Gorlin Formula Calculator
Estimate aortic and mitral valve area from catheterization hemodynamics with the Gorlin equation (Gorlin & Gorlin, 1951) — plus the quick Hakki shortcut, guideline-based stenosis classification, and worked examples.
Aortic valve area — Gorlin equation
Invasive hemodynamic estimate from cardiac catheterization data.
Interpretation aid only. Aortic stenosis severity is graded from valve area together with peak velocity, mean gradient, and clinical context — a single area number never decides severity on its own.
Mitral valve area — Gorlin equation
The original 1951 application: rheumatic mitral stenosis hemodynamics.
Guideline context. The 2020 ACC/AHA Guideline for Valvular Heart Disease stages severe mitral stenosis at MVA ≤ 1.5 cm² (intervention-staging threshold). The echo hemodynamic bands below are the classic mild / moderate / severe grading — so a “moderate” echo result of 1.0–1.5 cm² already meets the guideline’s severe-MS staging criterion.
Hakki formula — quick aortic estimate
Simplified bedside-style shortcut (Hakki et al., 1981). Faster, but less accurate than the full Gorlin equation.
Stenosis classification reference
Hemodynamic grading bands used with valve-area estimates. Sources: EACVI/ASE echo recommendations and the 2020 ACC/AHA Guideline for the Management of Patients With Valvular Heart Disease (Otto et al., Circulation 2021).
| Valve | Mild | Moderate | Severe |
|---|---|---|---|
| Aortic (AVA) | Mild > 1.5 cm² | Moderate 1.0–1.5 cm² | Severe < 1.0 cm² |
| Mitral (MVA) | Mild > 1.5 cm² | Moderate 1.0–1.5 cm² | Severe < 1.0 cm² |
Mitral note: the 2020 ACC/AHA guideline stages severe mitral stenosis at MVA ≤ 1.5 cm² for intervention decisions — stricter than the classic echo “severe < 1.0” band. Aortic bands above align with both echo grading and ACC/AHA severe-AS criteria (AVA ≤ 1.0 cm², typically with mean gradient ≥ 40 mmHg and peak velocity ≥ 4 m/s).
What each variable means
Every input in the Gorlin equation, in plain language.
CO · Cardiac output
Volume of blood the heart pumps per minute (mL/min or L/min), measured by the Fick method or thermodilution during catheterization. Higher flow raises the gradient for the same orifice — the equation is flow-dependent.
HR · Heart rate
Beats per minute at the moment of measurement. Multiplied by the per-beat flow period to get total valve flow time per minute. Must be recorded simultaneously with the gradient.
SEP · Systolic ejection period
Seconds of systolic flow across the aortic valve per beat, read from the aortic pressure tracing. Flow only crosses the aortic valve during this window.
DFP · Diastolic filling period
Seconds of diastolic filling across the mitral valve per beat, from transmitral pressure recordings. The mitral analogue of SEP.
ΔP · Mean gradient
Mean pressure difference across the valve (mmHg), obtained by planimetry of simultaneous pressure curves — not the peak instantaneous or peak-to-peak value (except in the Hakki shortcut).
44.3 / 37.7 · Constants
Empirical hydraulic constants converting flow and gradient into orifice area. 44.3 derives from gravitational acceleration for systolic (aortic) flow; 37.7 is the diastolic (mitral) equivalent (44.3 × 0.85).
Worked catheterization example
A classic teaching case, computed step by step with the Gorlin equation.
Case: suspected severe aortic stenosis
- Hemodynamics: cardiac output 5.0 L/min = 5000 mL/min, heart rate 80 beats/min, systolic ejection period 0.33 s/beat, mean LV–aortic gradient 50 mmHg.
- Total systolic flow time per minute: 0.33 × 80 = 26.4 s/min.
- Denominator: 26.4 × 44.3 × √50 = 26.4 × 44.3 × 7.071 ≈ 8269.8.
- AVA = 5000 ÷ 8269.8 ≈ 0.60 cm² → severe aortic stenosis band (< 1.0 cm²).
Try it above: enter CO 5.0 L/min, HR 80, SEP 0.33, gradient 50 in the Aortic tab — you should get ≈ 0.60 cm². In real practice this patient would still need full echocardiographic assessment and cardiology review; low output can make the Gorlin area read smaller than the true anatomic orifice.
Frequently asked questions
Short answers on the Gorlin equation, the Hakki shortcut, and severity grading.
What is the Gorlin formula?
What is the difference between the Gorlin and Hakki formulas?
What valve area is considered severe aortic stenosis?
Why does the mitral Gorlin formula use 37.7 instead of 44.3?
Can this calculator replace echocardiography or a cardiologist's assessment?
What are SEP and DFP, and how are they measured?
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