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Okay in this next video, we're going to talk about how to grade

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coronary stenosis.

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Basically on coronary CT we

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break down the degree of stenosis From Plaque into

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the following categories mild disease.

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Which is a less than 50% stenosis.

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Another term you may hear is not obstructive

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disease.

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And then everything else above 50% or

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greater is considered obstructed disease and

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that's broken down into a few different categories. There's

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moderate disease which is from 50%

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to 69% stenosis.

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This is considered kind of the intermediate grades

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stenosis.

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It's a gray Zone.

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Usually these patients do not have severe. Ischemia.

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Related to this degree of stenosis. However, if you have multiple moderates

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stenosis, sometimes they can add up to cause severe disease

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or symptoms for the patient.

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So they're often patients who can be

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a bit of a diagnostic dilemma and may require functional IE stress

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testing for further assessment.

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Then there's a severe disease category those patients have

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stenosis that are 70% or greater.

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And in that case when we see a 70% stenosis, we

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think okay. This is a real, you know Real Deal stenosis.

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This is definitely cause some ischemia to

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the patient in the corner artery territory

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the muscle Supply by that territory all

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this comes with a big asterisk, which is that there's

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no 100% match between the anatomic

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severity and the functional severity of

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stenosis and we know that very well.

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But in general these are the categories in which

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people think about how to manage these patients and then

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finally inclusion is always obviously the most severe that's

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100% stenosis and those patients have

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very severe disease and are often may require management by

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catheterization or cabbage.

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So next I want to show you guys how we can

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look at how we can make these diagnoses based

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on the CT images.

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So first, we'll start with an example of mild stenosis. How

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do I think about this?

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Usually what I'm looking for is a nice.

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kind of robust full column of contrast

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it passes by the area of narrowing now

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a key concept here to think about is this concept of

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positive remodeling so

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Positive remodeling is the idea that the vessel itself actually

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expands to accommodate the

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plaque. And so what happens is when the vessel expands, although

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you can have a pretty big plaque like

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we see in this patient.

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That has both non calcified components here and

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a calcified component here. It's quite large and

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yet we really don't have much luminum narrowing.

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And the reason for that is that the whole vessel has

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expanded to accommodate both plaque and Lumen

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and so therefore the diameter of

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the Lumen hasn't really changed that much.

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compared to the adjacent normal segments

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now coronary CT is different from evaluation of

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carotid stenoses. You know, when we evaluate credit stenoses, they're

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very specific areas that you're supposed to

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use as you're comparator areas to determine the degree of stenosis in

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coronary CT. It's a little bit more flexible you're comparing

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the minimal luminal diameter of the

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area of stenosis to the nearest normal segment. And that's really

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up to you as a reader what you think the nearest normal segment

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is so in this case probably you would compare to say

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right here Downstream right here Upstream is

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probably a little bit too large of the comparator because you see

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a little Branch coming off. So the this is going to overestimate a

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bit the actual normal diameter. So in this case what

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we see is basically, you know, if I'm looking at this with

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my mind's eye, I see that you have a nice full calm of contrast If

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I subtract out this plaque, I don't see a whole lot of stenosis.

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And similar finding here now here you can definitely see that

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there is some narrowing but the degree of narrowing is

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it half of the Lumina greater? I'd say no we see

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again a nice big wide comic contrast multiple pixels

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wide and that is compatible with the milestones.

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Here's another example, you'll notice this patient has more heavily

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calcified disease. You can see the patient has

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quite a bit of calcium. But at this spot here that I'm

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pointing out with the arrow, you'll notice that you can see a

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big hunk of calcium, but you still have a pretty decent column

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of contrast. Now. This is a reformatted image

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that we have from our CPR. So you'll

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notice that measurement here is not in millimeters and pixels.

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That's because we're using this reformat but still certainly works

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for doing a ratio. The ratio here is

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the Luminous 6 to the normal comparator is nine. So that's

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certainly less than 50% right around 33% estimatesis.

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So one important thing that you'll notice is that compared

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to the previous lesion. Look how bright the comma contrast

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is right here. When we have a heavily calcified lesion and

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we're going to see this on some of the cases that we review you want to window

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really wide to make that calcium appear as

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small as possible and reduce the blooming artifacts as much as possible. So

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again, I'm looking for here. I'm looking for a nice big

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column of contrast that's passing by this stenosis.

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And that would tell me that most likely this is not a severe stenosis.

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All right. So now we're getting into higher grades of stenosis.

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These borderline cases. They're like right about

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50% and these honestly the ones that give you

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the most trouble we often will have to

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measure these ones just to make sure because they're kind of right on the

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borderline of where we think they may or may not be and the

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sort of obstructive category. So I find

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that you make a long axis image.

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And in this case, we see that there's a nice big calm of

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contrast and then it Narrows.

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And when we do the measurements, we get around a 50%

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narrowing. So this is right on the borderline

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of mild versus moderate disease. But

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in this case because it hits that 50% Mark we're going to call it a moderate stenosis.

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Similarly, here's another case. This patient has these are two

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views of the same lesion.

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He has this degree of narrowing right here.

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And right here if we're eyeballing it,

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you know, certainly the amount of contrast the width

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of the contrast column. I should say is decreased by approximately 50%

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in both of these lesions.

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And so in this case for this patient, these are around 50%

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stenosis.

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Just as an aside most of the time when people

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are assessing Corner CT. They're actually using qualitative assessment.

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But you know, certainly you can use numbers

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like I've demonstrate on the previous case if that

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helps you.

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This is a slightly more severe stenosis. It's still

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in the modern category. So in this case, you can see we're

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down to maybe just a few pixels across of

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contrast and significant narrowing. But

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when you do the measurements, it's not as severe

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as 70% and just eyeballing it. How do I

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know? This is not a 70% lesion. Well, it's really close but I think generally with

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this 70% lesion for me. I want to

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see just a thin string of contrast a little trickle getting

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through whereas in this case, we've got, you know

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a little bit more than that.

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And if you were to do the measurement, it would fall into that 50 to 69%

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range.

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So now when we get to 70% that's when we're talking about just a couple

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pixels across, you know, maybe even less that are

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getting through that's a 70% stenosis. So this

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would be in a severe category. You can see

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if you do the measurement, you know, you get 66% stenosis

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so we can round up to 70. So this

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is severely lesion.

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Here's another one this case just a tiny little

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bit of contrast getting through right there.

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Tiny little bit of contrast here tiny little contrast here. So that's you know

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what we see for a 70% stenosis and what you

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want to think about.

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Here's another example don't forget to diagonal. So

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we'll review some of these cases that have severe diagonal disease.

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You can see here's the contrast coming down. We've got

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some non calcified plaque here.

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And then calcified and non calcified plaque

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in this first diagonal with just a little bit of contrast getting through and

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similarly a little bit of contrast getting

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through the LEDs. So so severe disease in both the LED and

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the diagonal and it's not uncommon to get severe disease

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at these bifurcations as we see here.

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Another example, this patient has a 70% lesion

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in approximal RCA here again, just a little trickle of

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contrast getting through and then more distally actually we lose

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the contrast entirely there's some

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calcium here, but the column of

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contrast Excel itself actually stops entirely and this

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is most likely an occlusion.

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So what do we want to see for an inclusion? Well, you'd like

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to see that basically you have as abrupt termination of the contrast

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column and if it's more than a centimeter

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a centimeter or more roughly then you can say okay. I think this is probably occluded.

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Less than a centimeter than your kind of in a gray area. Sometimes things can

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look like an occlusion on CT, but then they go to

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Cath and there's actually a very very skinny amount of contrast.

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It's getting through the Lumen because cat has just much better spatial

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resolution than CT.

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So if you have a lesion less than a

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centimeter and length, then you're gonna have to say, you know, High grades stenosis

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greater than 70% versus A short

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segment occlusion.

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Here's another example of inclusion. This patient had one right here

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in the RCA. Not a very big vessel, but you can

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see that we lose that common contrast and then Downstream, it's

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actually reconstituted vehicle collaterals.

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Okay. Well, that's our review of grading of

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coronary stenosis. I hope that was helpful just an initial overview

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before we start tackling the cases and then we'll

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get a whole lot more examples with the live cases and subsequent

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videos.