Stroke Volume and Cardiac Output 

See below for instructions and an example

Sample Calculation

Cardiac Output.jpg

The LVOT Diameter is measured in the parasternal long axis view in mid systole and is usually around 2cm. 

The LVOT velocity time integral (VTI) provides information regarding blood velocity across the time period of systole and is in the units of cm. It is considered a stroke distance. Typical values are around 15 to 25cm.  One needs to use pulsed wave Doppler in either the apical long axis or 5 chamber view to obtain it. The VTI can be traced out on the ultrasound machine or using digital software offline.

Recall that:

Cardiac output is = Heart Rate x Stroke Volume 

and 

Stroke Volume = LVOT area x LVOT VTI

 

so Stroke Volume= 3.14 (LVOT diameter/2)^2 x LVOT VTI.

In this example:

 

LV stroke volume = 3.14 (2.0cm/2)^2 x 19cm = 60 cm^3 or 60 ml

If the heart rate is 100 then 

Cardiac Output = HR x SV = 100 beats/min x 60 ml/beat = 6000 ml/min or 6.0L/min