ECHONOMY
Tools for Echocardiographic Calculations
Muhamed Saric, MD, PhD
New York University


Purpose

To
calculate aortic valve area using the continuity principle which states that
the stroke volume that passes through the LVOT in systole is equal to the
stroke volume passing through the aortic valve. 
Technical Hints

Interrogate the Doppler flow
through the aortic valve from any available echocardiographic window and use
the highest Doppler values obtained. 
Calculator

Body Surface
Area 


Body Surface Area 

m^{2} 



LVOT Data 


LVOT Vmax
(by pulsed Doppler) 

m/sec 
LVOT VTI
(by pulsed Doppler) 

cm 
LVOT Diameter (d) 

cm 



LVOT Area: 

cm^{2} 
LVOT Stroke Volume (SV) 

mL 
LVOT Stroke Volume Index (SVI) 

mL/m^{2} 



Aortic Valve
Data 


AV Vmax
(by continuous Doppler) 

m/sec 
AV VTI
(by continuous Doppler) 

cm 



AV Peak Gradient 

mm Hg 
**AV Mean Gradient 

^{ }mm
Hg 
AV Area (AVA) 

cm^{2} 
AV Area Index (AVAI) 

cm^{2}/m^{2} 
Dimensionless Index 





Formulas
LVOT Area = (1/2 * d)^{2}
* pi
SV = LVOT Area * LVOT VTI
AV Peak Gradient  4 * (AV Vmax)^{2}
** AV Mean Gradient should be measured directly. Here a rough approximation
is given as AV Mean Gradient = 2/3 * AV Peak Gradient
AVA = LVOT Area * (LVOT VTI / AV VTI)
Dimensionless Index = LVOT Vmax / AV Vmax 
Reference

Skjaerpe T, Hegrenaes L, Hatle L.
Noninvasive estimation of valve area in patients with aortic stenosis by
Doppler ultrasound and two dimensional echocardiography.
Circulation
1985;72:8108.
Note: Interestingly, the authors called the method 'equation of
continuity' rather than 'continuity equation'. 