Aortic stenosis
Valve area by the continuity equation, peak and mean gradients, and a check for low-flow, low-gradient AS when the numbers disagree.
ASE/EACVI 2017 recommendations on aortic stenosis
How it's calculated
Continuity equation
LVOT area = π × (diameter ÷ 2)², diameter in cm (mm ÷ 10) Stroke volume = LVOT area × LVOT VTI AVA = stroke volume ÷ AV VTI Dimensionless index = LVOT VTI ÷ AV VTI Peak gradient = 4 × Vmax²| Sclerosis | Mild | Moderate | Severe | |
|---|---|---|---|---|
| Peak velocity (m/s) | ≤ 2.5 | 2.6–2.9 | 3.0–3.9 | ≥ 4.0 |
| Mean gradient (mmHg) | – | < 20 | 20–39 | ≥ 40 |
| AVA (cm²) | – | > 1.5 | 1.0–1.5 | < 1.0 |
| AVA index (cm²/m²) | – | > 0.85 | 0.60–0.85 | < 0.6 |
| Dimensionless index | – | > 0.50 | 0.25–0.50 | < 0.25 |
Discordant grading
When AVA is under 1.0 cm² but the mean gradient is under 40 mmHg, flow decides the next step. Stroke volume index under 35 mL/m² means low flow: with LVEF under 50% this is classical low-flow, low-gradient AS (dobutamine stress echo); with preserved LVEF it is paradoxical low-flow AS (CT calcium score helps). With normal flow, the AS is usually moderate and the LVOT diameter deserves a second look.
BSA by Mosteller. Baumgartner H, et al. J Am Soc Echocardiogr 2017;30:372–392.
For education and as a reporting aid. A result supports the reading of the full study and does not replace it.