Thread by @Pocus101

Does Measuring Cardiac Output ❤️ with #POCUS seem confusing 😕? Let's Demystify that today 😀!

1⃣Measure LVOT Diameter
2⃣Measure LVOT VTI
3⃣Measure HR
4⃣Calculate SV and CO
5⃣FREE Pocket Guide PDF!

✅New Blog Post & PDF
🔗👉pocus101.com/CardiacOutput

#medtweetorial 👇(1/n)

Here is the link to the FREE Downloadable Cardiac Output PDF

🔗👉pocus101.com/CardiacOutput

Cardiac output (CO) is the total volume of blood moved by the heart per minute. It is a product of the left ventricular stroke volume (SV) and the heart rate (HR).

Cardiac output (mL/min) = Stroke Volume (mL/cycle) x Heart Rate (bpm)

🔗👉pocus101.com/CardiacOutput

Just think of stroke volume as a cylindrical volume coming out of the LV during each contraction of the heart.

This is the basis for how the ultrasound machine will calculate SV and CO.

🔗👉pocus101.com/CardiacOutput

You need TWO measurements to calculate SV

1⃣First is the LVOT Diameter

2⃣Second is the distance that one blood cell travels during one heartbeat (calculated using the velocity-time integral or VTI).

Then simply use the formula for Cylinder volume!

🔗👉pocus101.com/CardiacOutput

Let's go over EXACTLY how to measure cardiac output Step-by-Step below!

STEP 1: Get the Parasternal Long Axis View

Ensure you can clearly visualize your left ventricular outflow tract (LVOT) and the aortic valve. Look to ensure you can see your aortic valve opening and closing.

🔗👉pocus101.com/CardiacOutput

STEP 2: Measure LVOT Diameter

Freeze your screen when you have the best view of your aortic valve at mid-systole (when the valves are wide open).

Then Measure the LVOT Diameter, typically this measurement is around 2 cm. (Using Zoom function helps)

🔗👉pocus101.com/CardiacOutput

STEP 3: Get the Apical 5-Chamber View

Next, obtain an Apical 5-Chamber View. Again, you will need to visualize the LVOT and aortic valve.

🔗👉pocus101.com/CardiacOutput

STEP 4: Place PW Doppler Gate at LVOT

Make sure to align the pulse wave Doppler gate and LVOT as parallel as possible in order to get the best VTI tracing. The more your angle is off the more you will underestimate the cardiac output.

🔗👉pocus101.com/CardiacOutput

STEP 5: Trace LVOT VTI

Trace the outline of one of the systolic waveforms (yellow outline).

The LVOT VTI will output as a distance in cm and represents the distance that blood travels in one heartbeat.

🔗👉pocus101.com/CardiacOutput

Here is a video we made going over exactly how to get the LVOT VTI

STEP 6: Measure Heart Rate

Place the cursor from one peak of a wave to another peak and the machine should automatically calculate the heart rate for you (the example below shows a heart rate of 75 bpm).

You can also just use HR from the pt monitor

🔗👉pocus101.com/CardiacOutput

STEP 7: Calculate Cardiac Output

Now after you have completed the 3 measurements (LVOT diameter, LVOT VTI, and HR) the machine should automatically calculate the cardiac output for you.

For example below, the cardiac output is 2.46 L/min

🔗👉pocus101.com/CardiacOutput

Of course, it's always good to be able to know how to calculate the cardiac output yourself in case the ultrasound is having any issues.

🔗👉pocus101.com/CardiacOutput

Make sure to download the Cardiac Output Pocket Guide!

🔗👉pocus101.com/CardiacOutput