How To Calculate Stroke Volume In Echocardiography (The EASY Way)
How To Calculate Stroke Volume With Echocardiography
If you’re just starting out learning about echocardiography, then you’re in luck. That’s because the echo machines of today perform every possible calculation that you can imagine for you!
If you’ve been doing echocardiograms for a while, then you probably remember to good old days of having to calculate everything by hand.
The same was true for calculating left ventricular stroke volume. But thankfully, now days stroke volume is automatically calculated by the echo machine. Often times, depending on your machines settings, left ventricular stroke volume is given to you even when you’re not necessarily looking for it, simply based off all the other measurements you’ve taken during your routine protocol.
But in case you’re wanting to know how to calculate LV stroke volume with echocardiography, here’s a few very simple steps you can take to get a very accurate stroke volume measurement.
1. Determine Cross Sectional Area
First you need to calculate the cross sectional area of the left ventricular outflow tract, or LVOT. You’ll figure this from the parasternal long axis (PLAX) view. To get the cross sectional area of the LVOT, you first measure the LVOT diameter during systole. You’ll take this measurement at the insertion points of the right coronary cusp of the aortic valve and the non-coronary cusp of the aortic valve.
Pro Tip: I always like to zoom in on the valves to measure the LVOT cross sectional area. I believe you can get a much more accurate measurement by doing this one simple thing.
2. Determine Left Ventricular Outflow Tract VTI (LVOT VTI)
Next, you need to obtain the left ventricular outflow tract VTI, or LVOT VTI. The best place to measure the LVOT VTI with echocardiography is from the apical 5 chamber view.
Place the pulsed wave Doppler sample, or PW Doppler, in the LVOT near the aortic valve leaflets. But be sure to stay in the LVOT and do not measure the blood flow past the aortic valve.
Pro Tip: When obtaining the LVOT VTI, I always strive to also obtain at least one aortic valve click on my spectral Doppler tracing. This lets me know that my PW sample volume is inside the left ventricular outflow tract, but close to the aortic valve…right where we want to be.
Calculation For Stroke Volume In Echocardiography
If you’ve carefully obtained the above measurements, and have a reasonably modern echo machine, then you should have everything you need to obtain the left ventricular stroke volume.
However, if you need to calculate stroke volume manually, then here is how you can figure it out on your own.
Stroke Volume Calculation
Stroke Volume = .785 x LVOT diameter2 x LVOT VTI
What Is Stroke Volume?
Stroke volume is the amount of blood pumped by the left ventricle of the heart in one contraction, or with each beat. As you probably already know, only about two-thirds of the blood in the left ventricle is pumped out with each beat. Normal stroke volume in a healthy adult can be anywhere between 60ml and 100ml.
Stroke Volume Units
Stroke volume is measured in ml’s, or milliliters. You may also find that stroke volume is measured in cc’s. Keep in mind that cc’s and milliliters are the same unit of measurement and can be used interchangeably.
As you can see, calculating left ventricular stroke volume in echocardiography is really very simple. And like I mentioned, if you’re following a basic ICAEL protocol, like this one, then you’re already most likely getting all the information you need to calculate the stroke volume.
If your echo machine isn’t already calculating it for you, it’s probably a very simple fix. All you need to do is change a setting on the machine. If you’re uncomfortable doing that yourself, call your vendor or rep, and they should be more than happy to walk you through the process.