Diagnosing cardiac amyloidosis with the help of CMR
How to use cardiac MRI for the diagnosis of amyloidosis–the nuts and bolts. Taken from our CME accredited course.
In this video, cardiac imaging expert Andrew Houghton MD will explain how to use CMR for the diagnosis of cardiac amyloidosis.
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[00:00:00] In this lesson, we're going to see how we can assess cardiac amyloidosis using CMR. Cardiac amyloidosis is a systemic disorder with the extracellular deposition of insoluble amyloid protein. The gold standard for the diagnosis of cardiac amyloidosis is an endomyocardial biopsy, as shown in the image on the left. But CMR can provide very helpful diagnostic
[00:00:30] information. It can identify myocardial thickening, atrial dilatation and show evidence of diffused late gadolinium enhancement in the left ventricle. This can also affect the right ventricle and the atria. We also see an unusual appearance, the dark blood pool during late gadolinium-enhancement imaging, whereas normally, the blood pool will be relatively bright. And we may see evidence of pericardial and / or pleural effusions.
[00:01:00] Let's take a look. This is a cine-CMR image showing a two-chamber view of the heart. This is the left ventricle, mitral valve, and left atrium. And this is from a 74-year-old man with cardiac amyloidosis. And we can see thickening of the myocardium, which is concentric from the whole of the left ventricle. Strictly speaking, it's not technically correct to call this hypertrophy because there's no increase in the size or number of
[00:01:30] myocytes, instead, the myocardium is thickened as a result of the deposition of amyloid protein. The patient also has moderately impaired systolic function of an ejection fraction of 38%. Here's another example of myocardial thickening. This is from an 81-year-old man with cardiac amyloidosis. This shows a cine-CMR in the four-chamber view, so we have left and right ventricles, and left and right atria.
[00:02:00] And what we see here is, again, marked concentric thickening of the left ventricular myocardium but also thickening of the right ventricle as well. A consequence of myocardial thickening is diastolic impairment and elevation of ventricular filling pressures and this increases the stretch on the atria. So, in this patient,
[00:02:30] we have cardiac amyloidosis again. We can see myocardial thickening but also we can see dilatation of the atria as a consequence of this raised filling pressures. When we perform late gadolinium-enhancement imaging, we see the diffuse distribution of late gadolinium enhancement in the myocardium, again, as a consequence of the cardiac amyloid deposition.
[00:03:00] But one other characteristic feature that we see with cardiac amyloidosis on late gadolinium-enhancement imaging is a dark blood pool. In most patients when we undertake late gadolinium enhancement imaging, we see that the myocardium is very dark but the blood pool is generally relatively bright. So, this is a normal patient, a relatively bright blood pool image. But with cardiac amyloid, we see this diffused deposition of amyloid
[00:03:30] in the myocardium but we have a notably dark blood pool, and that's a feature which is very suggestive of the presence of cardiac amyloidosis. Why does this happen? Well, gadolinium binds to the amyloid protein in the body, and as a result of this, it is drawn out of the blood pool relatively quickly, so the blood pool
[00:04:00] appears darker but normal. Another feature that is seen in cardiac amyloidosis is the presence of a pericardial or sometimes a pleural effusion. This is a cine-CMR three-chamber view, left ventricle, left atrium, and aortic valve and aortic root and we can see evidence of a relatively small pericardial effusion present. So, in summary, how do we perform CMR for
[00:04:30] cardiac amyloidosis? Well, we can use CMR to assess left ventricular wall thickness, volume, systolic function, and mass. We can also assess any wall thickening affecting the right ventricle. We can use CMR to assess the size of the left and right atria, and we can look for any pericardial or pleural effusions, and it's important to describe the
[00:05:00] pattern of myocardial late gadolinium enhancement and also the appearance of the blood pool and whether it appears darker than what we'd normally expect. If you'd like to learn more about this topic then take a look at this paper on MRI in cardiac amyloidosis published in the Journal of the American College of Cardiology Cardiovascular Imaging in 2009. So, do you already feel more comfortable
[00:05:30] with and knowledgeable about CMR? Good. Before we move on to our next module, let's try some more quiz questions.