moderated aortic stenosis: Between 0.6 cm2 and 0.85 cm2.
  • Severe aortic stenosis: Less than 0.6 cm2 [1].

We remind you that this calculator is not 100% reliable. It is only for educational purposes and not for diagnostic purposes. This calculator does not replace the traditional methods for diagnosis and assessment of aortic stenosis.

Data description

  • Aortic valve VTI: velocity time integral of the aortic valve measured with continuous wave oppler. Its value is expressed in centimeters.
  • LVOT VTI: velocity time integral of the left ventricular outflow tract measured with pulsed wave Doppler. Its value is expressed in centimeters
  • LVOT diameter: diameter of the left ventricular outflow tract measured in M-mode. Its value is expressed in millimeters [2].

Continuity Equation for the Calculation of the Aortic Valvular Area

The continuity equation is a physical formula, it states that the rate at which mass enters a system is equal to the rate at which mass leaves the system [3]. The mathematical equation is summarized as follows: A1*V1=A2*V2. Where A is the area, and V is the fluid velocity.

In aortic valve, the same volume of blood passing through the LVOT passes through the aortic valve. So, adjusting the continuity equation, and replacing velocity with VTI, we have the following formula: ALVOT*VTILVOT=AAo*VTIAo. We can calculate the valvular area if we know the LVOT area.

The area of the left ventricular outflow tract is π * (diameterLVOT/2)2, then: AAo=(π * (dLVOT/2)2 * VTILVOT)/VTIAo.

We hope we have helped you with this calculator of the aortic valve area.


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