Aortic Valve Area (Continuity Equation using VMax)
Definition of Aortic Stenosis Severity
AVA (cm2)
AVAI (cm2/m2)
Normal
3.0-4.0
Mild
>1.5
>0.85
Moderate
1.0-1.5
0.60-0.85
Severe
<1.0
<0.6
Aortic Valve Area (VMax)
Aortic valve area can be calculated by using the principle of conservation of mass — "What comes in must go out". Although VTI is a more accurate method, using maximum velocities is simpler and can generate a very close result. The simplified continuity equation is based on the concept that in native aortic valve stenosis the shape of the velocity curve in the outflow tract and aorta is similar so that the ratio of LVOT to aortic jet VTI is nearly identical to the ratio of the LVOT to aortic jet maximum velocity (V).
Aortic valve area indexed to body surface area should be considered for the large and small extremes of body surface area.
For patients with prosthetic aortic valves, patient-prosthesis mismatch is suspected when effective orifice area (EOA) indexed to body surface area <0.85 to 0.9 cm2/m2. Patient-prosthesis mismatch is considered severe when EOA index <0.65.
EOA Index (cm2/m2)
Moderate
<0.85
Severe
<0.65
AVA =
π*(LVOT/2)2*V1
V2
Variable
Definition
V1
Subvalvular velocity (m/s)
V2
Maximum velocity across the valve (m/s)
LVOT
Left ventricular outflow tract diameter (cm)
Weight
Weight (kg or lb)
Height
Height (cm or in)
AVA
Aortic Valve Area (cm2)
AVA Index
Aortic Valve Area indexed to BSA (cm2/m2)
References
Baumgartner H, et al. Echocardiographic assessment of valve stenosis: EAE/ASE recommendations for clinical practice. J Am Soc Echocardiogr. 2009 Jan;22(1):8,10.
Zoghbi WA, et al. Accurate noninvasive quantification of stenotic aortic valve area by Doppler echocardiography. Circulation 1986; 73:452-459.
Grayburn PA, et al. Pivotal role of aortic valve area calculation by the continuity equation for Doppler assessment of aortic stenosis in patients with combined aortic stenosis and regurgitation. Am J. Cardiol 1988; 61:376-381.
Carabello BA, et al. ACC/AHA 2006 guidelines for the management of patients with valvular heart disease. Circulation 2006; 114(5):e84-231.
Pibarot P, Dumesnil JG. Hemodynamic and clinical impact of prosthesis-patient mismatch in the aortic valve position and its prevention. J Am Coll Cardiol 2000;36:1131-41.
Jamieson E. et al. Surgical Management of Valvular Heart Disease 2004. Canadian Cadiovascular Society Consensus Conference. Can J Cardio Vol 2004; 20 Suppl E:18E-19E.
Developer: Edward Brawer