The Gorlin equation (1951) applies fluid hydraulics to blood flow through a narrowed valve. It is still the reference method in the catheter lab, although it is less accurate at low cardiac output.
How to use the Gorlin Formula Calculator
- Valve
- Cardiac output
- Heart rate
- Systolic ejection or diastolic filling period
- Mean pressure gradient
Results update as you type, and every field accepts the units shown in its menu.
How it works
Choose the valve and enter cardiac output, heart rate, the systolic ejection period (aortic) or diastolic filling period (mitral) per beat and the mean gradient.
Inputs explained
| Field | What to enter |
|---|---|
| Valve | Choose one: Aortic, Mitral |
| Cardiac output | In L/min |
| Heart rate | In bpm |
| Systolic ejection or diastolic filling period | In s per beat |
| Mean pressure gradient | In mmHg |
What each result means
- Valve area (Gorlin) = [Cardiac output]×1000÷([Heart rate]×[Systolic ejection or diastolic filling period]×[Valve]×sqrt([Mean pressure gradient]))
- Valve area (Hakki) = [Cardiac output]÷sqrt([Mean pressure gradient])
Example values
How the main result changes when Cardiac output changes and everything else stays at the example values above:
| Cardiac output (L/min) | Valve area (Gorlin) (cm²) |
|---|---|
| 2.5 | 0.34 |
| 3.75 | 0.51 |
| 5 | 0.68 |
| 6.25 | 0.85 |
| 7.5 | 1.02 |
| 10 | 1.36 |
Health note: this calculator is for education and screening only and is not a diagnosis or treatment advice. Discuss your results with a qualified clinician.
Formula
Valve area (cm²) = CO (mL/min) ÷ (HR × ejection or filling period (s) × C × √mean gradient)
C = 44.3 for the aortic valve, 37.7 for the mitral valve
Hakki: area ≈ CO (L/min) ÷ √mean gradient
Worked example
Inputs — Valve: Aortic; Cardiac output: 5 L/min; Heart rate: 75 bpm; Systolic ejection or diastolic filling period: 0.33 s per beat; Mean pressure gradient: 45 mmHg.
Results — Valve area (Gorlin) = 0.68 cm²; Valve area (Hakki) = 0.75 cm².
Key terms
- SEP
- Systolic ejection period.
- DFP
- Diastolic filling period.
Frequently asked questions
What is the Gorlin constant?
44.3 for the aortic valve and 37.7 (44.3 × 0.85) for the mitral valve.
Why might Gorlin be inaccurate?
At low cardiac output it underestimates valve area.
What is the Hakki formula?
A simplified version: cardiac output divided by the square root of the gradient.