How this calculator works
The Gorlin hydraulic equation uses measured catheterization flow, mean pressure gradient and the time available for forward flow. Use systolic ejection time for the aortic valve and diastolic filling time for the mitral valve, in seconds per beat. The conventional constants are 44.3 for aortic and 0.85 × 44.3 for mitral area in cm². Regurgitation, low output and measurement timing can affect results. The result is an estimate for information only and is not medical advice.
Formula
Area(cm²) = CO(mL/min) / [HR(beats/min) × period(s/beat) × K × √mean gradient(mmHg)]. K is 44.3 (aortic) or 0.85 × 44.3 (mitral).
Worked example
Aortic flow 4.43 L/min, rate 100, ejection period 0.2 s and gradient 25 mmHg give 1 cm². Mitral flow 3.7655 L/min with the same rate, filling period and gradient also gives 1 cm².
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Frequently asked questions
Can I enter a peak Doppler gradient?
No. This equation uses a mean invasive transvalvular gradient.
Is the period per minute or per beat?
This page requires seconds per beat and multiplies by beats per minute internally.
Is the Hakki formula the same?
No. Hakki is a simplification that omits explicit rate and flow-period terms under particular assumptions.