# Gorlin Formula Calculator

Determines aortic valve area (AVA) based on cardiac output, heart rate, systolic ejection period and mean gradient.

The Gorlin equation estimates aortic valve area based on the rule that the AVA is equal to the flow through the aortic valve during ventricular systole divided by the systolic pressure gradient across the valve times a constant.

AVA estimations in cm2 can then be analysed to check for potential aortic stenosis and its severity (given that normal AVA is around 3-4 cm2).

### Gorlin Formula

Aortic Valve Area (AVA) = Cardiac Output / (Heart Rate x Systolic Ejection Period x 44.3 x Mean Valvular Gradient)

Where:

• Cardiac output in mL/min;
• Heart rate in beats/min;
• Systolic ejection period in seconds;
• Mean valvular gradient in mmHg;
• Aortic Valve Area in cm2.

Cardiac output
Heart rate
Systolic ejection period
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Steps on how to print your input & results:

2. Then you can click on the Print button to open a PDF in a separate window with the inputs and results. You can further save the PDF or print it.

Please note that once you have closed the PDF you need to click on the Calculate button before you try opening it again, otherwise the input and/or results may not appear in the pdf.

## The Gorlin equation explained

Aortic valve area calculation by the Gorlin formula is an indirect method of determining AVA based on the flow through the valve during ventricular systole divided by the systolic pressure gradient across the valve times a constant (44.3). The below equation relies on the ratio of peak-to-peak instantaneous gradients.

`AVA = Cardiac Output / (Heart Rate x Systolic Ejection Period x 44.3 x √Mean Gradient)`

Where:

• Aortic valve area is expressed in cm2;
• Cardiac Output is considered in mL/min;
• Heart rate is expressed in beats/min;
• Systolic ejection period is considered in seconds;
• Mean valvular gradient is expressed in mmHg.

Normal aortic valve area is around 3 to 4 cm2 and anything less than 1 cm2 is considered severe stenosis.

The ACC/AHA 2006 Guidelines for the Management of Patients With Valvular Heart Disease define the following aortic stenosis severity degrees:

 Aortic Stenosis Severity AVA Mean pressure gradient Peak systolic flow velocity Mild > 1.5 cm2 < 25 mmHg < 3 m/s Moderate 1.0-1.5 cm2 25-40 mmHg 3-4 m/s Severe ≤ 1.0 cm2 > 40 mmHg > 4 m/s

There is also a limitation to the Gorlin formula as in low flow states (for example Cardiac Output of less than 2,500 mL/min) the AVA result tends to overestimate the degree of stenosis. Where the case, the measurement of the true gradient is accomplished by temporarily increasing the cardiac output through infusion of positive inotropic agents.

There are also other indirect AVA measurements based on two other equations, which can be found accessing the Aortic Valve Area Calculator.

## References

### Original reference

Gorlin R, Gorlin SG: Hydraulic formula for calculation of stenotic mitral valve, other cardiac valves, and central circulatory shunts. Am Heart J 41:1-29, 1951.

### Other references

Oh J, Seward JB, Tajik AJ. The Echo Manual 3rd edition. Lippincott, Williams, Wilkins. 2007.

Kern MJ. The Cardiac Catheterization Handbook 4th Edition. Mosby 2003.

Specialty: Cardiology

System: Cardiovascular

Year Of Study: 1951

Article By: Denise Nedea

Published On: June 7, 2020

Last Checked: June 7, 2020

Next Review: June 7, 2025