Aortic Valve Area Calculator

Estimate aortic valve area with the Doppler continuity equation from LVOT diameter, LVOT velocity-time integral, and aortic valve VTI.

Quick Facts

Formula
AVA = (0.7854 x LVOT diameter squared x LVOT VTI) / AV VTI
The Doppler continuity equation. Severe aortic stenosis is generally an area below 1.0 cm2.

Your Results

Calculated
Aortic valve area
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Continuity equation (cm2)
LVOT cross-sectional area
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0.7854 x diameter squared (cm2)
Dimensionless index (DVI)
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LVOT VTI / AV VTI
Severity
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Stenosis grade

Ready

Enter the LVOT diameter, LVOT VTI, and aortic valve VTI, then calculate.

About aortic valve area and the continuity equation

Aortic valve area (AVA) estimates how wide the aortic valve opening is during systole. It is most often derived non-invasively from Doppler echocardiography using the continuity equation, which applies conservation of flow: the stroke volume passing through the left ventricular outflow tract (LVOT) must equal the stroke volume crossing the aortic valve. This calculator returns AVA in square centimeters from three measured values.

The formula

The continuity equation is AVA = (CSALVOT × VTILVOT) / VTIAV, where the LVOT cross-sectional area is 0.7854 × (LVOT diameter)² — the area of a circle, (π/4) × d². VTI is the velocity-time integral, the distance blood travels per beat, measured by Doppler at the LVOT and across the aortic valve. Peak velocities can be substituted for the two VTIs, though VTI is generally preferred.

  • LVOT area: 0.7854 × diameter², so a 2.0 cm LVOT gives about 3.14 cm2.
  • Dimensionless index (DVI): VTILVOT / VTIAV, a ratio that does not depend on the LVOT diameter measurement.

Interpreting the result

Common guideline thresholds grade aortic stenosis by valve area: above 1.5 cm2 is mild, 1.0 to 1.5 cm2 is moderate, and below 1.0 cm2 is severe. A normal aortic valve area is roughly 3 to 4 cm2, and a dimensionless index at or below 0.25 also points to severe stenosis. These cutoffs are read together with the transaortic jet velocity and mean pressure gradient, not in isolation.

When to consult a professional

This tool performs the continuity-equation arithmetic only; it does not diagnose valve disease or account for measurement conditions such as flow state, heart rhythm, or image quality. Any result that concerns you should be reviewed with a licensed cardiologist or your healthcare provider alongside the full echocardiographic study.

Frequently Asked Questions

What is the continuity equation for aortic valve area?
It applies conservation of flow: the stroke volume through the LVOT equals the stroke volume across the aortic valve. So AVA = (LVOT cross-sectional area × LVOT VTI) / aortic valve VTI, where LVOT area = 0.7854 × diameter². The result is the valve opening area in square centimeters.
What aortic valve area indicates severe aortic stenosis?
By common guideline thresholds, an aortic valve area above 1.5 cm2 is mild aortic stenosis, 1.0 to 1.5 cm2 is moderate, and below 1.0 cm2 is severe. A normal aortic valve area is roughly 3 to 4 cm2. These cutoffs are interpreted alongside jet velocity and mean gradient, not alone.
What is the dimensionless index (DVI)?
The dimensionless velocity index is LVOT VTI divided by aortic valve VTI. Because it is a ratio, it avoids the squared error from mismeasuring the LVOT diameter. A DVI of 0.25 or lower suggests severe stenosis, while a normal valve is near 0.75 to 1.0.

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