Stroke Volume and Cardiac Output
A sample calculation is shown below
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.
Cardiac output is = Heart Rate x Stroke Volume
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