Aortic Valve Area (Continuity) Calculator

Health

The Aortic Valve Area Calculator estimates aortic valve area (AVA) from echocardiographic measurements using the continuity equation. It compares flow through the LVOT with flow through the aortic valve. The formula used is: AVA = (LVOT area × LVOT VTI) ÷ AV VTI, where LVOT area = π × (LVOT diameter ÷ 2)².

Rates and fees change frequently. Always confirm the current figures with the official authority before relying on this result.

Formula

AVA = (LVOT area × LVOT VTI) ÷ AV VTI; LVOT area = π × (LVOT diameter ÷ 2)²
  • The Aortic Valve Area Calculator updates instantly when you change any measurement.
  • Formula: AVA = (LVOT area × LVOT VTI) ÷ AV VTI, with LVOT area = π × (LVOT diameter ÷ 2)²
  • Input definitions: • LVOT Diameter: left ventricular outflow tract diameter measured in the parasternal long-axis view (cm) • LVOT VTI: velocity-time integral of LVOT flow from pulsed-wave Doppler (cm) • Aortic Valve VTI: velocity-time integral across the aortic valve from continuous-wave Doppler (cm)
  • The continuity equation assumes flow is conserved between the LVOT and the aortic valve.
  • Severity bands are a general guide: >1.5 cm² no significant stenosis, 1.0–1.5 mild, 0.75–1.0 moderate, <0.75 severe.
  • LVOT diameter is squared, so small measurement errors there have a large effect on the result.

Example Calculation

Inputs
  • LVOT Diameter (cm): 2
  • LVOT VTI (cm): 22
  • Aortic Valve VTI (cm): 90

With an LVOT diameter of 2.0 cm, LVOT area = π × 1.0² = 3.14 cm². Then AVA = (3.14 × 22) ÷ 90 = 0.77 cm², which falls in the moderate stenosis range.

Frequently asked questions

What is the continuity equation?
It is based on conservation of flow: the volume passing through the LVOT equals the volume crossing the aortic valve, so AVA = (LVOT area × LVOT VTI) ÷ AV VTI.
Why square the LVOT diameter?
LVOT area is a circle, π × radius². Because the diameter is squared, a small error in measuring it causes a proportionally larger error in the calculated valve area.
How is aortic stenosis graded by area?
As a general guide, above 1.5 cm² is not significant, 1.0–1.5 cm² is mild, 0.75–1.0 cm² is moderate, and below 0.75 cm² is severe.
What units should I enter?
Enter the LVOT diameter and both VTI values in centimetres, as reported on the echocardiogram.
Is this a diagnosis?
No. This is a screening estimate that supports interpretation of echo data. Diagnosis and management must be made by a qualified clinician.