0:00

Okay. In this video we're gonna talk about, uh,

0:04

specifically annular measurements that are used for optimal device sizing and

0:08

selection. Uh,

0:09

these form part of the more global aortic root assessment that's performed with

0:14

cardiac ct. Um, and we've divided this up into a couple different videos. Um,

0:18

so another important part of the aortic root assessment that we won't discuss in

0:22

this video is identification of high risk anatomy. And those additional, uh,

0:27

points are gonna be discussed in the, uh, measurements of the aortic root video.

0:31

Um, and those include things like low coronaries, neuro sinuses, and, um,

0:35

calcification as well. Um,

0:37

so here in this video we're gonna focus on the annulus,

0:41

which is the most important, um, measurement, uh,

0:43

for deciding on what device can be used, uh, in the patient. So first,

0:48

uh, before we get into how to measure the annulus,

0:51

I just wanna take a quick step back and talk about why we measure the annulus

0:54

with ct. Um, and that really has to do with, uh,

0:58

the concept of paravalvular leak, um, also known as paravalvular regurgitation.

1:03

And this is, uh, really simple. Conceptually,

1:05

it's an incomplete seal between the transcatheter valve and the aortic annulus.

1:09

So there's a gap between the edges of the device and the annulus.

1:13

And that gap allows blood to flow retrograde from the aorta into the left

1:18

ventricle. So, uh,

1:19

we know from prior studies that this is associated with increased mortality and

1:23

poor functional status. Um,

1:26

and so we want to avoid paravalvular leak as much as possible.

1:29

There's also some association with valve and annular calcifications that disrupt

1:33

apposition of the stent to the annulus. Um,

1:36

and we're gonna actually talk about that in a different video. Uh,

1:38

the annular calcification video. So here's just some data, um,

1:43

from the, uh, previous trial. This is the partner trial, um,

1:46

two-year follow-up data. Uh, and the thing I just wanna point out here, uh,

1:50

is that this is mortality death from any cause, uh,

1:53

and patients with no paravalvular leak had significantly reduced

1:58

mortality compared to any patients with either mild or severe, uh,

2:02

paravalvular leak. Um, and this, uh, slide here shows that, um,

2:06

even among patients with mild versus moderate disease, they both,

2:10

those groups still tended to do fairly poorly, um,

2:13

sort of hammering home this point that we really wanna avoid paravalvular leak

2:17

as much as possible.

2:19

The reason I'm talking about this is that paravalvular leak, like I mentioned,

2:22

is really behind the whole push to perform CT for TAVR assessment.

2:26

Originally in the early TAVR trials, echo was used to size the annulus, uh,

2:31

and they found that the echo measurements, which you see up here, um,

2:34

which use a single dimensional measurement and then extrapolate them into the

2:38

area of a circle, um, were inadequate. Um,

2:41

and that's because the echo measurements basically perform this type of

2:45

diameter,

2:46

and they extrapolate to a circle when the real aortic annulus is an oval shaped.

2:52

And, um, these, uh,

2:53

mathematical assumptions made by echo resulted in undersizing of the devices.

2:58

And

2:58

That undersizing led to increased paravalvular leak.

3:02

This was tested in a randomized control trial,

3:05

and that trial showed that the paravalvular leak was twice as frequent in the

3:08

echo sized group versus the CT size group. And, you know,

3:12

basically from that day forward, uh,

3:14

CT has been the test of choice for sizing devices for tavr.

3:19

So now in order to understand, uh, the aortic annulus and how to measure,

3:23

we need to understand the aortic root anatomy. Um,

3:26

and basically the aortic root is this part of the heart that connects up to the

3:30

aortic itself. And we have this wide part called the sinuses.

3:34

And then within the sinuses you have the aortic valve cusps. These cusps, um,

3:38

insert on the aortic annulus and the,

3:41

the annulus is considered the lowest point where these cusps insert. Um,

3:46

and you sort of take a virtual ring from those, uh, lowest points.

3:50

I'll show that in another image in a second.

3:53

So here's sort of a, a short axis, um,

3:57

reconstruction from, uh, a CT compared to a long axis reconstruction.

4:02

To give you an idea of what we're talking about, um,

4:04

if you take this short axis reconstruction here on the right,

4:07

you can see the three different valve leaflets.

4:09

And then as we march inferiorly to towards the annulus,

4:13

you see these leaflets start to disappear. And then at the level of the annulus,

4:18

that's when the leaflets transition to being completely outside of your field of

4:21

view. Uh, and now you see just this rounded, um,

4:25

actually oval shape structure here,

4:26

and the leaflets are attached just above that point.

4:29

And so this is our annulus and this is, uh,

4:32

basically where the device is gonna sit.

4:35

And this determines the boundaries of the device itself. Um,

4:39

so here's one other image, and this is from the literature.

4:42

I think this is a nice, uh, figure. It's a lot of colors,

4:46

so it can be a little confusing. And anybody who's colorblind, I apologize. Uh,

4:49

this is hard to evaluate. Um, I give the reference down here below,

4:53

but these red lines, uh,

4:55

are the actual edges of the attachment of the cusps of the aortic valve

5:00

to the aortic root. And you can see that they have a,

5:03

a high commissure up here between the two valves, and then they swing down low.

5:07

Um, here this basal point and this green thing is the

5:12

annulus, which is made by the,

5:14

the ring form between all the three different basal attachment sites.

5:17

And so when we go through the case, I'll show you how to do this, um,

5:20

and attain this annular measurement with ct.

5:23

So what are the measurements that we get? We tend to get the maximum diameter,

5:27

uh, from, uh, along the long axis of this oval shaped annulus,

5:31

and then the perpendicular, um, as well as the perimeter and the area.