Calculate effective orifice area or aortic valve area with the Gorlin formula from cardiac output, heart rate, ejection period and mean gradient.

Time the aortic valve ejects during one beat, not total seconds per minute.

Use the mean transvalvular gradient, not a peak instantaneous gradient.

Optional settings

Medical disclaimer: For informational use onlyโ€”not medical advice and not a diagnosis. Valve stenosis severity requires clinician interpretation using multiple measurements (e.g., symptoms, gradients/velocities, flow state, and imaging quality). If you have chest pain, fainting, severe shortness of breath, or stroke symptoms, seek emergency care.

Related Calculators

Estimated Aortic Valve Area (Gorlin) Formula

The conventional Gorlin formula below estimates aortic valve area using catheterization-style measurements. It is not the Doppler continuity-equation effective orifice area, and the methods are not interchangeable.

EOA (cmยฒ) = CO (mL / min) รท [HR (beats / min) ร— SEP (s) ร— 44.3 ร— โˆš(mean gradient (mmHg))]

Variables:

  • EOA in this displayed Gorlin-style formula denotes estimated aortic valve area in cmยฒ
  • CO is the cardiac output in milliliters per minute (mL/min) (1 L/min = 1000 mL/min)
  • HR is the heart rate in beats per minute (beats/min)
  • SEP is the systolic ejection period in seconds per beat (s/beat), not total seconds per minute
  • MG is the mean transvalvular pressure gradient in millimeters of mercury (mmHg)

References / further reading

The ASE/EACVI aortic stenosis recommendations distinguish Doppler effective orifice area from Gorlin-derived valve area. Comparative validation research also describes differences between measurement methods. This calculator does not assign stenosis grades.

To calculate the effective orifice area, divide the cardiac output (in mL/min) by 44.3 times the product of the heart rate, systolic ejection period, and the square root of the mean gradient (in mmHg).

What is an Effective Orifice Area?

The effective orifice area (EOA) is a measure used in cardiology to quantify the size of the opening through which blood flows in the heart, particularly through heart valves. It is an important parameter for assessing the severity of valve stenosis, which is a condition where the valve opening is narrowed, restricting blood flow. In practice, valve area/EOA can be estimated using different methods such as the Gorlin equation (cardiac catheterization/hemodynamics) or the continuity equation (echocardiography). Area must be interpreted with flow state, gradients, pressure recovery, regurgitation and measurement quality; a single area estimate cannot diagnose severity or determine treatment.

How to Calculate Effective Orifice Area?

The following steps outline how to calculate the Effective Orifice Area.

  1. First, determine the cardiac output (CO) (often reported in L/min; convert to mL/min by multiplying by 1000 if needed).
  2. Next, determine the heart rate (HR) in beats per minute.
  3. Next, determine the systolic ejection period (SEP) in seconds.
  4. Next, determine the mean gradient (MG) in millimeters of mercury (mmHg).
  5. Finally, calculate the Effective Orifice Area using the formula EOA = CO(mL/min) / [44.3 ร— HR ร— SEP ร— โˆšMG].
  6. Select the cardiac Gorlin mode above. Ejection time must be positive and shorter than the cardiac cycle (60/HR seconds per beat). This consistency check is not a clinical diagnostic threshold.

Example Problem : 

Use the following variables as an example problem to test your knowledge.

Cardiac Output (CO) = 5 L/min (5000 mL/min)

Heart Rate (HR) = 70 beats/min

Systolic Ejection Period (SEP) = 0.3 sec

Mean Gradient (MG) = 10 mmHg. The Gorlin estimate is 5000 / [70 ร— 0.3 ร— 44.3 ร— โˆš10] โ‰ˆ 1.6996 cmยฒ. This example is educational and does not establish a diagnosis.