A valve area under 1.0 cm² with a mean gradient under 40 mmHg is a common echo report, and it is not a measurement to average away. First check for measurement error, especially an underestimated outflow tract diameter. Then calculate the stroke volume index: under 35 mL/m² means low flow, and the stenosis may be severe despite the modest gradient.
With reduced ejection fraction, low-dose dobutamine echo helps separate true from pseudo-severe stenosis. With preserved ejection fraction, calcium scoring on non-contrast CT helps, using sex-specific thresholds.
- Recheck the outflow tract diameter before accepting a discordant result.
- Calculate the stroke volume index; under 35 mL/m² means low flow.
- Use dobutamine echo when ejection fraction is reduced.
- Use aortic valve calcium scoring when ejection fraction is preserved.
Why it matters
Low-flow severe stenosis is the form most often mislabelled as moderate and left to progress.
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