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In this demonstration, I'm going to take you through

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a coronary CTA emphasizing the plane of coverage

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and the anatomy, deliberately choosing a normal

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study so that we are not distracted by pathology.

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The most important thing that you are going

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to appreciate in this is the actual normal

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anatomy but also things like field of view.

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So here's a scout topogram and the blue box

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indicates the start of the field of view and the

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white indicates the end of the field of view.

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The start is important because if you

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miss a coronary artery you can't go back.

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The end, the tendency is always to get more than

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you need. That can also be fine-tuned.

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So where do we start?

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We start somewhere in the AP window.

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The arch is a bit too high and not necessary.

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The aortic knob, which you can

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see here, is also unnecessary.

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It's somewhere below the aortic knob.

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You could have gone a bit below that.

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The first thing we do is a calcium scan.

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I'm going to maximize that.

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The calcium scan starts at that level of the arch

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and it is what's called a prospective study.

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These are standardized in terms

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of the acquisition parameters.

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They are essentially axial scans, what's known as

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step and shoot, and we look for calcium, although

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more important than calcium is just to get an

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idea of the lay of the land, and particularly if

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it's done to rule out ACS, it's a good place to

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rule out, uh, large pneumonias and lung pathology.

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And then in the same field of view, roughly, we

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have the coronary CTA, and like with anything,

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you need to have a systematic approach.

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One approach is to follow the contrast

1:56

column as it enters the right atrium.

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Notice how in the right atrium, there is

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this mixing artifact, and that's important to

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appreciate. Every time you see it, look at it.

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Understand what it looks like because you don't

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want to mistake that for pathology like thrombus.

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Conversely, you don't want to mistake a thrombus for

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a mixing artifact when it occurs in the background mixing

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artifact, which can be quite difficult to discern.

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So you kind of go all the way down, you

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look at the intra-atrial septum, which

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is nicely seen here, and go all the way up.

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You see the pulmonary artery, you see

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the ascending and descending aorta.

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One of the things that people want to do

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is rule out multiple pathologies at once.

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So for example, do a coronary CTA and rule out dissection.

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And actually, if you do a coronary study,

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you can pretty much rule out a dissection.

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We see the ascending, we see the descending.

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We don't see the arch.

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It's very unusual to have an acute

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dissection simply in the aortic arch.

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Anything can happen, but it

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would be considered unusual.

2:58

And then in the same way, you follow the pulmonary

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veins coming to the left atrium, left ventricle,

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aorta, and then you look at the coronary arteries.

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So I'm going to slow down here and look at

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the coronary arteries in the axial view.

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We, uh, radiologists, we tend to see things in the

3:15

axial view when you're looking at cardiac structures.

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That habit will obviously still be there, although we

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want to see things in non-traditional views as well.

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So here is the right coronary artery.

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The right coronary artery comes off anteriorly.

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Anterior compared to the left coronary artery, which

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comes off posteriorly, is the left, is the RCA.

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And the first thing you'll notice is the RCA, when it

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comes off, travels in a piece of real estate, this area

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here, which is known as the atrioventricular groove.

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So, right atrium, right ventricle, and

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this real estate is the AV groove.

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Actually, it's the anterior AV groove,

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indicating that there was a posterior one,

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and the RCA travels in the anterior AV groove.

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And there is a lot of cardiac motion

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in the anterior AV groove because this

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portion of the heart moves the most.

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It moves in systole and moves in diastole.

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In fact, the RCA has one of the highest

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velocities of all the coronary arteries.

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So, when a study is suboptimal because

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the shutter speed is not good enough, then

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often it's the RCA that is not well seen.

4:29

This artery coming off here from the

4:32

very proximal RCA goes posterior.

4:36

To the aorta, again it travels in a groove but it goes

4:40

posterior to the aorta, and it's the AV node artery.

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So it is an artery that supplies

4:47

the area of the AV node.

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The small artery coming off right at the beginning

4:52

of the RCA is the tiny artery, it goes anteriorly,

4:56

is either the conus or infundibular branch.

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It's usually not a very important branch

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unless there is RCA occlusion, in which

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case it becomes an important collateral.

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So now we're following the RCA, we've left the origins

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and we're now settling in the AV groove, and it's

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giving off this branch which travels anteriorly.

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These are the acute marginal branches,

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and they're not that important in terms

5:22

of stenosis detection; they're small.

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As we go here, the RCA goes around.

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And then it gives off this branch here,

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it's a continuation of the RCA, which

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supplies the posterolateral aspect of the

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heart, and that's the posterolateral branch.

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And there's another branch it gives off, this one

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here, which is in the inferior interventricular groove.

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So it starts in the AV groove and it's now

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in the interventricular groove, and this

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artery is the PDA, posterior descending

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artery, and that's to be assessed with the LAD.

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And it doesn't always come off the RCA.

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It can come off the circumflex.

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The artery which gives off the PDA and

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posterolateral branch is the dominant artery.

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So if it's the circumflex, the

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circumflex becomes the dominant artery.

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If, as so often happens, the RCA gives off the PDA

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and the circumflex gives off the posterolateral branch,

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you have a situation known as co-dominance.

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Okay, so we've gone through the RCA.

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The RCA supplies the inferior aspect of the

6:30

heart. It often supplies the papillary muscle

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and classically inferior MI can present

6:38

with heart block, papillary muscle rupture,

6:44

and

6:46

that is also a function of its dominance.

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There's a very important artery

6:51

coming off here; the left main comes off

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the left posterior cusp of the aorta

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and it bifurcates into two arteries.

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The LAD, which is this one here, and the

7:06

circumflex, and sometimes it trifurcates.

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So here's the circumflex.

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It is traveling in the posterior atrioventricular groove,

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and it has branches.

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And remember that the RCA branches are

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known as the acute marginal branches, while

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the circumflex branches are known as the obtuse marginal.

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So here's the first obtuse marginal, this one here.

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And this is the circumflex, but it's

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giving off the second obtuse marginal.

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So, the circumflex is divided into segments,

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so it's a proximal segment, and then after it

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gives off the first obtuse marginal, it becomes

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the mid segment, and then when it gives off the

7:53

second obtuse marginal, it becomes the distal.

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Notice how small it is.

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It's that small physiologically.

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It's because there's right dominance.

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And so it's constitutionally small.

8:05

It doesn't mean that it can't

8:06

get infarcted; it just means that

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its narrowing is difficult to

8:11

pick up with, because of its size.

8:15

So, an important artery is the left anterior

8:17

descending artery, which travels in

8:19

the anterior interventricular groove.

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It gives off this branch here, which is the diagonal,

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these are all named because of their appearance on CAF.

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So the first diagonal, this is the second diagonal,

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and in fact it's giving off a third diagonal as well.

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It also gives off some branches that dive

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into the septum, known as septal branches.

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They don't all, they're not always easily seen.

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So, the LAD also is divided into segments.

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Proximal is before the first diagonal.

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There's not much of a proximal in this case.

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Mid is between the first and second, so

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there's a fairly robust mid, and the distal

8:59

is after the second and the distal LAD.

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Then, as you can see, this branch here coming

9:06

off is a septal branch. The distal LAD travels

9:10

in the interventricular groove, so between the LV

9:15

and RV, and then anastomoses with the RCA distally.

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Right?

9:21

So that's your coronary anatomy.

9:23

Next we'll turn to cardiac anatomy that is non

9:26

coronary to get an idea of the rest of the heart.