Fetal Echocardiography

Basic Screening Views for Cardiac Abnormalities

As we move on to doing the fetal echocardiogram,
when we screen for cardiac abnormalities,
we do several views
and the basic views of the four chamber view,
right ventricular outflow tract view,
left ventricular outflow tract,
and then there's what's called a three vessel view,
which I'll show you, which I find particularly useful.
And then we can add an aortic arch or ductal arch view.

Now, this is for screening
and most of us, on every fetus that we examine, we try
to get as many of these views as possible.
And if we can't get the views, we will note that
and bring the patient back to attempt to get the shot,
later, during the course of the development, usually two
or three weeks after the initial exam.

But this is not a fetal echocardiogram at this point.
This is just a basic screening exam
of what we're looking for.

Normal Four Chamber View

And here you can see a normal four chamber view
of the heart, and you can see the septum here.
And, we're looking, to see this is the,
the right ventricle here, right ventricle here,
left ventricle here, left atrium, right atrium.
You can see the heart is pointed
to the left at about a 45 degree angle.
And this is what a normal four
chamber heart would look like.
And we're looking for different structures
on each of these views.

Ventricular Outflow Tract View

And this is the ventricular outflow track view.
And here we're semi, we're demonstrating that the
aorta is coming off the left ventricle.
Okay? So in this outflow track view,
what we're really seeing is from the anterior chamber
of the right ventricle, we can see the pulmonary artery,
coming out and then bifurcating into the ductus arteriosis,
and then the left main pulmonary artery.
And you can see the aorta in the middle of the image here.
And this is what we're trying
to demonstrate on these outflow Trent views.
So that was a good view, of the right
of ventricular outflow tract,
and you could see that it was
perpendicular to the aorta here.

Now, if we can obtain all of these views,
generally we can do fairly well detecting major
cardiac abnormalities.

Limitations and Missed Anomalies in Screening

However, no matter what we do,
there's gonna be some anomalies that are missed
and anomalies that are missed include,
by cus aortic valves, mild degrees of aortic atresia,
which are just very difficult to see.
Asds and VSDs are very difficult to pick up in utero.
And our sensitivity for VSDs, is roughly 50%.
And this is because we're good at seeing the large VSDs.
And as I'll show you later in the course of this,
presentation, we don't see the VSDs
that are higher up the outflow tract
that are more difficult to see.
And early on, in the embryologic period,
it's sometimes difficult to detect tetrology a fall.
This is basically pulmonary hypoplasia,
and oftentimes we can't detect that
until the third trimester,
and it isn't really visible, early on.
So we miss those sometimes.

Difference Between Screening Exam and Full Fetal Echocardiogram

Now, the difference between a screening exam
and a true fetal echocardiagram is the addition
of these three techniques to the exam.
One is M mode, which is used
to look at fetal arrhythmias,
to determine if there's some type of bradycardia
or tachycardia present or AV block.
It could also tell,
give us information about the presence
of pericardial effusions and chamber sizes,
and then the addition of color flow
and doppler imaging, to the exam.
This is utilized to determine what direction,
blood flow is occurring within the great vessels,
which is key, to diagnosing certain abnormalities.
And then the Doppler exam can help us determine whether
aortic stenosis or regurg is present
or if the other valves,
atrial ventricular valves are functioning properly.

Example of Aortic Arch with Color Flow Imaging

And so, for example, this is the aortic atrophy,
and you can see this is coming out
of the left ventricle here.
And this is inferior vena cava, superior vena cava
and the aortic arch.
And we put color flow imaging on this,
and we can see that flow here is in blue, meaning
that it's coming down away from the
heart or out of the heart.
And that's extremely important.
If there's an aortic stenosis flow will be reversed in
the aortic arch, and this is
how blood will get to the fetal brain.
And these are ductus dependent lesions.
And so the presence of reverse flow in either the ductus
arteriosis or the aortic arch indicates
that this is a ductus dependent lesion,
and that when the fetus is born,
it will be abductus dependent, neonate
and, prostaglandins
and medications will be necessary, to maintain patency
of the ductus, until the defect is actually repaired.
And this is just another view showing
that flow is coming out of the aorta here
and coming out of the ductus here.

Common Abnormalities Detected on Fetal Echocardiogram

So common abnormalities
that are detected on the fetal echocardiogram,
that we generally want
to pick up are large endocardial cushion defects,
hypoplastic left or right heart,
transposition of the great vessels.
This helps us improve our detection
of tetrology fall over the basic exam.
And then Epstein's anomaly.
Other things that color in particular are useful
for are things like VSDs double inlet
or outlet ventricles, single ventricles, truncus,
arteriosis,
and then penology of cantrell echo,
masses within the heart or pericardial effusions.

Key Considerations for Fetal Cardiac Defects

And so the single most important thing we want
to know about any fetal cardiac defect is whether
it's lethal or not.
And that primarily depends on whether it's a ductus
dependent lesion as I mentioned previously.
And the other thing is whether the foramen oval is patent.

Normal and Abnormal Flow in Aortic Arch and Ductus

And so here's a view of the aortic arch,
and you can see in this with the fetus being, spine up,
this is in red, so the flow is coming out of the arch
and then down the descending aorta.
So that's normal flow. Here's the ductus here, the aorta,
and generally you want flow out of the heart on both
of these vessels, so they should be the same color.
And so this is really what we're looking
for in this particular view.
We can see that flow is actually coming out of the heart,
in the ductus,
but flow is actually reversed in the aortic arch.
And so what this indicates is
that there's probably an aortic stenosis, aortic reia here,
and that flow is coming out of the ductus
to the descending aorta,
and then flow is reversed in the aorta.
And this is how blood is getting to the fetal head.
And so therefore, this is a ductus dependent lesion,
and if the ductus closes postnatally,
this fetus will die.
So this is really the single most important thing
that we want to know, when we do a fetal echocardiogram.

Specific Findings in Screening and Fetal Echocardiogram Views

Now, when we look at each of the views
and the screening exam,
and then subsequently a fetal echocardiogram, we're looking
for specific things on each view.

Four Chamber View: What to Look For

So when we look at a four chamber view, we're looking
for theus.
The heart should be on the left. We're looking for the axis.
This should be a 45 degree angle
between the sternum and the spine.
We're looking for the number of chambers to make sure
that we see four chambers here,
and they should be roughly the same size.
Now, the left ventricle appears a little bigger than the
right due to the presence of the moderator band.
We wanna make sure that the left ventricular apex is a
little more apical in location than the right ventricular
apex because of this moderator band.
And if these look like they're the same size,
then it's actually abnormal.
And then finally this structure in the middle of the heart,
is called the crus of the heart.
And this, evolutionarily is the most complex part
of cardiac development.
And we want to make sure
that the septum is completely formed and that the atrial
and ventricular septums connect to each other
and that the atrial ventricular valves connect
to the septum subsequently.
And as long as we can see this, cross in the middle
of the heart, then we know, that development is normal
and there's multiple cardiac defects
that we can detect on this single view alone.
Sensitivity is probably 50%.
Just getting a single view like that
size of the heart matters.
It should be roughly a third
of the entire thoracic diameter.
If the heart looks too big, then either the chest is small
or the heart is too large,
and that's a clue that something is occurring.

And when we look at these exams,
are there really four chambers here?
And if you look at some of these, these look
to be the same size, which would actually make it abnormal.
And it's very difficult to see
that there's actually atria and ventricles here.
So this doesn't look particularly normal.
And then if we look on this view,
which is obtained from the literature,
you can see it looks like there's just one chamber here.
And this is the type of defect
that we can see when we look at our four chamber view.
And so here's another one. Here's the apex of the heart.
And you can see the left ventricle doesn't quite make it all
the way to the apex on this particular view
or on this particular view.
Okay, so this is abnormal.
This left ventricle is small,
and this is actually the beginnings
of hypoplastic cleft heart.
And this is subtle, but this is one thing
we're looking for on these views.
As opposed to these images
where you can see the left ventricle really almost
approximates the anterior chest wall, of
The fetus. And
it really does look like it's
longer than the right ventricle.
This is normal again because of the moderator band.
And you can see it on this view.
It doesn't matter what position the heart is in,
you can frequently get these views.
And here's a, a nice, view where you can see
that these chambers look like they're the same size.
This left ventricular chamber,
does not approximate the anterior chest wall.
And again, this is the beginnings of hypoplastic left heart.
And these are just more views showing
that the heart should be pretty
much in the middle of the chest.
If you draw a line from sternum to spine, it should pass
through the left atrium.
And this particular case, you can see the heart is displaced
by a mass, probably a diaphragmatic hernia,
or in this particular case there's a mass,
displacing the heart, posteriorly
and rightward, abnormal cardiac axis.
This is a clue, because it occurs during looping
and if the axis is abnormal, there's a very high association
with outflow tracted abnormalities.
So just seeing that the axis is off actually gives you a
clue that the outflow tracts may not be normal even though
you're not really imaging the outflow tracks.
So again, this is normal roughly 45 degrees
from sternum to spine.
This one is too horizontal.
It's closer to 90 degrees than 45 degrees.
This one hasn't rotated at all.
So this is almost zero degrees, it's just in parallel, more
or less with the spine and the sternum here.
And if you look at this, you can see
there's only two chambers.
There's no septum here on this particular, heart at all.
So this is very abnormal.

Left Ventricular Outflow Tract View

The second view we tend to get
after the four chamber view is the left
ventricular outflow tract.
And what we're really looking for on this view is to see
that the aorta is aligned with the septum.
So the intraventricular septum should be a continuous line
with the anterior aortic wall,
and that's what we're looking for here.
And there should be no disruptions
or defects within this line.
And if there is a defect in there's A VSD,
and if there's a VSD, then the question is
how far rightward is the aorta displaced over the ventricle?
And that's what's referred to as aortic overriding.
Now this line is extremely important,
to maintain laminar flow, during,
ventricular systole
as blood is being ejected from the left ventricle into the
aorta and any disruption that occurs in that,
will diminish blood flow
and caused the heart to have to work much harder
to maintain, flow through the rest of the body.
So that alignment is extremely important.

Right Ventricular Outflow Tract View

Then the right ventricular outflow tract is the
other view we obtain.
And what we're looking for in this is that the size
of the aorta and pulmonary a artery are the same
and that the pulmonary artery is anterior
and left of the aorta.
So if this is the left ventricular outflow view
with the septum and the anterior aortic wall,
as I mentioned, as we angle slightly more superiorly,
you'll get a view where,
a vessel is coming out of the right ventricle.
And you can see, the, the main pulmonary artery here,
the ductus arteriosis,
and then the right main pulmonary art coming behind,
the aorta here.
Sometimes you can see the coronary
arteries actually on these exams.
And here's what this looks like.
This is the right ventricle here.
This is the main pulmonary artery ductus arteriosis,
right main pulmonary artery in, in the aorta.
And you can actually see the valve leaflets
on this particular view.
And sometimes you'll get the coronary
arteries, as I mentioned.
And so it's extremely important one to see that the aorta
and pulmonary artery are more or less the same size
and that two, they're at right angles to each other.
So while we're seeing this in longitudinal,
we're seeing this in cross section.
And this tells us that these are perpendicular to each other
and that this is a normal alignment, multiple views.
This is a sagittal view showing the ductus coming out
of the more anterior chamber, which is the right ventricle,
and this is the proper orientation for that.
Here's another view, the ductus arch.
And so this is right ventricle.
This is the pulmonary artery and ductus from here to here.
And then this is the descending aorta.
Now, that's as opposed to the aortic arch where
the great vessels,
can be seen coming off the aortic arch.
And this is coming off the more posterior chamber now,
as opposed to the ductus.

Three Vessel View

Now if we move axially slightly more superiorly,
you can obtain what's called a three vessel view.
The three vessel view,
is a very helpful view as we look across.
Now, the fetal thax,
what you're seeing is superior vena cava, aorta,
and pulmonary artery.
And the orientation of these is
that the pulmonary artery should be to the left of the aorta
and superior vena cava,
and it should originate more anteriorly than the aorta
and they should be more or less the same size.
And if you have this view
and you can see both of these vessels
and you have this alignment,
then you know the outflow tracks are normal
and you've excluded the presence of either aortic atresia
or tetrology of fallo or transposition of the great vessels.
So this single view is actually very useful,
for looking at outflow track abnormalities.
And this is opposed to this view
where things just don't quite look normal.
Here you have the vena cava and the aorta potentially,
and then the pulmonary artery.
And, the pulmonary artery is the one that branches.
And so you can always determine which one that is.
And here's another view.
And you can see this is actually originating anterior closer
to the chest wall, than the aorta.
Okay? And then frequently you may get the superior vena
cava, or sometimes this is angled inferiorly
and you might see right atrium here.
That's very commonly seen, in various examinations
of the heart, and that's okay.
It's really the orientation
between these two that's important.

Now this is a CT scan through the thorax,
and this is showing the normal orientation of the
Pulmonary artery in the aorta
and superior vena cava with pulmonary artery being anterior
and to the left of the aorta.
This is an abnormal orientation
and you can see that the aorta is to the left
of the pulmonary artery
and that it's anterior to the pulmonary artery.
So this would be a transposition
of the great vessels actually.
And this is what we're looking for.
Now, if the pulmonary artery is small,
that's a tetrology of fallow.
If the aorta is small, then that's an aortic atresia.
And if there's only one vessel,
then it's a trun of arteriosis.
And these are the outflow tract
diagnoses, that we can make.

Summary of Fetal Cardiac Exam

So in summary, the fetal cardiac
cardiac exam is a combination of multiple views
and we're looking for specific things on each view.
This is the four chamber view, which should be discussed,
left ventricular outflow tract views,
and then the right ventricular outflow tract view.
And then this is the three vessel view.
And between all of these views,
and this is the stomach just showing that theus, the heart
and the stomach are on the same side
and the sinus is normal.
And so between this combination of views,
we can do a comprehensive review, of the fetal heart.