Determination of aortic valve area using
the continuity equation .
Top left: Midsystolic parasternal long-axis image from a young man with
mixed aortic stenosis and insufficiency. Left ventricular outflow tract
is indicated(double-headed arrow). LV, left ventricular, D, diameter,
Top right: Left ventricular outflow tract velocity, recorded from the
cardiac apex by pulsed Doppler. The velocity-time integral is determined
by tracing the edge of the velocity-time curve (dots added for emphasis).
LVOT, left ventricular outflow tract.
Bottom right: The jet of high-velocity flow through the stenotic aortic
valve is recorded from the cardiac apex by continuous wave Doppler.
The velocity-time integral is denoted by the dots. AoV, aortic valve.
Bottom left: The continuity equation states that the volume of flow
(stroke volume) through the left ventricular outflow tract is equal
to that through the stenotic aortic valve. Stroke volume is equal to
the product of the cross-sectional area and flow velocity-time integral.
The equation can be solved for the stenotic aortic valve area. SV, stroke
volume; LVOT, left ventricular outflow tract; AoV, aortic valve; CSA,
cross-sectional area; VTI, flow velocity time integral; CSAaov, stenotic
aortic valve area.