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

AS - Continuity Eq

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

LVOT Diameter (d):

 cm

LVOT VTI
(by pulsed Doppler):

 cm

Aortic valve VTI
(by continuous Doppler):

 cm


 		  

Answers

LVOT Area:

 cm2

Aortic Valve Area (AVA):

 cm2

Formulas

LVOT Area = (1/2 * d)2 * pi

AVA = LVOT Area * (LVOT VTI / AV VTI)

Reference
Skjaerpe T, Hegrenaes L, Hatle L. Non-invasive estimation of valve area in patients with aortic stenosis by Doppler ultrasound and two dimensional echocardiography. Circulation 1985;72:810-8.

Note: Interestingly, the authors called the method 'equation of continuity' rather than 'continuity equation'.