Calculating Cardiac Output

Items needed

To calculate Cardiac Output from an echo report, you will need to find the following items on the echo report:

LVOT diameter - this is the diameter of the LV outflow track.
LVOT VTI - velocity time integral, meaning how far blood is traveling over a certain time.
Heart Rate - this is usually found at the top of the report.

For a full hemodynamic profile, you will also need:

MAP - mean arterial pressure
RAP or CVP

Calculators

These will definitely save you some time.

1

Calculate Stroke volume

You are essentially using the above data points to calculate the volume of a cylinder: Volume = π x radius² x height. In echo terms it looks like: Stroke volume = π x (LVOT diameter / 2)² x LVOT VTI.

2

Calculate Cardiac Output

Cardiac output = Stroke volume (from first step) x heart rate.

3

Calculate SVR

You will need the following info:

Mean arterial pressure (MAP). You may need to calculate MAP from the BP at the top of the echo report.
Right atrial pressure (RAP) or CVP. RAP can sometimes be found on the echo reports.

MAP = 1/3 (SBP – DBP) + DBP.

Then calculate SVR = [(MAP - CVP) / CO] x 80.

Example Problem

Step 1

Stroke volume = π x (LVOT diameter / 2)² x LVOT VTI.

Stroke volume = π x (2cm/2)² x 21.8cm

Stroke volume = 68.45 ml

Step 2

Cardiac Output = Stroke volume x heart rate.

Cardiac Output = 68.45ml x 86 bpm

Cardiac Output = 5.8 lpm

Step 3

MAP = 1/3 (SBP – DBP) + DBP.

MAP = 1/3 (127 - 56) + 56

MAP = 79.6

SVR = [(MAP - CVP) / CO] x 80.

SVR = [(79.6 - 3) / 5.8 ] x 80

SVR = 1056.6 dynes-sec-cm^-5