Severity of aortic stenosis is characterized echocardiographically as Mild: Peak aortic jet velocity 2 to 2.9 m / second or mean gradient < 20 mm Hg Moderate: Peak aortic jet velocity 3 to 4 m / second or mean gradient 20 to 40 mm Hg Severe: Peak aortic jet velocity > 4 m / second or mean gradient > 40 mm Hg Very severe: Peak aortic jet velocity > 5 m / second or mean gradient > 60 mm Hg Clinical judgment and critical review of the data are used to resolve any discordance among these parameters (eg, moderate valve area but severe mean gradient).