Aortic Valve Area (AVA): Continuity equation-derived functional valve orifice area; severe aortic stenosis = AVA <1.0 cm².
Aortic valve area (AVA) is the calculated functional orifice area of the aortic valve, derived by the Doppler continuity equation: AVA = (LVOT area × LVOT VTI) / AV VTI. It is the primary quantitative metric for grading aortic stenosis severity. Severe AS is defined as AVA <1.0 cm² (or <0.6 cm²/m² indexed to BSA). The continuity equation is the most reproducible and guidelines-endorsed measure of AS severity.