SEVERE AORTIC STENOSIS: THE GRADIENT CAN BE MISLEADING
An aortic valve area ≤1.0 cm² suggests severe aortic stenosis (AS), but the mean gradient may be below 40 mmHg.
The gradient depends on blood flow, not just valve narrowing.
1. High-gradient AS
- AVA ≤1.0 cm²
- Mean gradient ≥40 mmHg
- Usually preserved or reduced LVEF
2. Classical low-flow, low-gradient AS
- AVA ≤1.0 cm²
- Mean gradient <40 mmHg
- LVEF <50%
- Stroke volume index ≤35 mL/m²
3. Paradoxical low-flow, low-gradient AS
- AVA ≤1.0 cm²
- Mean gradient <40 mmHg
- LVEF ≥50%
- Stroke volume index ≤35 mL/m²
4. Normal-flow, low-gradient AS
- AVA ≤1.0 cm²
- Mean gradient <40 mmHg
- LVEF ≥50%
- Stroke volume index >35 mL/m²
Why this matters: Low flow can conceal the hemodynamic severity of a stenotic valve. Discordant findings require careful assessment of Doppler measurements, blood pressure, flow state and valve anatomy.
In classical low-flow AS, dobutamine stress echocardiography can help distinguish true severe from pseudo-severe AS. CT aortic valve calcium scoring can help when severity remains uncertain.
Clinical pearl: Never grade AS using the valve area or gradient alone. Integrate AVA, mean gradient, peak velocity, stroke volume, LVEF and clinical context.
Reference: 2025 ESC/EACTS Guidelines for the Management of Valvular Heart Disease.