Aortic Valve Area Calculator

Aortic Valve Area Calculator. Calculate Aortic Valve Area (AVA) using three established methods: the Continuity Equation, the Gorlin Equation, and the Hakki Equation. Enter your echocardiographic measurements — LVOT diameter, LVOT VTI, AV VTI, and BSA — along with hemodynamic values like cardiac output, heart rate, systolic ejection period, and mean/peak-to-peak gradient. You get back AVA in cm², indexed AVA, VTI ratio, and stenosis severity classification. Also try the Estimated Arterial Age — Arterial Age.

LVOT Diameter *

Left ventricular outflow tract diameter measured by echocardiography

LVOT VTI *

Velocity-time integral of the LVOT measured by pulsed-wave Doppler

Aortic Valve VTI *

Velocity-time integral across the aortic valve measured by continuous-wave Doppler

Body Surface Area (BSA)

m²

Used to calculate indexed AVA. Leave blank to skip indexing.

Cardiac Output *

mL/min

Cardiac output in mL/min for the Gorlin equation

Heart Rate *

bpm

Heart rate in beats per minute

Systolic Ejection Period *

sec

Duration of systolic ejection per beat in seconds

Mean Valvular Gradient *

mmHg

Mean transvalvular pressure gradient in mmHg (used in Gorlin equation)

Cardiac Output (Hakki) *

L/min

Cardiac output in L/min for the simplified Hakki equation

Peak-to-Peak Gradient *

mmHg

Peak-to-peak transvalvular pressure gradient in mmHg (used in Hakki equation)

Results

AVA (Continuity Equation)

VTI Ratio (Dimensionless Index)

Indexed AVA

AVA (Gorlin Equation)

AVA (Hakki Equation)

Stenosis Severity (Continuity)

Results Table

What is the normal aortic valve area?

The normal aortic valve area is 3–4 cm². Symptoms of aortic stenosis typically do not appear until the AVA falls below 1 cm² (severe stenosis). Mild stenosis is generally defined as AVA > 1.5 cm², and moderate as 1.0–1.5 cm². See also our use the HAS-BLED Score Calculator.

What is the continuity equation for AVA?

The continuity equation states that blood flow through the LVOT must equal flow through the aortic valve. The formula is: AVA = (LVOT diameter² × 0.7854 × LVOT VTI) / AV VTI. It relies on the principle of conservation of mass and is the most widely used echocardiographic method.

How does the Gorlin equation differ from the continuity equation?

The Gorlin equation estimates AVA using invasive hemodynamic data: AVA = Cardiac Output / (Heart Rate × Systolic Ejection Period × 44.3 × √Mean Gradient). It was developed from cardiac catheterization measurements and uses the hydraulic orifice formula, whereas the continuity equation relies on Doppler echocardiographic data.

What is the Hakki equation and when is it used?

The Hakki equation is a simplified version of the Gorlin formula: AVA = Cardiac Output (L/min) / √Peak-to-Peak Gradient (mmHg). It provides a quick bedside estimate and is most accurate at normal heart rates (around 70–80 bpm). It may overestimate AVA at faster heart rates.

What is the VTI ratio (dimensionless index)?

The VTI ratio is calculated as LVOT VTI divided by AV VTI. A ratio below 0.25 generally indicates severe aortic stenosis. It is useful when the LVOT diameter measurement is uncertain, as it does not depend on that measurement.

What is indexed AVA and why does it matter?

Indexed AVA is the AVA divided by the patient's body surface area (BSA), expressed in cm²/m². It accounts for differences in body size — an AVA of 1.0 cm² may be severe in a small patient but moderate in a larger one. Severe AS is typically defined as indexed AVA < 0.6 cm²/m².

What are the echocardiographic criteria for severe aortic stenosis?

Severe aortic stenosis is generally defined by AVA < 1.0 cm², indexed AVA < 0.6 cm²/m², mean gradient > 40 mmHg (or > 50 mmHg by some criteria), peak aortic velocity > 4.0 m/s, and VTI ratio < 0.25. All parameters should be interpreted together in clinical context.

Why might different equations give different AVA values?

Each equation uses different inputs and assumptions. The continuity equation uses Doppler-derived velocities, the Gorlin equation uses catheterization hemodynamics, and the Hakki equation is a simplified approximation. Discrepancies can arise from measurement variability, heart rate differences, or low-flow states. Clinical correlation is always recommended. You might also find our MCA Calculator (Middle Cerebral Artery) useful.