Ultrasound of the Fetal Heart What You Should Know - HD

Introduction to Ultrasound of the Fetal Heart

Hello, I'm Dr. John McGahn. I'm from the University of California Davis Medical Center that's located in Sacramento, California.

I'm gonna talk to you about the topic of what everybody should know about examination of the fetal heart.

Today what I'm gonna talk about is ultrasound of the fetal heart, what everyone should know.

And part of this is obviously we all want do a better job in examination of the fetal heart.

We really don't miss anything but probably a secondary motivation, certainly within the united states.

And that secondary motivation within the United States is there's a number of lawsuits that have been brought up against those performing obstetrical ultrasound.

Many of these just have to do with missed defects.

Verdicts are very high in these 1 million, $2 million and higher and they end up for a variety of causes, most of which are anomalies that could probably be detected on a four chamber view of the heart.

The PASS Acronym for Four-Chamber View

There's such a acronym called pass and I'm gonna talk a little bit about that.

And that's really the start.

And we start with the four chamber view of the heart and I've actually put that down to four separate letters.

And the first is P for position or the sinus of the heart, A for axis of the heart, then s for the size of the heart and the ventricles.

And then finally another S for is that septum intact or not.

Position of the Heart

So if you took this case here in which you had the stomach almost midline, this is some of the liver here, the portal vein is midline, what would your be your diagnosis?

I've listed five different things that you could think here and Ashley, when I've shown this to people, they usually come up with the wrong diagnosis.

This happens to be cyto ambiguous or axia.

And axia falls under the syndrome where there's either asplenia or there's polys Nia.

And if we look down here, the instance is very rare, but there's marked increase of abnormalities of the fetal heart.

Even sto in versus itself may have only a 5% instance of abnormalities of the fetal heart.

So if we look at this case, what it ended up being was axia and there was a AV canal seen here in real time as well as uh, color and power doppler.

Axis of the Heart

Secondly, we're gonna look at the axis of the heart and this has been known for a long time and when we look at that we have to make sure that we have one complete rib on each side.

If you look at that axis, it should be about 45 degrees.

This has been around for 20 years.

So if you look here, you should make sure you see a rib on each side.

The spine is posterior from then you draw a line from the spine anterior.

That should be about 45 degrees.

The right atrium should lie on the right side of that line.

This is a case that is very difficult, but it is not this case.

But another case we published in the Journal of Ultrasound in UM, medicine, and this is actually case of early Epstein's anomaly.

That's where the tricuspid valve is.

And if you look here, it'd be a very difficult diagnosis to make, but you can see the axis is probably not quite normal.

We wait four weeks and by four weeks later you can see here the axis is quite abnormal.

We're starting to get dilatation of the right atrium.

This is a case with a in uteral fetal ultrasound showing enlarged right atrium and an abnormal axis Four weeks later we can see this uh, quite easily where there's dilatation of that right atrium and the axis is very abnormal.

Extra cardiac abnormalities can either cause the cardiac access to be less or greater than 45 degrees.

This simple case here where the heart is on the left side, we draw a line anterior to posterior.

We go ahead, it should be 45 degrees.

We see the heart at the right atrium is displaced to the left side of that line.

And in fact this is a case of CPAM or CAM.

So, uh, intrathoracic non-cardiac masses will cause the axis of the heart to deviate.

Certainly there are other etiologies where the heart will be less than 45 degrees.

I've listed a couple of these here.

Size of the Heart

Next we'll look at the size of the heart and then I'm gonna look at the size of the ventricle.

So size of the heart.

We can look at this, we can look at it subjectively and that's probably as good as anything.

So I think the heart looks normal 'cause I've seen a number of hearts over and over again.

So I could say that heart size is about normal.

We can use rules of three or we can use a cardiac circumference where the cardiac circumference to the chest circumference should be less than about 0.5.

So we can take the cardiac circumference, we can take the chest circumference.

That ratio should be less than about 0.5 or as I like to do, take rules of three.

We get the heart here, we get another, if you think of it, a circumference or a coin here.

And we could put three coins in here.

There's a little room for part of this coin that overlaps here into this part.

You know some of the other part of this coin that overlaps here or back into here.

And that would be your rules of three.

Or if you look at this case, you can now say, whoa, this hard subjectively is too big.

If we did a cardiac circumference from here compared to here, it certainly would be too large.

And this basically you can think of increased heart size from a cardiac arrhythmia arrhythmia, which this is intrinsic abnormalities, cardiomyopathy or failure.

Sometimes you can have both.

So you could have cardiac failure with an arrhythmia, which is what we have in this case.

So this is fetal tachycardia.

I'm gonna come back to this slide later.

You can even see here there's a little bit of failure with a small uh, pleural effusion already.

Now let's look at this heart.

So this is a four chamber view of the heart.

This is some fetal ascites.

Remember I told you about these rules of three rules of three go in here six times.

So we almost have a rule of six.

So if you look here, we know that that heart is too small compared to the thorax.

So what is the abnormality?

Is it sequestration C-P-A-M-C cam chaos?

Exactly what is happening here.

And in this situation there's congenital high airway obstruction.

So we look at the heart, all this was lung that was overexpanded in this case.

And if you look here you can see the over expansion of the lung.

By this time there was ascites, this is high airway obstruction or tracheal bronchial atresia.

So the trachea and the bronchus or dilated and fluid filled.

Size of the Ventricles

Next we're gonna look at size of the ventricles and in particular gonna look at uh uh, the size between the right and the left ventricle.

So is it a right sided abnormality, a left sided abnormality?

In general, the ratio between the right and the left on a good four chamber view of the heart should be about one to one.

However we look at this case left ventricle here, right ventricle here marked discrepancy in size and you can also see very small VSD.

And if we do color flow on here, you can see the VSD, but you can see the marked discrepancy in size and you see no flow across the tricuspid valve.

We put this into motion with real time.

You see nice motion here in the mitral valve but you see no motion at all within the tricuspid valve in this case of tricuspid atresia with a DSD on a on the other hand we have in this case hypoplastic left heart where the left ventricle in one case is much smaller and in this case in real time, left ventricle is much smaller than the right ventricle.

These cases we must recognize 'cause their hypoplasia not only the left ventricle but the left atrium and the aortic outflow tract we're to next look at the ventricles in terms of the thickness of the ventricle.

Thickness of the Ventricles

So take this quick case.

So this would be question three, what is a particular diagnosis In this case we have an area of increased echogenicity within the left ventricle and we're gonna go from there.

Is this a case of tumor thrombus, endocardial fibroblasts, exactly what is occurring in this case.

If we look here, all these cases I'm gonna show you are gonna be cardiac rhabdo myoma.

So this is a huge case of a cardiac rhabdo myoma almost as large as the heart itself.

Cardiac tumors also cause endocardial fibro elastosis because there's usually some obstruction to outflow by that tumor.

So these two can occur together as in this case.

So multiple left-sided cardiac tumors, rhabdo myomas, but there's endocardial fibro elastosis as well shown by this very thickened wall of the left ventricle.

Now we're gonna look at thin ventricles as well.

So we're gonna take a a look at uh, that as our next case.

And in this case here you see a four chamber view of the heart.

You see a very thin ventricle here.

And in fact this is the ventricle in which there's an outpouching, there's pericardial fluid around there.

We're gonna look and with color flow you can see in fact flow out to this extra structure or a thin ventricle.

And this is a ventricular aneurysm.

So thickness within the ventricles, thinness within the ventricular wall, in this case a ventricular aneurysm.

Septum Integrity

Finally the septum on a four chamber.

It's probably one of the hardest things to do because asds VSDs often occur in a number of different uh, places.

We think of these occurring only maybe in the peri membranous portion, but in fact they can occur in the muscular portion or the outlet portion of the uh, of the uh, VSD.

How do these look?

They're very hard to pick up and in most series these are the most common abnormalities missed on a four chamber view of the heart.

Have a little T appearance or a light bulb or a flashlight right at the tip of the VSD or they appear very round in this case.

You can sort of see here the edges are a little rounded off and we can go ahead and do color flow to substantiate this color is very, very important in these cases to substantiate that you do in fact have a very small VSD in this case.

The other thing you have to look at for larger VSDs, I have seen a number of these myths, but you look at this case and you see how the tricuspid valve is inserted closer to the apex than is the mitral valve In this case, on this case over here you can see the tricuspid and mitral valve are inserted at approximately the same level.

They almost make a T but you would almost pass this case, you would say yep, that looks pretty normal to me.

But in fact when you look at it between systole and diastole, you see there's a very large defect here that you would miss if you had a single view static image of the heart.

So it's very important to get real time and do a sweep in different views including A-L-V-O-T view to look for uh, any type of a ventricular receptor septal defect.

This was also associated with trisomy 21.

Also, whenever you have any endocardial cushion defect, you have to look for other abnormalities or if you have another abnormality such as in this case where you have a congenital diaphragmatic hernia, also look carefully at the heart.

'cause if you see one abnormality, there is often another abnormality.

So really the toughest job is for those who ever have to perform that screening exam.

It's much easier for somebody like me who has to do a level two because already I know somebody has seen something and I'm gonna take a second look at that.

Outflow Tracts and Guidelines

The other thing that we have to do now, if we look at what is sort of a recommendation is a guideline is to look at the left ventricular and right ventricular outflow tracts.

And that just came out in the guidelines from the A IUM.

Many of these abnormalities may have a nor normal four chamber or they may not.

So some of these like tetrology of fallot double outlet or the right ventricle certainly will have A VSD transposition.

Sometimes some of these can be picked up such as a common arterial trunk.

They almost always have A VSD.

So some of these can be picked up on a four chamber view of the heart where you see this trunk of arteriosis or this common trunk with a very large VSD in this case.

But if they don't, we really have to do good outflow tracts and the best is try to get that ventricular septum uh, perpendicular to the ultrasound beam.

So we're interrogating it as in this position.

Once we have that, we're gonna look for the left ventricular outflow tract and the right ventricular outflow tract to crisscross.

You really have to see this though in real time, such as in this example where you have the RVOT and the LVOT, the cross one another.

You see this perfectly in this example where you just take the transducer back and forth and this is common that everybody knows basically how to do this.

Now this is a recommendation on examination of the second trimester fetus.

Take this example in which only static images are obtained.

There was a normal four chamber.

L-V-O-T-R-V-O-T doesn't look too bad in reality.

So is this in fact normal or is something going on here?

And in fact, if we look at this, you really have to look in real time at this case because there's almost parallel aorta and pulmonary artery and this is a case of transposition.

So you have to look for that relationship in real time.

They should cross.

If they don't cross, you have parallel vessels.

This could be an indication of transposition in this case.

Here you see one other thing that I'll point out, any tube or structure coming out of the left ventricle that bifurcates early with one of the tubes going over to the left lung, you know is really the pulmonary artery.

So you see it here, you see it here and we call this in a publication.

We had a baby's bird beak.

So you can sort of see are an imaginary baby bird here with their beak.

And that's part of coming out here.

The pulmonary artery from the left ventricle going over here to the lung.

And you can see this very nicely in real time here coming out of the left ventricle, you see this tube which bifurcates one portion going over here and these two structures never really cross one another.

They sort of are parallel to one.

Another problem is when that eex is up, it's somewhat difficult to get these two vessels to cross one another.

And once you do, you have to show everything in real time.

So apex up, we get the LVOT, we think we get the RVOT.

But if you see this, you really have to identify that what you think is a pulmonary artery which bifurcates.

So in this case you see the LVOT very nicely, you see the RVOT.

But it'd be nice to see these crisscross which we don't have or for this to bifurcate as a pulmonary artery to be absolutely sure that we don't have transposition.

Five-Chamber and Short-Axis Views

So what has been proposed in 2001 and we've been using it uh, since 2005 for nearly 10 years is doing five chamber view of the heart or five short axis view of the heart.

First one is just to establish sinus.

The next one is to do a four chamber.

Then we do three or four views above that, but they're all real time suites.

So if we look here, we see a normal four chamber, that would be our second view, we actually see a five chamber.

And in that we're gonna see the right ventricle outflow tract and the left ventricle outflow tract to cross.

We go up one and that thing from the right is gonna come over to the left.

The aorta is underneath there, it's the midline and this is the superior vena cva.

And this is what it looks like on a higher view.

And there's one other higher view that I'll show you of pulmonary artery aorta and SVC.

Why do we do this?

Well, we wanna see the crisscross relationship to make sure we don't have transposition, we don't have double outlet.

Well look at the size of those vessels.

So if you have a hypoplastic left heart, you're gonna have a small aorta, you're gonna look at the number of vessels, et cetera, then you're gonna look at arrangement of the vessels alignment, et cetera, et cetera.

And then in color flow you can look at the pattern of flow.

Normal relationship should be this crisscross.

We see this very nicely in this example here, which there's a nice crisscross the RVOT crosses.

This is the normal real time image we'd get.

You can see the LVOT crosses.

However, we now do the three vessel view and if we look here, RVOT comes over to the left side here.

That's the pulmonary artery theorize.

Underneath that goes centrally here.

And over here we have the SVC that always comes out of the right atrium.

So you see these three vessels lined up very nicely.

Now if the apex is up as in this case, you're gonna see very nicely the RVOT coming over here to the left side, the aorta coming from the left ventricle to the midline.

And if you look closely here, you can actually see underneath here and I'll show you another example where the pulmonary artery bifurcates and coming off here goes over to the left lung and a power.

I'm gonna show you one other view where the two vessels come together, almost NAV.

So again, pulmonary artery aorta and SVC.

I'm gonna show you two examples here and this one RVOT coming over and you can see the pulmonary artery.

Just stop for a moment.

You see the pulmonary artery, then it comes down all the way to the ductus in this view where they come together little off axis here, but that does show you the left pulmonary artery again coming out of the uh, right ventricle in this view.

This is the top view and you can see these two vessels come together as they join the ductus here.

So you see both R-V-O-T-L-V-O-T coming together.

They almost form a V as they come together in this most cephalad view.

Abnormal Findings in Outflow Tracts

Well, what are abnormal things?

We may see, I've just listed a couple here where there's a discrepancy in size, the vessels are parallel.

We see two vessels, four vessels, all different combinations we could have.

First case, I'm just gonna show you the aorta larger than the pulmonary artery.

So we look here, normal relationship, abnormal relationship where the pulmonary artery is smaller than the aorta.

So we know the pulmonary artery is either small or the A aorta is large or a combination they thereof.

And this is tetrology of fallo where we get, uh, normally small pulmonary artery.

There's an overriding aorta.

This is what the normal should look like.

This is what we imagine tetrology of fallo should look like.

And our imagination.

We have the actual image with the pulmonary artery here, the aorta.

And you note the marked discrepancy in the two.

Next aorta is smaller than the pulmonary artery and this is usually hypoplasia of the left ventricle to some degree.

So you look here, double outlet of the right ventricle with aortic atresia.

You see the aorta here, but you see marked discrepancy between the size of the pulmonary artery and the aorta.

And this is double outlet with aortic atresia.

I'm gonna show you an abnormal, another sort of unusual case here, a right outflow tract abnormality here where the uh, pulmonary artery is larger than the uh, aorta.

This first of all was a complex anomaly.

The first thing that was recognized was a question of a cleft lip or palate.

Then you look here, this wasn't recognized in the first go round.

So in 27 weeks this was actually missed pulmonary artery aorta SVC.

But look at that.

There's marked discrepancy in size.

Here was the, uh, outflow tracts in these views and you can see now that you can see this.

So there is the normal outflow tract views we obtained with the pulmonary artery increased in size as compared to the aorta in this case of pulmonic stenosis.

You can then at uh, 30 some weeks I went and re-looked at and this was a large cleft lip plus palate.

The tongue right here.

And you can now see in a normal conventional outflow tract views, LVOT looks okay, but you look at that RVOT, the pulmonary artery is increased in size and then you look at the three vessel views.

So you come from here, see the pulmonary artery is markedly discrepant in size compared to the aorta.

It's much larger.

Actually compresses the aorta a little bit.

And in this case of pulmonic stenosis, we see that the pulmonary artery is much larger than the aorta and actually compresses some of the LVOT as well.

Finally, vessels can be parallel, as we all know, either double outlet or the right ventricle or transposition.

So this is just a case of transposition where the vessels never are identified to crisscross at all.

Then finally, we can have two vessels, four vessels, all different sort of combinations here.

So if you look here, you see the pulmonary artery, you see the SVC, you don't know that's the SVC, but I'll show you it is, but we don't see the aorta.

So it's severe hypoplastic left heart.

And you look here, this is gonna be the whole aorta here.

Very, very small.

So hypoplasia of the left ventricle, you'll look here, see the SVC, you see the pulmonary artery, but you should see in between those and maybe there's just a little dot of the uh, aorta there.

But basically it's gone.

It's virtually a, uh, two vessel, three vessel view.

So there's absent four vessels you can see.

And usually that's with some complex anomaly including duplicated SVC.

And in this case there was duplicated. SVC.

You see this, but there's other abnormalities of the heart.

So you can look at all these.

Is the aorta bigger than the pulmonary artery?

Is the aorta smaller, the pulmonary artery bigger?

Are the vessels parallel?

And these three vessel views, are there two vessels?

Are there four vessels?

Exactly What's happening?

Recommendations for Screening Exams

So really if you look at the hardest job in performing a level one is doing a level one exam, because we have to then at that time say, yep, this heart is okay, I'm gonna pass it, I'm gonna go down, I'm gonna pass this thing, it's fine, or it's no good.

And really we have to look first at our starting point with that PASS.

So you have to look at the position, the axi, you know, really in terms of, uh, the size of the ventricle.

Then you're gonna have to look at the septum in tac.

You have to get that passed.

You have to make sure you see the four chambers.

And then after you understand those four chambers, you can take the next set step.

If that septum is perpendicular to the ultrasound beam, it's very easy to see the outflow track crisscross.

If it's parallel, you have to check the outflow tracks very carefully.

And you should try this three vessel view in real time.

If you're doing these, you have any questions, press the help button, ask for somebody else's help.

So rescan later, maybe at the same setting, go into the other room, go do something else, come back, reschedule the patient a week from now.

Don't let it go.

If you really can't see these, call a friend, call another sonographer, call another somebody into the room, re-scan at a later date or ask for a fetal echo.

Thank you very much for your uh, time and I hope you enjoyed this presentation.

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