Evaluating the left atrial appendage for a thrombus is important in various settings. It’s most commonly performed, though, in patients in atrial fibrillation who are scheduled for cardioversion.
In this short lesson taken from our TEE Essentials course, cardiac imaging expert Andrew Houghton, MD will teach you how to obtain the mid-esophageal LAA view to assess the left atrial appendage, quantify emptying velocities, and look for thrombus and spontaneous contrast with the help of transesophageal echocardiography. If you want to learn how to obtain a full TEE exam with all its views and measurements, make sure to check out our TEE Essentials course!
[00:00:00] In this lesson, we're going to learn specifically how to assess for left atrial appendage of transesophageal echo. Now, we're going to begin with the mid-esophageal two-chamber view with the left atrium, the mitral valve, and left ventricle. And you can just see the left atrial appendage a bit at the edge of the screen, here. Now, the anatomy of the left atrial appendage is quite variable, and so the transducer angle at which
[00:00:30] it is best seen can be quite variable too. Nonetheless, the common feature of all the left atrial appendage views is that they're obtained at the mid-esophageal level. Now, I'd suggest that you start your search, of the left atrial appendage, with a transducer imaging plane angle of approximately 90 degrees. Somewhere in the region of 90 to 110 degrees will usually be a good starting point for your search.
[00:01:00] An imaging plane angle of approximately 90 degrees will give us a two-chamber view of a heart of the left atrium, mitral valve, and left ventricle. And we can just see the left atrial appendage coming into view at the edge of the sector. And in order to optimize the view, make sure that you're focus position is centered on the left atrial appendage and also start to turn the probe so that we swing across the sector
[00:01:30] and start to bring the left atrial appendage towards the center of the sector. That will give us a slightly more centered view, like this one. And also reduce the depth of the sector, so that we enlarge the appearance of the appendage on the screen. And in this view, we can start to appreciate the full extent of the appendage but do remember that it can be a multi-lobed structure. Up to five lobes have been identified at
[00:02:00] autopsy and so we will need to assess the appendage in multiple imaging planes, to make sure that we've seen every part of it. When we're looking at the appendage, look carefully for any evidence of thrombus, or indeed any spontaneous echo contrast, in the left atrium or in the appendage itself. Be careful not to mistake small pectinate muscles, which are small ridge-like muscles around the edges of the appendage,
[00:02:30] for thrombus. Here, we've adjusted the transducer plane angle, it's now at 75 degrees and we should always freely adjust the angle, firstly, to inspect the appendage in multiple planes but also to ensure that we've opened up the appendage as best we can to avoid foreshortening. Again, you can just appreciate some pectinate muscles within the appendage itself in this image.
[00:03:00] Adjacent to the appendage, we have a left upper pulmonary vein and in between the two, we have the posterolateral ridge, which is sometimes known as the ligament or fold of Marshall. It's also been known as the Warfarin ridge because some people have mistaken this for thrombus and incorrectly recommended anticoagulation with warfarin. Again, we can adjust the depth of the imaging sector to really maximize
[00:03:30] the size of the left atrial appendage on the screen, to ensure that we've inspected it very thoroughly. When we really zoom in on the left atrial appendage, we can start to appreciate the anatomy, not just to the appendage but also posterolateral ridge and we can see that the ridge itself has a rather bulbous end to it. And this has given it the common nickname of the Q-tip sign because the posterolateral ridge looks a little
[00:04:00] like the end of a Q-tip. When we assess the left atrial appendage in multiple views, we should aim to obtain at least two orthogonal views, in other words, two views of approximately 90 degrees to each other. So, here is one view obtained at 48 degrees, which clearly shows the left atrial appendage and then here's the orthogonal view obtained at 138 degrees, which shows the same appendage but at a 90-degree
[00:04:30] orthogonal plane. And in this particular view, we can very clearly see the pectinate muscles, along the edge of the appendage. Again, be careful not to mistake these for thrombus. Once you have assessed the anatomy of the left atrial appendage, we should apply color Doppler and this can help us to assess the full extent of the appendage. The presence of color within the appendage makes it more easy
[00:05:00] to see exactly how far it extends. We should also perform pulsed wave Doppler to measure the emptying velocities of the appendage. And to do this, we should place the pulsed wave Doppler sample volume approximately 1 cm inside the orifice of the appendage. In this case, the emptying velocity is 0.8 m / s. Now, low appendage emptying velocities below 0.2 m / s
[00:05:30] are associated with increased risk of thrombus and embolism. Whereas, normal emptying velocities greater than 0.4 m / s indicates a higher chance of sustaining sinus rhythm after cardioversion for atrial fibrillation. In our assessment of the left atrium and its appendage, we should always lookout for presence of spontaneous echo contrast. The swirling smoke-like appearance in the left atrium,
[00:06:00] which is consistent with a prothrombotic state. The presence of spontaneous echo contrast is associated with a higher risk of thromboembolic events. And this spontaneous contrast can extend into the left atrial appendage itself and in this case, a patient with mitral stenosis, we're seeing not just spontaneous echo contrast in the left atrium and the appendage but also layers of thrombus, which have built up within the
[00:06:30] appendage itself.