0:01

Next, we're going to review cardiac anatomy.

0:03

As you see, I've got an axial image here through

0:05

the mid-heart, and this is going to be the

0:08

starting point for our discussion of all the

0:10

various cardiac chambers, all the various portions

0:13

of the heart and the way that they're named.

0:16

And this is going to, uh, apply throughout

0:19

the entire cardiac MRI mastery series.

0:22

So, first, when you look on this axial set of

0:25

images, you see, uh, multiple cardiac chambers.

0:29

You've got the left atrium, which is located

0:31

posteriorly here, right in front of the esophagus.

0:35

And the left atrium, obviously, is

0:37

where the pulmonary veins arise.

0:38

You can see one of the right

0:40

inferior pulmonary veins right here.

0:42

This line here

0:43

designates where another pulmonary

0:45

vein should be, but it's out of plane.

0:47

So, the left atrium is separated from the left

0:48

ventricle by the mitral valve, which lives right here.

0:51

And the left ventricle is this U

0:53

shaped ventricle here, more anterior.

0:56

And that's the most important and what we

0:58

really often focus a lot of our attention on.

1:01

Right ventricle ends up more

1:02

anterior, just below the sternum.

1:05

And then the right atrium here, which is on top of the

1:08

superior vena cava and below the inferior vena cava.

1:11

Right atrium and right ventricle are

1:12

separated by the tricuspid valve.

1:15

So, on this axial image, we can really see

1:17

all the various cardiac chambers, get a sense

1:19

of the size, whether any of the chambers are

1:22

enlarged, and then also start setting up our

1:25

planes for the remainder of our acquisition.

1:28

Um, so, if you're new to cardiac MRI and you're

1:32

starting cardiac MRI new at your practice,

1:35

then it's going to be really important for you

1:37

to work with your technologist to make sure

1:39

that they can get the right imaging planes.

1:42

And so, therefore, as radiologists, it's

1:44

really important that we know how to arrive

1:45

at those imaging planes ourselves so that

1:47

we can help, uh, teach the technologists as

1:49

they go through, um, uh, cardiac imaging.

1:53

So, the first imaging plane that we get in

1:55

the acquisition of cardiac MRI sequences is

1:58

the vertical long axis or two-chamber view.

2:00

And so, the way this works, um, you take

2:03

your axial plane and you just draw a

2:05

line right through the mitral valve here.

2:08

You want to be right in the center of the mitral

2:10

valve, and then you use as your other important point

2:13

of reference, the center of the apex of the heart,

2:16

and then just draw a straight line through them.

2:18

That's going to be the plane that you use

2:19

to define the vertical long axis view.

2:22

And so, you don't have to

2:24

oblique the coronal view at all.

2:26

You can just go straight to

2:27

this vertical long axis view.

2:29

And this is the first important

2:32

imaging plane in cardiac MRI.

2:35

Okay, on this two-chamber view, we see the

2:37

left atrium and the left ventricle separated

2:39

by the mitral valve, which is right here.

2:42

This also allows us an opportunity to

2:44

start talking about the different parts

2:45

of the heart and the nomenclature.

2:48

So, on the next slide, what you're going to see

2:50

are the different parts of the cardiac anatomy,

2:53

in particular, in reference to the left ventricle.

2:57

So, the base is the part of the heart which is

3:00

closest to the mitral valve and to the atria.

3:04

The apex is the part of the heart that's

3:06

closest to the sternum and the chest wall.

3:09

And then the anterior wall is the part of the

3:11

heart up here, which is right up against the lungs.

3:14

And the inferior wall down here is actually the

3:16

part of the heart that's sitting on top of the

3:17

diaphragm, and you can just see a little bit of liver.

3:21

Underneath, that's the inferior wall.

3:24

So these are used universally throughout

3:26

the description of the left ventricle.

3:28

And in particular, the base to apex gradient

3:30

here often comes up when we're talking about the

3:34

positions of different things within the heart.

3:37

Now, for the next step in defining the cardiac

3:40

imaging planes, you take your two-chamber long axis

3:44

view and just like we did with the axial images,

3:47

we drop a point here at the mitral valve in between

3:51

the leaflets, right in the center of the mitral

3:53

valve, and then another point here at the apex of

3:55

the heart, and we draw a line connecting those dots.

3:58

From that line, we then create perpendicular slices.

4:01

Just like we see here, and those perpendicular

4:04

slices we create in a stack going from base to apex.

4:07

And these define our short axis images,

4:11

which we're going to see on the next slide.

4:13

So these are the short axis images

4:14

on the right-hand side of your image.

4:17

Short axis images are really the workhorse.

4:20

This is what we use for defining the quantification

4:23

of the heart using specialized software.

4:26

Remember how we talked about tracing

4:28

the endocardial borders as such?

4:31

When we do those endocardial borders and even

4:33

epicardial border tracings, then what we can do is

4:37

we can add up all these slices and eventually come

4:41

up with end-systolic volume and end-diastolic volume.

4:46

Using those two together, we can actually, together

4:49

we can come up with an ejection fraction as well.

4:51

So that all comes from these endocardial borders.

4:54

The epicardial border is actually

4:56

useful for defining the cardiac mass.

4:59

So these short axis images are really, really important

5:02

and probably the most important, at least in terms

5:04

of quantification, uh, when you perform cardiac MRI.

5:07

Now, if we look on the next set of images, we're

5:09

going to actually see the various parts of the

5:12

heart and their definition on the short axis images.

5:15

We already talked about the

5:16

anterior wall and the inferior wall.

5:18

The anterior wall being up here next to the lungs and

5:20

the inferior wall being right here next to the liver.

5:23

And then what we now see, which we didn't

5:25

see on that initial two-chamber view, we

5:27

see the septal wall and the lateral wall.

5:29

The septum is easy.

5:30

That's the part of the heart which basically

5:32

separates the right and left ventricles.

5:35

Okay.

5:35

So, super easy to evaluate.

5:37

The lateral wall, a little more difficult.

5:40

It's basically the part of the heart that's out here,

5:42

right up against the lung, and really defined by

5:45

kind of the cross-section formed by the lines through

5:48

the septum and through the middle of the heart.

5:51

So you end up with these four quadrants

5:52

of the heart: anterior wall, septal

5:54

wall, lateral wall, and inferior wall.

5:56

And these are the main parts of cardiac anatomy.

5:59

One other thing to note is that there are actually

6:02

an additional set of definitions of two additional

6:06

types of walls that you might encounter in the

6:09

formal American Heart Association nomenclature

6:12

of the heart, and they're actually subdivisions

6:15

of the lateral wall and the septal wall into the

6:18

anterolateral wall and the inferolateral wall.

6:25

And then the same goes for the septum.

6:26

We have the subdivisions of the anteroseptum up here.

6:31

And the inferoseptum down here.

6:34

So these are all the various names of the walls

6:36

that you can encounter in clinical reading.

6:39

Also, the names that we should be

6:40

using to describe locations of various

6:42

abnormalities that we find on cardiac MRI.

6:45

Okay, so next steps for defining the cardiac planes.

6:48

From this short axis view, what we're going

6:51

to do is we're going to place a plane that

6:52

intersects the anterolateral papillary muscle right here.

6:57

and through the corner of the

6:59

right ventricle right here.

7:00

And that's the angle between this free wall

7:02

here, which is parallel to the sternum, and the

7:06

inferior wall here, which is parallel to the liver.

7:09

And that intersection there becomes point one, and

7:11

this papillary muscle becomes point two, and then

7:13

you should have a plane going right through them.

7:16

That plane should also intersect the middle

7:17

of the septum, which we see right here.

7:20

And then if you get that all correct, you

7:22

should have a view something like this,

7:23

your four chamber view on the right.

7:25

I'll have to say that this is the trickiest

7:27

of all the planes to get right because you

7:29

have to have all these things lined up.

7:31

And even when you do that,

7:32

sometimes it's not quite right.

7:33

And you have to do a little bit of adjusting.

7:36

Also, what's not shown here is that from the

7:38

base to the apex, you want to have the similar

7:40

type of arrangement that we saw with the short

7:43

axis and the two chamber views where you're

7:45

through the middle of the mitral valve at

7:47

the base and through the apex of the heart.

7:50

So, if you do that all correctly, you'll get

7:51

something like this four chamber view here.

7:54

Okay, on this next set of four chamber

7:56

images, now we see the cardiac anatomy that

7:59

we've visualized on this four chamber plane.

5:59

One other thing to note is that there are actually

6:02

an additional set of definitions of two additional

6:06

types of walls that you might encounter in the

6:09

formal American Heart Association nomenclature

6:12

of the heart, and they're actually subdivisions

6:15

of the lateral wall and the septal wall into the

6:18

anterolateral wall and the inferolateral wall.

6:25

And then the same goes for the septum.

6:26

We have the subdivisions of the anteroseptum up here.

6:31

And the inferoseptum down here.

6:34

So these are all the various names of the wall

6:36

that you can encounter in clinical reading.

6:39

Also the names that we should be

6:40

using to describe locations of various

6:42

abnormalities that we find on cardiac MRI.

6:45

Okay, so next steps for defining the cardiac planes.

6:48

From this short axis view, what we're going

6:51

to do is we're going to place a plane that

6:52

anterolateral papillary muscle right here.

6:57

And through the corner of the

6:59

right ventricle right here.

7:00

And that's the angle between this free wall

7:02

here, which is parallel to the sternum, and the

7:06

inferior wall here, which is parallel to the liver.

7:09

And that intersection there becomes point one, and

7:11

this papillary muscle becomes point two, and then

7:13

you should have a plane going right through them.

7:16

That plane should also intersect the middle

7:17

of the septum, which we see right here.

7:20

And then if you get that all correct, you

7:22

should have a view something like this,

7:23

your four chamber view on the right.

7:25

I'll have to say that this is the trickiest

7:27

of all the planes to get right because you

7:29

have to have all these things lined up.

7:31

And even when you do that,

7:32

sometimes it's not quite right.

7:33

And you have to do a little bit of adjusting.

7:36

Also, what's not shown here is that from the

7:38

base to the apex, you want to have the similar

7:40

type of arrangement that we saw with the short

7:43

axis and the two chamber views where you're

7:45

through the middle of the mitral valve at

7:47

the base and through the apex of the heart.

7:50

So, if you do that all correctly, you'll get

7:51

something like this four chamber view here.

7:54

Okay, on this next set of four chamber

7:56

images, now we see the cardiac anatomy that

7:59

we've visualized on this four chamber plane.

8:02

You see the posterior chambers.

8:04

These are the atria, the right

8:06

atrium, and the left atrium.

8:08

And then you see more anteriorly the

8:10

right ventricle and the left ventricle.

8:12

The left-sided chambers are

8:13

separated by the mitral valve.

8:15

The right-sided chambers are

8:16

separated by the tricuspid valve.

8:19

In addition, we can use this opportunity to

8:21

talk about the different parts of the heart.

8:22

Again, the septum is seen here between the right

8:26

ventricle and the left ventricle and the lateral wall

8:28

on the lateral side along the surface of the lung.

8:33

Now, finally, I'm going to introduce one

8:34

more concept in terms of nomenclature of

8:38

the various parts of the heart, and that's

8:40

the base, mid cavity, and apex thirds.

8:42

And so when we talk about the heart, we

8:44

usually talk about dividing the heart up into

8:46

thirds and the base to apical gradient.

8:48

And so we have a basal third, a mid

8:51

cavity third, and an apical third.

8:53

And it turns out that these are

8:55

actually pretty easy to identify.

8:57

And we use the papillary muscles as our guide.

9:00

So you can see there's a papillary muscle

9:01

right here, and oftentimes we'll have

9:03

another papillary muscle right here.

9:06

And so the mid cavity is really defined by the area

9:09

around the slices where you see the papillary muscles.

9:13

All the slices where you don't see papillary

9:16

muscles as the cavity is getting smaller, and the

9:18

base is all the slices that are above the papillary

9:22

muscles as the slices, the cavity size is getting

9:25

larger all the way up until the point where you see

9:28

the mitral valve and you're in the right atrium.

9:30

So that's pretty easy.

9:32

We use similar nomenclature for the right

9:33

ventricle base kind of mid apex as well.

9:36

We call the right ventricle, we call

9:38

this the anterior wall or the free wall.

9:41

We describe the inferior wall

9:42

just like the left ventricle.

9:44

And often we also describe a more anterior

9:47

wall above just like with the left ventricle.

9:50

Next, we're going to talk about the

9:51

three chamber view or LVOT view.

9:54

This view is defined from the short axis and is

9:57

really the last kind of most important bread-and-

10:00

butter view that we're going to use in cardiac MRI.

10:03

The three-chamber view you see on the right is a really

10:05

great view for looking at the mitral valve, which is

10:08

right here, and the aortic valve, which is right here.

10:13

So on this view, you can see really

10:16

nicely the interaction between the

10:17

mitral valve and the aortic valve.

10:19

You can look for aortic regurgitation, which would show

10:21

up as low signal coursing retrograde through the aortic

10:24

valve, or mitral regurgitation, which would show up as

10:27

low signal going posteriorly through the mitral valve.

10:31

The other thing you can look for here is

10:33

you can see areas of turbulence in the

10:36

left ventricular outflow tract, which is

10:37

this region just below the aortic valve.

10:39

That's called the LV outflow tract.

10:42

And if you see any turbulent flow through

10:44

this region, that might suggest a

10:46

diagnosis such as hypertrophic cardiomyopathy.

10:49

How do we get to this imaging plane?

10:51

Well, you start with a short axis view

10:53

and you make a plane that's perpendicular,

10:55

basically to our four-chamber view.

10:58

If you're at the base of the heart, what

11:00

you're going to see is that the aortic

11:02

root is going to come out just like that.

11:05

And you want to create your plane going

11:07

right through the middle of the aortic root.

11:10

And heading obliquely through the center of the heart.

11:12

So your two touch points are the middle of

11:14

the aortic valve and the center of the heart.

11:16

And you use that to create the two points

11:18

to define the line that goes that way.

11:20

Of course, you want to be lined up

11:21

with the apex from the base to apex.

11:24

And once you do that, you should get a view here

11:27

where you get nice visualization of the aortic

11:28

valve up top and the mitral valve down below.

11:32

And again, this is called the left ventricular

11:34

outflow tract or three-chamber view.

11:36

And it's really great for looking

11:38

at the aortic and the mitral valves.