Gorlin Formula Calculator

Calculate aortic or mitral valve area from cardiac catheterization measurements using the standard Gorlin formula.

Quick Facts

Formula
Area = Flow / (44.3 x K x sq.root of mean gradient)
Flow = cardiac output divided by (flow period x heart rate).
Empiric constant K
1.0 aortic, 0.85 mitral
Corrects for orifice geometry and flow turbulence.
Normal valve area
Aortic ~3-4 cm2, mitral ~4-6 cm2
Reference range only, not a diagnostic cutoff by itself.

Your Results

Calculated
Valve area
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Gorlin formula result (cm²)
Flow rate
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During valve opening period
Flow time per minute
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Valve open time (sec/min)
Severity
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Common clinical threshold

Ready

Enter catheterization data, then calculate the valve area.

About the Gorlin Formula

The Gorlin formula was published by Richard Gorlin and Sidney Gorlin in 1951 to calculate the cross-sectional area of a stenotic heart valve from cardiac catheterization measurements. It remains the reference method behind valve area estimates reported in the cath lab, and it underlies the simplified valve-area equations used in echocardiography as well. The formula converts blood flow and the pressure drop across a valve into an area in square centimeters, based on the physics of flow through a fixed orifice (Torricelli's law).

How the formula works

The valve area equals the flow rate through the valve during its opening period, divided by an empiric constant, 44.3, times a valve-specific correction factor K, times the square root of the mean pressure gradient across the valve:

  • Flow rate is the cardiac output (converted to mL/min) divided by the total time per minute the valve is open — the systolic ejection period for the aortic valve, or the diastolic filling period for the mitral valve, each multiplied by the heart rate.
  • The constant K is 1.0 for the aortic valve and 0.85 for the mitral valve. It was added after the original derivation to correct for orifice geometry and flow turbulence that the pure physics term does not capture.
  • The mean pressure gradient is the average pressure difference across the valve during its flow period, typically measured directly during catheterization or estimated from Doppler echocardiography.

Interpreting valve area

Smaller calculated areas indicate more severe stenosis. Common reference bands used in practice are: severe stenosis below 1.0 cm², moderate stenosis from 1.0 to 1.5 cm², and mild stenosis above 1.5 cm², with a normal aortic valve area of roughly 3 to 4 cm² and a normal mitral valve area of roughly 4 to 6 cm². These bands are general clinical reference points, not a substitute for a full evaluation.

When to consult a professional

This tool performs the standard Gorlin formula arithmetic for education and record review. It is not a diagnosis and does not direct treatment. Valve area estimates should always be reviewed by a cardiologist alongside symptoms, imaging, and the rest of the hemodynamic picture before any clinical decision is made.

Frequently Asked Questions

What is the Gorlin formula used for?
The Gorlin formula is used in cardiac catheterization to calculate the cross-sectional area of a stenotic heart valve (aortic or mitral) from measured cardiac output, heart rate, the valve's flow period, and the mean pressure gradient across it. It converts hemodynamic measurements into a valve area in square centimeters, which is used to grade the severity of valve stenosis.
What is the difference between the aortic and mitral versions of the formula?
Both versions use the same underlying equation. The aortic formula uses the systolic ejection period, the time the aortic valve is open during systole, with an empiric constant of 1.0. The mitral formula uses the diastolic filling period, the time the mitral valve is open during diastole, with an empiric constant of 0.85. The constant corrects for turbulence and orifice geometry that the original derivation from Torricelli's law does not capture exactly.
What valve area indicates severe stenosis?
Using common clinical thresholds, a calculated area below 1.0 square centimeter indicates severe stenosis for either valve, 1.0 to 1.5 square centimeters indicates moderate stenosis, and above 1.5 square centimeters indicates mild stenosis. Normal valve area is roughly 3 to 4 square centimeters for the aortic valve and 4 to 6 square centimeters for the mitral valve. These are general reference bands; a cardiologist interprets the number alongside symptoms, imaging, and other hemodynamic data.

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