Assessing aortic stenosis with the help of cardiac MRI (CMR)
Learn how to assess aortic stenosis with the help of CMR. Taken from our Cardiac MRI Essentials Course.
In this short video, cardiology mastermind Andrew R. Houghton, MD will take you through the steps to assess aortic stenosis using cardiac MRI (CMR).
This video was taken from our CME accredited Cardiac MRI Essentials course taught by Andrew Houghton, MD–Cardiac imaging specialist and head of cardiac imaging at Grantham & District Hospital.
Check out the Cardiac MRI Essentials course now!
[00:00:00] In this lesson, we're going to learn how to assess aortic stenosis using CMR. Although CMR can play an important role in the assessment of aortic stenosis, echocardiography, nevertheless, remains the cornerstone for this. Echocardiography is widely available, is relatively inexpensive, and provides us with detailed hemodynamic assessment about the aortic valve. Nonetheless, CMR offers us valuable
[00:00:30] information regarding aortic valve morphology and could be particularly helpful for identifying bicuspid aortic valve, particularly when echo images are suboptimal. Like echocardiography, CMR can provide information not just on valve morphology but also hemodynamic information on flow velocity and therefore, allow the calculation of peak gradient. CMR does provide more accurate information about aortic anatomy,
[00:01:00] left ventricular hypertrophy including the calculation of left ventricular mass and also precise quantification of left ventricular systolic function. So, let's take a look at some examples. Let's begin with the assessment of valve morphology. This is a still frame, from a cine-CMR image. This is a three-chamber view with the left ventricle, here, the mitral valve, and the left atrium, and we have the left ventricular outflow tract, here, we have the aortic
[00:01:30] valve and the aortic root. And in this view, we can inspect the aortic valve cusps, as in echocardiography in the parasternal long-axis view. We have the right coronary cusp, here, and we have the non-coronary cusp, here. We can assess cusp fitness. In this patient, the cusps are thickened and in the cine image we can also assess cusp mobility, as we'll see in a moment. We can also measure aortic root
[00:02:00] dimensions and we traditionally do this at the level of the aortic valve annulus, at the level of the sinus of Valsalva, and at the sinotubular junction. So, here's the cine-CMR image, from which that still frame was taken, so we can now see everything in motion. So, we can now assess the mobility of the aortic valve cusps and we can see how those thickened cusps are very restricted in their mobility. We can actually see the
[00:02:30] forward flow, the ejector flow going through the valve and entering the aorta during systole. We can also look at the left ventricle and we can assess left ventricular size and systolic function. We can also look for any evidence of aortic regurgitation. There's no significant regurgitation present in this particular patient. Here's another view of the aortic valve. This is known as the coronal left
[00:03:00] ventricular outflow tract or coronal LVOT view. This is a view that's unique to CMR. It doesn't really have an echo equivalent. And in this view, we have the left ventricle, here, we have the aortic valve, just here, again, with thickened cusps. And we have the aortic root and ascending aorta, just here. In using this view, we can again, measure the aortic root dimensions at the level of the aortic annulus,
[00:03:30] at the sinus of Valsalva, and the sinotubular junction. It should be remembered that the normal values for aortic dimensions are different, depending upon whether we measure them in the three-chamber view that we saw moments ago or whether we measure them in the coronal LVOT view, here. The European Society of Cardiology publishes normal ranges for both sets of views. And here's the cine image, from which that still frame was taken. So again, we have the left ventricle, we have
[00:04:00] the aortic valve and aortic root, and again, we can appreciate that the aortic valve cusps are thickened, with markedly impaired cusp mobility. And then we have the short-axis view of the aortic valve, where see the aortic valve. The aortic valve in this image is just, here. This is a still frame taken from the cine image and we can see if that's a pseudo bicuspid aortic valve. We have two fused
[00:04:30] cusps, here, which are joined by median raphe, and then we another cusp, here. In terms of identifying the cusps, we can either look for the origins of the coronary arteries or we can use the interatrial septum, which is just here. And we know that the cusp, which is adjacent to the interatrial septum is the non-coronary cusp. So, the interatrial septum is, here and this cusp is the non-coronary cusp.
[00:05:00] And that makes this the right coronary cusp, towards the patient's right, and this is the left coronary cusp, towards the patient's left. So, non, right and left. We can also see the orifice of this valve. This is a stenosed, pseudo bicuspid aortic valve. And we can also undertake direct planimetry of the orifice to calculate the orifice area. Here is the cine-CMR image, so again, we have the aortic valve
[00:05:30] seen on [unintelligible 00:05:31]. We have these two fused cusps, with a median raphe in between, and we have the non-coronary cusp, here. And we can see that this pseudo bicuspid aortic valve is significantly stenosed, with a greatly reduced valve orifice area, during systole.