IVC Assessment With Echo: What Does IVC Collapse Even Mean?
Taking the time to assess the IVC (inferior vena cava) in our routine echocardiogram studies can yield a lot of information. By taking just a few minutes to view the IVC and assess IVC collapsibility, we can easily determine the patient’s intravascular volume status as well as an estimation of the patient’s central venous pressure (CVP).
If you’ve spent anytime around a cardiac sonographer, then for sure you’ve heard them talk about IVC collapse. Did the Inferior Vena Cava collapse? Was it dilated and collapse? Was it normal in diameter and collapse?
So what exactly does all of this talk about collapse mean? Keep reading, and we’ll explain in very simple terms.
What Is The IVC?
The way I like to explain what the IVC is to my patients is that it’s a large vein that brings the blood from the middle and lower half of your body back to your heart.
More specifically, it carries the deoxygenated blood from the lower half of your body back to the right atrium of the heart. Our bodies have two vena cava, a superior (upper) and an inferior (lower) vena cava. Both of these large veins attach to the right atrium.
Why It’s Important To Assess The IVC with Echo
There are several very important reasons to assess the IVC with echocardiography. A couple of the more important are to determine right atrial pressure or central venous pressure, determining the pulmonary artery pressure as well as assessing fluid levels in the patient. By obtaining these few measurement, physicians are able to treat patients on the spot.
How To Measure Right Atrial Pressure With The IVC
We know that the inferior vena cava is attached to the right atrium. So if we can estimate what the pressure is in the section of IVC that is in close proximity to that right atrium, then we can assume that the pressure in the right atrium is the same or similar. (This is true because there is no valve between the right atrium and the IVC).
In the subcostal view, rotate the ultrasound probe counterclockwise to obtain a long axis image of the vein.
In patients who have a normal right atrial pressure, you will see that the IVC is not dilated and collapses when the patient takes a breath in.
However, in many of the echo patients that we see, we know that the right atrial pressure is elevated. How do we know this?
These quick reference cards for cardiac sonographers and cardiogists include right atrial pressure estimation, and is a great way to always help you remember what right atrial pressure might be.
What The IVC Looks Like With Elevated Right Atrial Pressure
Essentially, what we do is simply measure the IVC diameter to determine if it’s dilated. If its dilated, then we know the patients RAP is elevated. But by how much? To get an even better idea of the right atrial pressure, we can ask the patient to inhale, or sniff in through their nose.
What Does IVC Collapse Mean?
By doing this “sniff test”, we can look at the inferior vena cava and see if it collapses or not. If it doesn’t collapse, or decrease in diameter of at least 50%, then we know the right atrial pressure is even higher. By asking the patient to sniff, it generates a sudden decrease in intrathoracic pressure, which would normally cause the IVC to collapse at least 50%.
How To Measure The IVC With 2D Echo
From the subcostal window, you want to image the IVC in long axis. Optimize the ultrasound image and zoom in if you need to.
With your calipers, you want to try to measure its diameter approximately 2 cm from its attachment point to the right atrium. Many cardiac sonographers that I know say that this 2 cm mark is just distal to where the hepatic vein attaches to the IVC.
If you are using M mode, then it is at this spot that you want to place your cursor. Regardless of whether you are using 2D measurements or M mode, make sure you are measuring it when it is at it’s widest diameter.
IVC Collapsibility Index And Normal IVC Pressure
Below is a chart showing the IVC collapsibility index. As you can see, and as I mentioned earlier, depending on the diameter of the IVC in combination with whether it collapses 50% or more, determines what the right atrial pressure is.
However, in my lab, we prefer to report the mean right atrial pressures as opposed to reporting a range like the chart above shows. As sonographers, we’ve found that this reporting of a mean RAP is much easier to remember. Please see the chart below.
IVC Collapsibility Index For Mean Right Atrial Pressure
|Normal Diameter||Collapses||3 mmHg|
|Normal Diameter||Does Not Collapse||8 mmHg|
|Dilated||Does Not Collapse||15 mmHg|
Don’t get overwhelmed when it comes to assess the IVC with echocardiography. The biggest thing is to get in there and start practicing. Locating the IVC can take a little time to figure out, but once you do, you’ll be able to do it with your eye’s closed.
Simply put, when evaluating the IVC, check and note the diameter of the IVC and then check to see if it collapses at least 50%.
Normal size/ Normal collapse = Normal IVC pressure
Dilated OR no collapse = additional evaluation.
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This is a pocket sized laminated quick reference card for cardiac sonographers and cardiologists. The card offers quick access to instructions on how to read an ECG’s, tamponade vs. cardiomyopathy, differential diagnosis, abnormal LV filling patterns, estimation of right atrial pressure, normal diastolic indices, classification of diastolic dysfunction, and much more.
This card essentially has all the main things you might quickly look for in the Reynolds handbook, but in a much smaller and lighter format.
Keep it in your pocket or do what I do and keep it on your echo machine. These cards are so inexpensive it’s something every sonographer should have…especially if you’re new.