Fetal Echocardiography - HD

Introduction

My name is Dr. Ted Dubinski, and I'm a professor of radiology, obstetrics and gynecology at the University of Washington in Seattle, Washington.

I'm going to be discussing fetal cardiac imaging today with an emphasis on evolution with regard to diagnosing fetal cardiac abnormalities.

Presentation Overview

During this presentation, we're going to discuss the background of fetal cardiac imaging, the embryology of cardiac development.

We'll discuss the fetal echocardiogram and what it entails.

I'll show you the most common anomalies detected at ultrasound.

We'll discuss common anomalies that are missed at ultrasound, and then we'll talk about the outcomes and treatments from any of the conditions that I'm going to show you.

Incidence and Importance of Cardiac Defects

Cardiac defects occur in approximately two to three fetuses out of every a hundred thousand, and that's major anomalies.

And then it's roughly eight and a hundred thousand for all cardiac anomalies.

And cardiac defects continue to be one of the leading causes of neonatal death.

And of all the fetuses born with major anomalies, nearly 25% will die in the neonatal period.

Ultrasound Sensitivity and Impact

Now, the ultrasound sensitivity for major anomalies, it used to be approximately 50%, but that really depends on where the exam is performed.

Studies that have looked at this have shown that the sensitivity is roughly 25% in community hospitals, but as high as 75% in tertiary care centers.

And this has a major impact on survival in the first week of life, with nearly 25% of undiagnosed cardiac anomalies resulting in neonatal death.

Benefits of Screening

Screening improves outcomes and it improves the detection of anomalies.

It allows the fetuses to be properly treated preoperatively, and it improves post-op survival.

It improves neurological outcomes for the fetuses and the neonates.

And the detection of these anomalies really depends on multiple views during the fetal echocardiogram.

Embryology of Cardiac Development

Now, the embryology of cardiac development can be divided into four steps.

The fetal heart begins basically as a tube, and then this tube loops on itself, and then the atrial ventricular connections are formed, the ventricular arterial alignment is obtained and then septation occurs.

And septation is the most complex and highly evolved of all the embryologic processes and only higher order mammals and birds actually undergo a septation as it occurs in human embryology.

And this is a diagram showing these processes.

So the heart begins as a tube, and then this tube actually loops on itself.

And this is what causes the basic cardiac structure to form.

And then the atrial ventricular connections are developed, and then the outflow tracks and the ventricular arterial connections are formed between the aorta and pulmonary artery.

And then in the last step, septation occurs, and these are embryologic micrographs of this process.

And you can see it starts off as a single tube, and then it loops on itself.

It almost always turns rightward.

It's very uncommon to turn leftward, and then it loops on itself.

And then the connections are established.

Evolution of the Heart

Now, if we look at the evolution of the heart from basic animals such as a worm through the fish and then through amphibians, reptiles up to mammals and birds, you can see that they start with the basic development of a tube with little connections within it, within a worm, in a fish heart, there's really just two chambers.

There's kind of a sinus where a venous return occurs, and there's an atrium and a ventricle, and there's a ventricle pushes blood basically through the body of the fish, and then it returns to the sinus venosus.

The sinus venosus will then get oxygenated blood from the gills, which goes to the atrium and the ventricle.

And this is a very primitive two chamber heart.

And you can see that this is essentially a tube that has not looped on itself at this point in time.

Now, if we move up to amphibians and reptiles, you'll see that at this point looping has occurred.

But this is really a three chamber heart where oxygenated blood is coming in from two directions and basically enters an atrial chamber and then goes into a ventricular chamber, and then goes out to the lungs or gills of the amphibian and then to the rest of the body.

And there's no distinct separation in these animals between pulmonary and arterial flow.

And this is very important not only for regulating blood oxygen levels, but for regulating temperature in these animals as well.

As you get to the reptilian heart, septation begins to occur, and then there is beginning to be a distinction between pulmonic and systemic blood flow, with complete separation or near complete separation of the chambers.

And these animals, while they're still cold-blooded and can't regulate temperature like mammals can, this is a more advanced cardiac structure than occurs in lower order animals.

And then finally, when you get to birds or mammals or human hearts, septation is complete and right-sided pulmonic circulation is completely separated from left-sided arterial circulation.

And this has allowed complete adaptation to living on land and exchanging oxygen from air rather than from water.

And when we approach cardiac abnormalities, we can keep this embryology in mind and it helps us explain a lot of the defects that we see.

Abnormalities in Looping and Situs

And the first step is looping.

And looping is what determines situs really.

And as I said, it almost always loops to the right, and this is what ends up allowing the heart to be on the left side.

If it loops the other way, then you end up with dextrocardia.

And of course, these isomerism abnormalities can result in abnormalities of the bronchi.

It can result in reversal of where the liver and spleen are located and where the atri ventricles are.

So this affects really the entire development of much of the viscera within mammals.

And you can see here the heart is on the left, and these are the bronchi.

And this is when there's situs inversus, and here you have the liver on the left, on the right, rather well the left, and then the spleen on the right, and the heart is gonna be pointing to the right as well.

So this is complete situs inversus, which just means everything is backwards.

But if you end up with something in between where it hasn't looped completely either to the left or to the right, this is when you get the situs ambiguous.

And this is associated with multiple cardiac defects.

Fetal Echocardiogram Screening Views

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 track view, left ventricular outflow track, 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.

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 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.

And this is the ventricular outflow track view.

And here 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 arteriosus, 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 tract views.

So that was a good view of the right 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.

Anomalies Missed on Screening

However, no matter what we do, there's gonna be some anomalies that are missed and anomalies that are missed include bicuspid 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 tetralogy of Fallot.

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.

Advanced Techniques in Fetal Echocardiogram

Now, the difference between a screening exam and a true fetal echocardiogram 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 is some type of bradycardia or tachycardia present or AV block.

It could also 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, the atrial ventricular valves are functioning properly.

And for example, this is the aortic arch view, 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 the presence of reverse flow in either the ductus arteriosus or the aortic arch indicates that this is a ductus dependent lesion, and that when the fetus is born, it will be a ductus 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

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 tetralogy of Fallot over the basic exam.

And then Ebstein's anomaly.

Other things that color in particular useful for, or things like VSDs double inlet or outlet ventricles, single ventricles, truncus arteriosus, and then pentalogy of Cantrell echo, masses within the heart or pericardial effusions.

Ductus-Dependent Lesions

And 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 ovale is patent.

And 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 are the aorta.

And generally you want flow out of the heart on both of these vessels, so they should be the same color.

And this is really what we're looking for on 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 what this indicates is that there's probably an aortic stenosis aortic atresia 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 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 Views and What to Look For

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.

So when we look at a four chamber view, we're looking for situs.

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, then 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 crux 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 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 left 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 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 tract 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.

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 cause the heart to have to work much harder to maintain flow through the rest of the body.

So that alignment is extremely important than 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 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 in 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 main pulmonary artery here, the ductus arteriosus, and then the right main pulmonary artery 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 arteriosus, right main pulmonary artery 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 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 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.

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 the fetal thorax.

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 tetralogy of Fallot or transposition of the great vessels.

So this single view is actually very useful for looking at outflow tract abnormalities.

And this is opposed to this view where things just don't quite look normal.

Here you have this superior vena cava and the aorta potentially, and then the pulmonary artery.

And the pulmonary artery is the one that branches.

And 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 then 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 tetralogy of Fallot.

If the aorta is small, then that's an aortic atresia.

And if there's only one vessel, then it's a truncus arteriosus.

And these are the outflow tract diagnoses that we can make.

Summary of Views

So in summary, the fetal 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 the situs, the heart and the stomach are on the same side, and the situs is normal.

And between this combination of views, we can do a comprehensive review of the fetal heart.

Septation Abnormalities

And finally, we'll talk about a class of defects that are the most difficult to visualize.

And these are septation abnormalities.

And as I mentioned, septation is far and away the most complex part of cardiac development.

And we have some photo micrographs showing the process occurring.

Initially, you start off as one chamber and ultimately a septum forms.

And this is what gives us four chambers.

This is what separates pulmonary from systemic flow.

And this is what has allowed mammals to live on land and breathe oxygen from air rather than having to extract it from water.

Now, if we look from inside the ventricle at the septum, what we see is this curved structure, and there are usually four places along the septation where defects are going to occur.

And we do very well with these inlet type VSDs and the apical trabecular type VSDs where the heart is the thickest.

And we can see VSDs here.

It's much more difficult to see the outflow type VSDs that occur in either the aortic outflow tract or what's called the supracristal VSD location.

And that's really above the aortic valve on the aortic wall.

And generally we think of four types of VSDs.

And the key is to use color flow imaging and see that there's abnormal flow from left to right during the cardiac cycle.

And this is what confirms that a VSD is present.

Now, there's three types of atrial septal defects, and the most common is the sinus venosus defect, basically, where the superior vena cava basically enters the atrium and the atrial septum isn't complete, and there's a connection between right and left atria here kind of at the level of where the superior vena cava meets the right atrium.

The other types of defects are the septum primum and then secundum defects.

And this has to do with where during cardiac development that defect occurs, septum primum defects are larger and more significant and more difficult to repair.

Where secundum defects are smaller generally, and even patency of the foramen ovale is a type of secundum defect.

And then the most severe kind of defect is the cushion defect.

And this is where the ventricular and atrial septa don't form properly.

And the crux of the heart is missing.

I mentioned this earlier.

And here's the normal diagram of the heart.

Here's the crux, and you can see the atrial ventricular valves inserting onto the septum appropriately.

Whereas in this one you can see that the crux has not formed, and usually you'll end up with one atrial ventricular valve.

There's no insertion onto anything in here.

There's just a big defect in the middle of the heart.

The ventricular septum hasn't formed, the atrial septum hasn't formed.

And this is an image from the literature showing what a large cushion defect looks like.

This is the one that's most commonly associated with Down syndrome, and it's one of the more important heart defects to pick up.

And it is very visible on a four chamber view, and that's where we see it.

And this is a large cushion defect.

Now, one thing to be aware of is that you need to see these during the cardiac cycle because in systole it may not be so readily apparent, but as now these are the outflow tracts, aorta, pulmonary artery here.

But as we come back to the four chamber view here, you can just see there's nothing in the middle of this heart.

There's one atrial ventricular valve, and this is a large cushion defect.

Having a cushion defect doesn't mean that you don't have outflow tract abnormalities as well.

But you can see the big defect in the middle here, and it's much more apparent on realtime imaging than it is on a still image.

And here's just another one.

There's just not a lot in the middle of this heart.

And we can see as we come through the heart here, there's just nothing here.

There's just a big defect.

This is a large cushion defect.

This is low in the trabecular septum in the ventricles, and then there's usually an atrial septal defect as well.

And this is how we make the diagnosis.

Now, I mentioned that there's four types of VSDs, and this is what a VSD would look like, and these are the ones we pick up fairly readily.

We only have about a 50% sensitivity for all VSDs, and this is because of where they are.

But these low septal defects we tend to pick up.

And what we're really looking for is this little color flow jet going from left to right.

The pressure in the left ventricle postnatally is much higher than it is in the right ventricle, at least normally.

And if there is a defect, there'll be a little jet that occurs during systole from left to right.

And this is really what we're looking for.

So here's the VSD here, and then on color flow imaging, here's the defect here.

Okay, now, in utero, pressure is more balanced between the right and left.

And the flow may not necessarily be from left to right, but once the baby is born and it starts breathing, pulmonary vascular resistance drops significantly, right-sided pressure drops.

And then there's usually flow from left to right postnatally.

And these are the different defects.

These are the ones we see quite readily.

These are the ones that are the most difficult.

They're high up on the aortic outflow tract, and they're just very difficult to see mainly because this is a curved structure and sometimes the alignment is difficult to get.

And the real problem is that you can make every one of these look abnormal.

If you're not aware of this various VSDs with the jet, these are in neonates.

This is postnatally after they're born.

And this is very classic of what these look like.

Another VSD here, axial view shown left and right ventricles, and there's a big VSD here.

And then as I mentioned, the outflow tract VSDs sometimes called perimembranous VSDs or supracristal VSDs are much harder to detect.

And this is where that occurs.

And you can see a little bit of a flow jet there.

You really, this is a postnatal exam and you can see the much more readily in utero.

It's much more difficult to detect.

This type of VSDs are not lethal anomalies.

They're not ductus dependent lesions generally, as long as the outflow tracts are normal, if it's big enough, a neonate could go into congestive heart failure from the left to right shunting from the VSD.

But generally, these are not cyanotic type VSDs that are gonna cause hypoxia in a neonate, and this is a high one, these are outlet VSDs or supracristal type VSDs.

And you can see the little flow jet occurring almost at the level of the aorta.

Okay, you're still in the left ventricular outflow tract at this level.

And the jet actually does go back into the right ventricle here.

And that's why by definition this is still a VSD.

Outflow Tract Abnormalities

Tetralogy of Fallot

Now, tetralogy of Fallot is generally characterized as hypoplasia of the pulmonary artery.

And if we look at this three vessel view, we've discussed this view here.

Here's the pulmonary artery.

It's originating to the left and anterior to the aorta.

So the orientation is normal.

This is a little bit of right atrium.

I mentioned sometimes you don't see the SVC particularly that the shot is more angled through the atrium, and that's what we're seeing here.

But you can see that the pulmonary artery is much smaller than the aorta, and that's really the diagnosis.

Now these have a VSD as well, and that's a little more subtle.

And this is an outflow tract type VSD, and you can see the septum is not in continuity with the anterior aortic wall.

And the aorta has moved rightward slightly so that it now overlies the septum.

And we kind of approximate how much of the aorta is over the septum.

So I would call this a 50% overriding aorta over a VSD.

And this is very characteristic of tetralogy of Fallot on the schematic.

You can see the septum is normal and the pulmonary artery is normal, whereas in a tetralogy, the pulmonary artery is smaller than the aorta.

And there's a VSD as well.

And that's really how you diagnose this abnormality.

If you get severe enough and this pulmonary outflow tract is very small, you'll get reversal of flow in the aorta in the ductus arteriosus to maintain flow to the aorta here.

And then it can become a ductus dependent lesion.

And these are cyanotic defects.

Because the pulmonary artery is small, there's not a lot of blood going to the lungs.

And so when the baby is born, it isn't oxygenating blood as appropriately as it should.

And this leads to cyanosis and fetal hypoxia.

Okay, we talked about concordance between atria and ventricles, and then concordance between the outflow tracts and the ventricles as well.

And here this is almost like a three vessel view with ductus pulmonary artery to the left and anterior to the aorta, and then superior vena cava there.

And again, another tetralogy of Fallot, and these can be difficult to see.

What you're really looking for is that the pulmonary artery is small.

So here's the aorta, here's the aorta there, and there's a defect right there in the outflow tract right there.

It's difficult to see, but I think you can see it, right?

I'll try one more time here. There it is, right there.

And that's the VSD part.

Now in utero, here's the aorta and the pulmonary artery.

And at this point in time, the pulmonary artery isn't that small, and this is why we miss tetralogy of Fallot sometimes it's not necessarily that visible in utero.

Another view, this is a four chamber view, and as we look up, you can see that, you know, it's going very fast.

There's a defect actually in the aortic outflow tract here, but it's very subtle and that's why these can be missed sometimes.

Here's another view. This is more of a sagittal view.

So we're starting off with right atrium.

Here's the left ventricular outflow tract, and right there there's a defect.

It's very subtle.

But that's the VSD part of a tetralogy of Fallot.

Okay, one more video loop here.

And we can see as this plays the four chamber view, you can see there's a big defect here.

Okay, this is high. This could almost be an endocardial cushion defect.

It's not uncommon at all for the VSD to actually be larger than just a VSD and be a cushion defect and have tetralogy of Fallot.

So those can certainly coexist.

Double Outlet Right Ventricle and Transposition

Now, if the aorta can move rightward and overly a VSD, it is possible for the aorta to actually move so far rightward that it actually originates from the right ventricle as well.

And this is just the severe form of aortic overriding and known as a double outlet right ventricle.

And a lot of times when this occurs, there can be transposition of the great vessels as well.

And this is one where the aorta is coming outta anterior to the pulmonary trunk.

So this is a double outlet ventricle with transposition, and that's a very common association as well.

Okay? And then this is schematics basically showing this ventricular arterial connections.

And these are outflow tract type VSDs.

When we have a transposition, the aorta and pulmonary artery will be parallel to each other.

Unfortunately, that happens in textbooks, but it doesn't always happen in real life.

And frequently there's other more complex cardiac defects that obscure this parallel arrangement of the aorta and pulmonary artery because looping hasn't occurred properly in the orientation of the heart may be wrong.

So we may not see the classic abnormality.

The key thing to diagnose transposition is to recognize that the aorta is coming off to the left of the pulmonary artery now rather than the other way around, which is appropriate.

And on this video, I think you can see, well, it's very fast.

There's only one ventricle here, really.

And so both outflow tracks are coming off the one ventricle.

And on this video loop we're starting off, here's the superior vena cava coming into atrium, and then you can see the aorta coming off here.

And this is really coming off the right ventricle, and you'd have to be oriented and see other views to know this.

But that is really what tells us that.

There's a transposition here as well as a double outlet ventricle.

We're not seeing the other outflow tract here on this particular video loop.

Here's a four chamber view, and as we sweep through this up, now, you can see there's one outflow and here's the other outflow, and they're both coming off the same chamber, which is really the right ventricle.

I know this is very fast, but that's really what we're looking for here.

So not only is there a double outlet ventricle here, but these are transposed because the aorta is coming off to the left of the pulmonary artery.

Okay? And this is what we're showing here.

This is the anterior aorta.

So this is a transposition.

And then here when we're doing angiogram, the left ventricle is opacified, and yet it fills the pulmonary artery that by definition is transposition.

And then here's one, here's a transposition.

You can see the aorta is to the left of the pulmonary artery.

Pulmonary artery coming off left ventricle, aorta coming off right ventricle, and that's a transposition of the great vessels.

Now, transposition of the great vessels comes in two varieties, the D transposition and L transposition.

And the D form is really when the outflow tract and the arteries have actually switched.

And this is a ductus dependent lesion because you have two parallel circuits that are not connected to each other in any way.

So blood flow comes out the left ventricle, goes out the pulmonary artery and then comes back the pulmonary veins back to the left atrium and to the left ventricle.

So you have circulation of blood from the left ventricle back to the left ventricle, and there's no intermixing here on the right side.

The systemic side, blood flow is coming out of the right ventricle.

It comes out the aorta, it goes to the body, comes back through the superior and inferior vena cava into the right atrium, and then it's into the right ventricle again, and now it's going out to the body.

So you have systemic flow that's completely separate from pulmonic flow, and so you need either a VSD or you need a patent ductus arteriosus to connect these two systems to each other.

So this defect can lead to some of the worst forms of cyanosis and hypoxia postnatally of any of the defects.

Now, the L transposition is less severe.

That just means the ventricles are switched, but the rest of the circuit actually is normal and they're in series they're not in parallel, they're actually in connection.

And these don't result in the degree of hypoxia that the D transposition results in.

And this is a transposition.

So you see this is the aorta coming off the right ventricle, and you can see that.

And then this is a little harder to see.

Here's the pulmonary outflow tract here and here, and it's very unusual to actually see the bifurcation into the right and left main pulmonary artery.

This tells us the alignment is abnormal anyway, and this is coming off the left ventricle.

So this is, as we sweep through, you can see right ventricle aorta, left ventricle pulmonary vessels, and the best way, and there's even a little VSD here, the best way to make this diagnosis is to do sweeps through the heart and then go frame by frame and determine which outflow tract is connected to which ventricle In this particular case, this VSD is necessary because this is what connects the two circulations to each other and allows oxygenation of the neonatal blood.

And here's just another view of this aorta coming off the right ventricle.

And here's the pulmonary artery, and this is left and this is right.

So these are transposed, and you really have to look at these very carefully and figure out what's connected to what they're very difficult to see otherwise.

Okay, and this is a schematic of that, and this is just a severe aortic overriding over a VSD.

Truncus Arteriosus

And in this particular case, only one outflow tract is formed.

There's not a separate aorta and a separate pulmonary artery, and that's a truncus arteriosus.

So these are the outflow tract abnormalities.

These are the most difficult ones to diagnose.

Our job when we screen for these defects is strictly to determine if there's reversal flow in the ductus or the aorta, and that will tell us whether this is a lethal defect and whether further evaluation is needed.

And then these can be referred to the appropriate center where these are gonna be treated postnatally.

And again, this is a schematic showing various types of truncus defects and a lot of combinations are possible.

And the bottom line is there's just one large outflow tract that we see flow is in the right direction here.

It's coming out of the heart and then down the descending aorta.

And you can see two little pulmonary arteries coming off of here.

And this is a truncus, and this is a sweep showing from the four chamber view as we come up that you can only see one outflow tract.

There. It is one large outflow tract, probably a large VSD or cushion defect in here as well.

I think there is a cushion defect right there.

One AV valve, it's a complex congenital heart abnormality, takes a multi-stage repair.

This is showing the color flow proving that the two chambers connect to each other, and that this truly is a large VSD or cushion defect.

And then as we sweep towards the outflow tract, you can see just one vessel here, and the flow is coming out of the heart.

This is blue in this case showing that it's coming away from the heart, meaning out of the heart.

And so again, the ductus dependent lesions, tetralogy can be depending on the degree of pulmonary hypoplasia.

And then transposition most certainly is, especially if there's no ASD or VSD.

And these are the ductus dependent lesions.

And this is extremely important, and this is probably the single biggest contributor to decreasing neonatal mortality, is to recognize what is a ductus dependent lesion and then treating the neonate with prostaglandins or other medications as necessary to keep the ductus patent.

And again, this is the alignment when septation occurs.

This is the normal septation with the AV valves straddling the septum.

But there are various complex heart defects where both inlet valves are in the right ventricle or even more rare.

Very rare is when both inlet valves are in the left ventricle.

So these are the inlet abnormalities.

You can have a double outlet ventricle.

You can also have a double inlet ventricle.

And this has to do with looping and then the symmetry of where septation occurs.

And this is what results in a hypoplastic left heart.

This is what results in a hypoplastic right heart, and then it's a matter of where the valves are situated.

And this of course increases the complexity of the repair of these defects.

And again, this is another schematic of that.

This is the atria, the AV valves basically being balanced here and appropriate or overriding to one side or the other.

So this is just another diagram of the same thing.

And you can see that if you look at this particular cine loop, you'll see that the AV valves are both feeding basically into one ventricle here.

So this is really the right ventricle.

And you can see both AV valves.

So that's a double inlet valve.

Ebstein's Anomaly and Other Defects

Now finally, Ebstein's anomaly is a slightly different type of defect, and this is basically an inferior displacement of the mitral valve or the tricuspid valve insertion.

And this results in what's an enlarged right atrium.

Some people refer to this as an atrioventricular.

But this is a big defect.

And in effect, this diminishes right ventricular outflow, and it diminishes cardiac output on the right side.

And this causes right sided heart failure.

And here you can see the right atrium.

And instead of the AV valve inserting here, which would be normal, it's displaced apically significantly.

And this is really what Ebstein's anomaly is more than the right atrium enlargement.

It's this displacement of the valve that's significant.

But bicuspid aortic valve is very difficult to diagnose in utero, we usually don't see it normal tricuspid valve.

Sometimes you might see this fish mouthing in the aortic valve.

This is a postnatal exam.

It's easier to see here, and that's a bicuspid aortic valve.

But prenatally, this is very difficult to diagnose.

It's associated with coarctation of the aorta, and that's a significant thing to look for.

And if you happen to see a coarctation of the aorta, then you look for the bicuspid aortic valve since they are associated.

M-Mode and Arrhythmias

I mentioned that M mode is part of the fetal echocardiogram, and this is what an M mode strip would look like when we look for arrhythmias.

And you can see these are the ventricular contractions here.

These are atrial contractions, these very subtle ones.

As we angle, we try to get an angle through the heart where we can see the atrium and the ventricle in one plane, and one-to-one correspondence as normal.

If you're seeing more atrial contractions than ventricular contractions, then that's an AV block.

If it's too fast, greater than 175 beats per minute, that's tachycardia.

If it's too slow, less than 90 beats per minute, that's a bradycardia.

And sometimes you can just get the feeling that the heart is just beating away way too fast.

And if you look at this cine loop, you can just see this heart is hardly contracting and it's beating away.

This was about 200 beats per minute.

And there's a pericardial effusion was actually causing heart failure in this fetus.

Big heart. This is just a huge heart.

And this was an interesting case.

This was a twin, and the other twin had died in utero.

And this twin is then actually perfusing the other twin, and the heart gets enlarged.

And this baby starts going into heart failure because it's got such increased afterload resistance that it's actually pumping two circuits, both twins.

And this heart was just huge.

It's occupying the whole thorax here.

Tumors and Other Issues

Tumors are very uncommon of the heart.

And the one we usually see is a rhabdomyoma, and you'll see that as an echogenic mass.

And a lot of times there's lots of little echogenic masses on these that we may or may not be able to resolve.

And there is an association with tuberous sclerosis on these.

So if we see this, we'll look at the kidneys for angiomyolipomas, and then we'll look at the head as well for periventricular calcifications.

And this is associated with a seizure disorder.

And in addition, if this chamber is full of tumor and it can't fill with blood, then this fetus is at risk for going into heart failure when it's born, because basically there's no inflow occurring here.

So it's kind of a preload reduction that results in heart failure.

And then there are other defects that are not exactly heart defects per se, but you can have a large anterior abdominal wall defect where the heart is actually located outside of the body.

And there is a thing called ectopia cordis, which is the heart being located outside of the body, but there's a large anterior abdominal wall defect.

So you have an omphalocele, the diaphragm doesn't form properly.

The pericardium obviously hasn't formed correctly since the heart is outside and you have heart defects associated with these, and these can be repaired.

In the old days, it wasn't possible to repair these, but now they can be repaired.

Here's another one. The heart is out, the liver is out.

Here's a large anterior abdominal wall defect, and this was a pentalogy of Cantrell, another one, a lot of polyhydramnios in this particular case.

Here's bowel, here's liver, a lot of things sticking outside of the abdominal body.

Conclusion

So in conclusion, there is a difference between screening heart views, which is what we all do, and each view has a specific thing that we're looking for.

But a true fetal echocardiogram is a slightly different exam that includes M mode Doppler and color flow imaging.

It's extremely important to take cine clips, and this is how we make most of our diagnoses.

The single most important thing to know is which lesions are the ductus dependent lesions and how we go diagnosing these and why we miss defects.

We're never gonna be a hundred percent accurate.

It's seeing these and unfortunately these are so complex that sometimes we just can't see everything that's wrong with the heart in utero.

And I think it's very interesting that most of these heart defects do reflect the embryology of cardiac development evolutionarily as we evolve from worms and ultimately fish, amphibians and reptiles.

Thank you very much.