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In this next video, we're gonna talk about vascular access planning.

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And so what is the role of CT in vascular assessment? Well,

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the main thing is that we want to use CT to select the optimal access route,

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and far and away the ileo femoral route is preferred, meaning that, that,

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you know, the interventionalists want to use the, the, uh,

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femoral arteries to place their catheters, uh, in order to deliver the device.

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Um, and in general, if you have, uh, decent looking vessels, uh,

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with diameters that are six millimeter or greater, this should not be a problem.

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Uh, for all of our newest devices, however,

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you often run into patients who have heavily calcified or disease vessels and

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diameters that are, you know, five millimeters, uh, or less. And in those cases,

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you think about different alternative approaches.

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So subclavian arteries would be the next best thing. Uh,

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but then there are also other approaches, carotid and radial have been used,

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although honestly, you know,

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now you're getting down to some pretty small diameter.

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So it depends a bit on the type of device you're delivering.

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Some are a little smaller delivery systems than others. Um,

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and then there's direct aortic and transapical.

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Direct aortic actually is going between the ribs into the as and aorta and

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placing the device that way,

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whereas transapical are going between the ribs and going right through the apex

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of the heart, uh, and placed in the device that way.

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So those are clearly much more invasive, and I obviously avoided, uh,

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if at all possible. So what are our steps in vascular access evaluation?

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When we're performing the CT scan,

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we wanna first perform an overall assessment and look at the just general degree

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of aortic calcification. If patients have cabbage grafts,

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usually wanna mention them, um,

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and mention whether you see that they're open or, uh, occluded. Um,

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and then you talk about any other incidental findings besides the cayo grafts,

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you know, aneurysms, dissections,

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anything like that that you think might impact their ability to use the vessels,

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um, for their catheters. Uh,

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and then we go through a segmental vessel evaluation and that, uh,

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segmental evaluation has three components. We talk about the diameters,

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that's the most important,

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and then we usually talk about tortuosity and calcification.

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So we grade aortic calcification qualitatively, um, non mild, moderate severe.

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And then there's this thing called the porcelain aorta, which I'll talk about.

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So, um,

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there's no real grade sort of guideline out there for what differentiates mild,

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moderate, or severe. Here's what we use. We tend to use,

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if there's a little bit of flex here and there, but not a ton. We go for mild,

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um, if it's starting to get continuous,

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but there's still areas that are spared here and there we call it moderate.

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And then if it's pretty much there's calcification throughout,

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we call it severe.

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And then the porcelain aorta is this concept that there's this almost like

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eggshell calcifications of the entire aorta, uh, throughout. Um,

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and the reason this is important,

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it's actually a little bit historical in the world, in,

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in surgical aortic valve replacement, this porcelain aorta is a big no-no,

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it's really hard, or, uh,

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it's basically a contraindication to performing surgical aortic valve

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replacement. The reason being that you can't, uh,

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cross clamp the aorta in a porcelain aorta. Um, and so

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These patients in the old days were ones that were preferentially sent to tavr.

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Um, now that we know that TAVR is appropriate in, in both high,

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middle and low risk patients, it's really less of an issue. But still,

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if you see it, you certainly wanna mention it.

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Here's another case of por aorta with somebody with severe tiff few aortic

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calcifications.

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There are no real guidelines that exist as far as like how to deal with these

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other things like aneurysms or dissections or,

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or what if you see a lot of nasty ulcerative plaque. Um, but you know,

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we mention them, um, because, um, if it looks, you know,

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concerning then the interventionalists may, um,

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decide to use a different access, uh, route.

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So here's an example of an incidental aneurysm that we saw in a patient that

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looks like a ular aneurysm, probably from, um,

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penetrating athero Chloric also doesn't look very good. You know, you,

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you wouldn't necessarily want to put a catheter through here.

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I suspect this wall is fairly thin and, and at risk for, um, atrogenic injury,

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this was a case with the big polypoid plaque, um,

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and the descending thoracic aorta. And so in this case,

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they avoided going through, uh, this, you know,

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you worry that you might send off an embolus or something,

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and instead they went for direct aortic access. Uh,

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this is a patient bunch of graphs, very, very complicated.

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Certainly wanna be careful putting catheters through this patient.

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So they actually went with transapical access instead. Um,

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so what about the diameter measurements themselves? Well, how do we do that? Uh,

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you use a three D imaging platform, um, and you know,

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there are a ton of different three D imaging platforms out there. And, um,

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you know, they will universally have the ability to create curve planar,

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reformatted images from those.

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You wanna perform short axis measurements that are perpendicular to the vessel

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wall. Um, and we generally,

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you want to make sure to measure the inner luminal diameter, um,

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and get the minimal diameter as well as the perpendicular.

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There are some occasions where the three D platform isn't really working.

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Maybe you have poor contrast opacification,

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or that's a really heavily diseased vessel.

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You can do manual double oblique measurements as well for the vessel diameters

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if you need to. We take measurements at multiple levels,

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basically at each segment, abdominal aorta, common iliac, external iliac,

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common femoral, and so on. Our, um,

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approach is that we don't necessarily measure the subclavians if the iliacs look

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good. Um, however, if there's iof femoral disease, uh,

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meaning that the diameters are less than six millimeters,

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then we'll go ahead and measure the subclavians as well, uh,

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and provide those in our report. Ideally, like I had mentioned before,

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if the diameters are six millimeter and grayer,

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usually those vessels are good to go.

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Five millimeter is kind of a borderline case. Sometimes that can still be used,

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uh, sometimes not, depending on the degree of calcification and the size of the,

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um, device that needs to go in. Here's just the example, um,

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of this curve planer analysis. With this particular type of software,

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we place a C point proximally and we placed a C point distally and the software

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was able to connect the dots, um, and make this curve planer, uh,

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stretched image of the vessel. And from that we create some short

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Axis fuse and then do the vessel diameter measurements. And so this is, um,

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basically the approach that you take for, um,

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any of these particular types of software that you use. Um,

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this is the same for the subclavians. Remember I mentioned that, uh, doing a um,

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saline flush is really important to limit the amount of artifact in the adjacent

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veins. Um, and that's, uh,

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very helpful for getting a good curve plan or analysis of the subclavian

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arteries. If you don't have that, then uh, you can run into trouble. Uh,

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just be aware that oftentimes we,

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we scan these patients with their arms up and oftentimes we'll get some kinking

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in the subclavian arteries when the arms are up. Um,

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don't measure this as the minimal area of stenosis. This is a positional thing.

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Um, you know, you wanna look for the, uh, diameter elsewhere. So, uh,

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other things that we mentioned. So,

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so I mentioned that we always grade the diameters,

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but then we also assess tortuosity and calcification.

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How do we assess tortuosity? Well, um,

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there's no commonly accepted method for quantification of tortuosity. Um,

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and so the analysis is really qualitative.

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We have kind of some rules of thumb that we use, um,

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where if it's a mild bend, we'll call it a mild tortuosity,

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sort of like a 90 degree ish kind of thing,

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you put in the moderate category and then more of a hairpin turn we call severe.

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And so here's an example of, of some cases, this hairpin turn here,

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obviously that's severe.

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And then somewhere around like the 90 degree ish range we consider moderate

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calcification.

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These are important to mention because there's greater risk of vascular injury.

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Again, this is a qualitative assessment. There's no accepted grading scale.

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In the literature, you might find that different scales that are, you know,

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people, you know,

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qualitatively use based on the degree of circumferential and circumvent of the

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vessel. And here's just an example of that. So here you have calcification,

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less than 50% of the vessel diameter, and then here, 50, 75 and so on.

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That's a way to do it. I to say that the only problem with this is that,

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you know, if you have a, a very short segment with, with the severe, you know,

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circumferential calcification, but then the rest of the vessel looks good,

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is that really severe calcification.

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So I think you have to combine this analysis also with the total volume of

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calcium throughout the vessel and, and give your best assessment.