What’s Important About the Fetal Heart? - SD

Introduction

My name is Dr. Wesley Lee from the Division of Fetal Imaging at William Beaumont Hospital in Royal Oak, Michigan.

Today I will be talking about what's important about the fetal heart.

Congenital heart disease remains to be a leading cause of death to infants because of birth defects.

And today, we will talk about the importance of the prenatal diagnosis of these problems during pregnancy.

Educational Objectives

In terms of educational objectives, I would like you to understand the rationale for prenatal cardiac screening, and to list the main components of a basic and extended basic fetal cardiac examination.

And then, to identify common fetal heart anomalies by prenatal ultrasound.

Why Perform Fetal Cardiac Screening?

One of the first questions we should ask is, why do it?

We do know that the heart is the window to the rest of the fetus, and this can be a possible avenue for detecting possible associated abnormalities.

This information is also important for counseling our patients regarding the genetics and patient prognosis.

And some patients will opt for pregnancy determination.

This information is also important for antepartum testing and to help to guide where and when to deliver.

And elective selected problems also offer the opportunity for fetal therapy when available.

Congenital heart disease remains to be a leading cause of infant mortality in the United States.

And heart disease is a major portion of this morbidity and mortality.

Challenges in Fetal Cardiac Ultrasound

But let's ask, why is fetal cardiac ultrasound challenging?

We're talking about a very narrow window development, ranging from a very small beating heart at four weeks conceptual age to roughly eight weeks.

And for one thing, the fetal heart is quite small when compared to a United States nickel.

You can see on the left that if you look at Jefferson's nose, you can see that the ventricular septal defect in this area of a 20 week heart is about the same size as Jefferson's nose or chin.

So, if the fetal heart is moving very fast at roughly 100 to 140 beats per minute, roughly, and if you throw in other factors such as the maternal body habitus, or fetal position, all those factors make the examination of the fetal heart quite challenging.

Also, the fetal heart development is complex.

There was a time when I was using these clay models, trying to develop sections, cross-sectional sections of the fetal heart to teach cross-sectional anatomy for sonographers and sonologists, trying to understand the fetal heart.

And but then as time went on, and we also tried to use computer animation techniques to show how the heart develops between 21 and 35 days conceptual age.

This is an example of a fetal heart developing.

We start off with the embryonic disc, and we have a condensation of mesenchymal cells on the cranial end of the embryonic disc, showing these two cardiogenic tubes fused together.

And then the tube bends and twists in a certain way within a confined space to form the anterior right ventricular outflow tract and the most posterior ventricular system and atria.

But there have been a lot of other scientific studies, for instance, in the chick embryo, showing how this process develops.

And this is an example of dilution or dye marking techniques, and scanning electron microscopy, which shows the two tubes fusing and twisting into the ventricle and future portions of the heart.

But subsequent studies have shown that the basic concept that I just showed you is not quite all that happens.

The straight heart tube does not consist of all future regions of the mature heart and the right side of the right bend of the heart or looping.

It's not simply a bending of the straight heart tube, but actually results from three distinct events.

The dextral looping does not bring the subdivisions of the heart tube and great vessels together, but this is achieved from developmental changes after this looping occurs.

And there are also some advanced techniques, that where they can actually mark the cells and show where the various cells move and migrate to, to refine our concept of heart development.

But the basic overall concept that I'm trying to explain is simply that the development of the fetal heart is a complex process.

We're constantly learning about more things about how the anatomy results from a very early stage.

And then we're trying to understand the best ways to diagnose these abnormalities prior to delivery.

Detection Rates of Heart Abnormalities

How well can we detect heart abnormalities?

There have been many studies looking at cardiac screening with a four chamber view.

And some of the very earliest studies were performed by Dr. Lindsey Allen and Gurley Charlin in the United Kingdom, which showed pick up rate about 7% of the abnormalities found by the 14 review.

Dr. Josh Copel at Yale reported a 92% pickup.

But there's been a whole range of sensitivities ranging as low as 5% to 92%.

And personally, I think that the reason why this wide range occurs was related to the degree of education.

And in addition to the advances in imaging technology.

As if you take an example of the RADIUS trial, this is the largest randomized controlled trial of universal screening of all pregnancies by ultrasound.

You can see that this was largely a study that was performed mainly in the Midwest and plus East Coast, involving technicians, sonographers, radiologists, and OBGYNs.

And this is a study where they the design took approximately 16,000 women and split them into any ones that had ultrasounds due to indications only, as opposed to universally screening them from 15 to 22 weeks, and again, at 31 to 35 weeks.

The perinatal outcome, maternal morbidity and diagnostic accuracy were examined regarding the RADIUS trial and cardiac screening.

Only 17% of the abnormalities were detected before 24 weeks, and only 13% of the cardiac malformations were detected prenatally.

A more recent study that was reported in Norway looked at the prenatal detection of heart defects in an unselected population of approximately 30,000 fetuses.

And their study involved cardiac screening at 18 completed weeks between 1991 and 2001, beginning in 1995.

The second exam was offered if the initial screening did not provide satisfactory views at 20 weeks, approximately 57% of the major congenital heart disease cases were detected, and 27% were alive after two years.

They also looked at the examiner's ultrasound experience on the detection of these defects at the second trimester examination.

And they had sonographers and midwives that were performing the cardiac screenings stratified by experience, ranging from three months to seven years.

They arbitrarily took two classifications, those individuals having 200 to 2000 routine heart examinations.

And the more experienced ones having greater than 2000 routine heart exams.

And they compared the detection rates between the two groups.

Their results indicate that training and experience has a significant impact on fetal cardiac screening for major congenital heart disease.

So they also documented a learning curve for the basic and extended basic cardiac screening examination.

We can learn a lot about the natural history of these congenital heart defects from the work of Dr. Simcha from Israel, where they took 22,000 women who underwent cardiac screening.

If you look at the slide, you can see that the groups were broken down by the ones that received early scans and then mid trimester scans, and then third trimester scans and postnatal.

So there was one group, group A, that began their scans at 13 to 16 weeks transvaginally.

And this was followed by the routine 20 to 22 week abdominal scan, third trimester scan, and postnatal scan.

And then there's a group B that was more traditionally followed, beginning at the 20 to 22 weeks abdominal scan.

In that study, they found 168 babies with heart disease.

And you can see the different groups, the pink being the group A, the ones that were followed ever since the early pregnancy time period.

And you can see that even at 13 to 16 weeks, that 64% of the congenital heart disease cases were detected this early on.

But as we advanced through pregnancy, the pickup rates were about the same at 20, 22 weeks during third trimester and also postnatally.

But the main point of this slide is simply to show that we can see a lot of detail in the fetal heart, even before 18 weeks.

And about over half of the congenital heart disease cases can be detected in this early stage of approximately 13 to 16 weeks.

In their study, they had a lot of different abnormalities that they can see ranging from aortic stenosis to VSDs, to transposition to double outlet right ventricle, and these cases were variably picked up in both groups as seen in this slide.

And because these were longitudinal studies, they were able to show that some cases were picked up involving aortic stenosis, tetralogy of Fallot and cardiac rhabdomyoma during the third trimester.

And you can see that throughout pregnancy, miscellaneous lesions were picked up, which emphasized the concept that when we examine our hearts, especially at the screening examination, that this is simply a snapshot of what's going on that time.

And whether you look at the patient later that day or later that week, or multiple times, the chances of picking up a abnormality are higher as time goes on.

And if you look from different perspectives, if you look at the cardiac abnormalities detected after delivery, you can see that ventricular septal defects were by and large, the largest group, 17 detected there, and seven were relatively large.

But other things involving the aortic outflow tract, the pulmonary stenosis, atrial septal defect, coarctation, and so forth were also missed.

So they concluded that the evolution and or late appearance of some heart defects accounted for a majority of missed cases.

And although most fetal cardiac anomalies are detectable early in gestation, some may involve evolving in utero at different stages of pregnancy.

Timing of Cardiac Screening

So, from a practical standpoint, we might ask when should cardiac screening occur?

And it really should be a balance or a yin and yang between early enough to detect major cardiac abnormalities that allow parents to consider options, but late enough not to miss late developing lesions.

Dr. Lindsey Allan has written an opinion talking about recommending that low risk patients should be screened at roughly 20 weeks.

And that one option for high-risk patients would be to perform a 12 to 14 week early echo initially, and then to do a repeat scan at around 20 weeks.

This is just an example at a 13 and a half week scan of the detail that you can see.

In this case. You see that both ventricles are nicely formed, and the heart beating, the cardiac axis and position look good.

You can see four chambers develop very nicely, and you can get a suggestion of two outflow tracts, the aorta coming from the left ventricle, if I can get this here right like this.

And then the aorta coming, the pulmonary artery came from the right ventricle.

You get the impression that the great vessels do cross each other and are approximately the same size.

But also even at this early stage, you can appreciate that the atrioventricular valves appear offset, and you can see two separate AV valves.

So there's quite a bit of information even at this early stage.

This is a 14 week scan, and again, we can see a lot of nice anatomy.

It's not the same thing as a 19 week scan, of course, but I think that major abnormalities such as hypoplastic left heart or atrioventricular septal defect could be detected from this type of presentation.

Guidelines for Basic Fetal Cardiac Examination

In 1998, the American Institute of Ultrasound in Medicine had a task force that developed the guidelines that are often quoted for the performance of the basic fetal cardiac ultrasound examination.

And these guidelines were also adopted and revised by the International Society of Ultrasound in Obstetrics and Gynecology.

This particular document can be found in this journal in January, 2006 issue, and also materials and multimedia versions of the guidelines can also be found on the AIUM website.

If you look at the technique for scanning the cardiac views, because of the increased size of the liver, the heart is really pushed up.

And so you can actually obtain the four chamber view of the heart from a subcostal view.

If you look at the diagram on the right, you can see that the four chamber view is this plane right here.

It's marked by the red plane on the left.

And just by swinging the transducer towards the fetal head in a small arc, will provide you the left ventricular outflow tract.

It's marked in green, and the most anterior right ventricular outflow tract of the pulmonary artery, most anteriorly, as shown in yellow.

Four-Chamber View Criteria

One of the most common misnomers or misconceptions of the four chamber view is that we're talking just about a four chamber view.

So many people think that we're just talking about counting four chambers, but this is really incorrect.

The four chamber view of the heart is based on a set of specific diagnostic criteria that include that the heart rate is between 100 and roughly approximately 160 beats per minute, that the rate and rhythm are normal.

The axis position situs of the heart's normal, making sure there's no fusions or hypertrophy, that the intact ventricular septum is present with the crux where the atrioventricular valves are offset, and that the symmetrical heart chambers are normally developed.

Cardiac Axis and Position

So let's talk about some of the components of the basic cardiac screening examination, when we talk about the cardiac axis and position, then the cardiac axis is measured by developing a line from the spine to the sternum.

And by taking a line from the base of the heart to the apex of the heart, we can measure the angle called the cardiac axis.

And normally this axis lies at around 45 plus or minus 20 degrees.

Now, there are some patients that are walking down the street that with a cardiac axis that's abnormal, but otherwise they're doing fine.

And so this can be a variation of normal, but when we do find an abnormal axis, it is an indication for a detailed scan.

And if the heart is pointing straight, then this is called mesocardia.

And if the heart is pointing towards the right, that's called dextrocardia.

And if you look at the base of the heart where the atrial septum meets the base of the heart, we can call this the P point.

And in most cases, in about 96% of the cases, the P point occurs in these four squares marked in a purple color.

And in some cases where the heart is outside of this range.

So the heart is pushed way over to the right, that's called dextroposition.

And in that case, this can be caused by a mass occupying lesion, such as a diaphragmatic hernia on the left, pushing heart to the right or the presence of a tumor such as a dermoid or a cystic adenomatoid malformation.

So the point is, when you see dextroposition, you should look for a chest mass.

In this particular clip, you can see that the heart is enlarged, and then it's rotated more towards the left.

This is a case where we should really be vigilant and not miss these type of cases.

But you can see that this is the left side, and this is the right side.

The heart's pushed way over to the right by this area over here, which represents the presence of intrathoracic bowel in the left chest, pushing the heart to the right.

So this is a case of a diaphragmatic hernia.

At William Beaumont Hospital we took approximately 42,000 fetuses and screened the babies, the fetuses with cardiac axis screening.

And we found 34 fetuses with left axis cardiac deviation.

26 fetuses were abnormal, and eight were normal.

And of the abnormal fetuses, 21 had abnormal hearts, and five fetuses had extracardiac abnormalities.

Detailed Four-Chamber View Assessment

Don't remember if that or not.

So if you look at the four chamber view of the heart, again, it's not just four chambers of 1, 2, 3, 4, but we're talking about a list of diagnostic criteria that we discussed before, that the ventricles are nicely developed.

The atria are nicely developed.

There's no disproportion, that there's no evidence of cardiac hypertrophy or a fusion.

And now, there's another aspect of this that I'd like to point out.

And you can see how the septal insertion of the tricuspid valve right here, it's a little more apical than the mitral valve insertion.

This is called the offset valves of the crux.

And this is a normal feature that should always be seen because sometimes, especially in the case of a atrioventricular septal defect, the valve can just be only one AV valve may be there forming a straight line going across this area.

Extended Basic Cardiac Examination

Now there's also the concept of the extended basic cardiac examination.

So when technically feasible, this extended basic cardiac examination can be should be performed to look at the left and right ventricular outflow tracts.

The formation of the cardiac outflow tracts is quite complex, and it depends upon the development of this spiral septum, which separates the primitive truncus into the anterior right ventricular outflow tract, and the more posterior left ventricular outflow tract.

But simply by angling the transducer towards the fetal head, you can see one outflow tract, the left ventricular outflow tract coming from the left ventricle.

And in this view, the ventricular septum should be contiguous with the more anterior wall of the aorta, because this is an area where ventricular septal defects can be seen, where it may not be seen in a four chamber view.

And by swinging the scanning plane up more most anteriorly, you can get the right ventricular outflow tract too.

But this is just an example of the left ventricular outflow tract, and you can see the aorta coming out from the left side.

And then by looking at the right ventricular outflow tract, sometimes you can see the bifurcation of the vessel.

That's ideal, but you don't always see that.

And then you can see in this clip, you can see the right ventricular outflow tract here, and you can see the left ventricular outflow tract here.

And really from the standpoint of screening, the main goal is simply just to see that there are two outflow tracts about approximately the same size, that crisscross each other from respective ventricles.

If you've done that, then you've done your job for screening for abnormalities of the great vessels.

The extended basic cardiac examination provides more information about a wide range of conal truncal abnormalities that include transposition of the great arteries, tetralogy of Fallot, double outlet right ventricle, and may give us other clues about valve stenosis or coarctation.

But studies have shown, among others, these two studies have shown that with the basic cardiac examination of the four chamber view, you can detect approximately 50% of the cases of heart disease.

And by adding the outflow tract examination using the extended basic examination, this pickup rate or sensitivity increases to approximately 80%.

One might ask how often we can visualize the outflow tracts and that at William Beaumont Hospital.

We examined 19,000 patients looking at the normal four chamber view, and we found that 7% of these fetuses had either the pulmonary artery or aorta, or both, poorly visualized.

Three-Vessel View

There's also another type of view called the three vessel view that's been reported in the literature.

And this was originally reported by Dr. Yagel in 1997, showing the pulmonary artery, the aorta, and the superior vena cava.

And you can see that in this case that the pulmonary artery or the right ventricular outflow tract connects to through the ductus, to the descending aorta.

Dr. Yagel described 28 to 29 fetuses that demonstrated an abnormal three vessel view on the basis of criteria such as vessel size, alignment, arrangement, and vessel number.

Now, these are some examples from his paper that shows examples of Ebstein's anomaly, aortic stenosis dilatation, and tetralogy of Fallot.

Now, the purpose of these pictures are not to confuse you, but simply to make you realize that when that the normal arrangement of the vessels are that the pulmonary arteries the largest, followed by the next largest, the aorta and the smallest, the superior vena cava.

And they usually form a line.

If you don't see that pattern, then these patients should be referred for a more detailed scan of the heart.

There are other groups in around the world, from Israel and Italy and others that have also described the three vessel view.

And they also described something called the three vessel and trachea view for detecting these type of abnormalities.

Dr. Yagel also described another way to look at the fetal heart by four short axis views.

So you can see the lowest one over here, the most inferior, showing the stomach and the liver.

So you can check situs.

Then you have the four chamber view, the LVOT, the RVOT, and the three vessel trachea view.

So by now, all these the standard views should become familiar to you.

So for the cardiac views, we should think about the four chamber view and the left ventricular outflow tract and the right ventricular outflow tract.

Detecting Ductal-Dependent Lesions

Now, one of the main reasons why we even do this is because we're trying to detect which fetuses are at risk for having a ductal dependent lesion.

Because shortly after birth, the ductus, the ductus arteriosus begins to close.

Dr. Vial from Chile showed a very nice demonstration of when you apply Doppler ultrasound color Doppler to the great vessels, they should all be showing forward flow through both outflow tracts.

But if you see something like this where flow's going out and flow's going in on respective great vessels, then you should be suspicious that there might be some retrograde flow.

And this is suspicious for ductal dependent lesions.

Indications for Detailed Fetal Echocardiography

So far we've been talking about screening of the heart, and there are selective indications for a detailed study of the heart that include an abnormal screening examination, or a family history of a first degree relative for the heart disease, and patients with selected drug exposures to, for instance, lithium and maternal diabetes.

But this becomes a more difficult question about what actually constitutes a fetal echo.

Is it more than just a four chamber view and outflow tracts?

And for that question, I would refer to you to a ACOG consensus statement that was published in 2008, as you see here.

Common Fetal Heart Anomalies

So with that background, let's talk about some of the common cardiac problems that we can see.

Ventricular Septal Defect (VSD)

For instance, the ventricular septal defect, which includes a defect that involving the inlet or outlet or the perimembranous areas of the ventricular septum.

The defect can also occur in the muscular portion as well.

These small VSDs can be very easy to miss.

And you can see that this little break right here can only was probably only apparent from the left ventricular outflow tract view.

And this is a muscular VSD over here, so they can be very small and they can actually close on their own as well.

But the key points for detecting a VSD is to optimize your technique and making sure that the focus gain and magnification are appropriate.

In fact, one of the basic steps that are often forgotten is to magnify the area of interest, so that we can actually see what we're trying to find and to make use of the digital cine loop sometimes going frame by frame.

And there's something called gray scale priority in many of the modern systems that allow you to balance the gray scale to the color presentation by the computer.

And this is important for trying to see these small holes and to remember that the ventricular septum is a three dimensional structure.

So it's important to look at the entire septum.

And if use a suspected possible VSD to verify from other views, power Doppler can also be used to detect these ventricular septal defects.

And this is an example of how you can balance the color and the power Doppler.

And you can see the gray scale and the anatomy very well.

Atrioventricular Septal Defect (AVSD)

Atrioventricular septal defect occurs when the middle of the heart is essentially not formed correctly.

So you just, instead of a separate atrioventricular valves that is the mitral tricuspid valves, you have a common atrioventricular valve as seen here.

And you have a presence of a atrial septal defect and a ventricular septal defect.

And in the complete form of the AVSD, you have one AV valve.

This is also called or known as endocardial cushion defect or an AV canal.

And in this case, you can see that the usual offsetting of the AV valves is not there.

You see one straight line going across instead of the offset valves that usually see, and this is pathognomonic of a atrioventricular septal defect.

Even at 15 weeks, you can see a atrioventricular septal defect.

You can see that there's these lines, this line going across when the valves close, and you can see a suggestion of the AVSD and ASD.

Once you recognize the pattern, it becomes pretty easy to suspect.

This is another example with the heart pointing downwards.

This is not the best view.

In fact, the four chamber view is best visualized when the apex the heart.

It's more pointing at the 10 o'clock to two o'clock position.

But despite this, despite the prone position in the fetus, you can still appreciate that the AV valves are in a linear fashion.

And you can see the VSD here and the ASD here, that suggests the AVSD.

And here's just another example of that line going across with the ASD and the VSD for this abnormality.

AVSDs are commonly associated with trisomy 21, and the possibility of heterotaxy syndrome, heart block, and congestive failure should be considered, and rarely AVSDs are associated with tetralogy of Fallot.

Hypoplastic Left Heart Syndrome

The hypoplastic left heart syndrome is something we should never miss.

And we can see from this four chamber view that there's a marked disproportion between the right and left ventricle with the left ventricle sometimes being very diminutive, almost like a sliver.

And one of the clues to this is also that the flow across the foramen ovale, instead of right to left, it goes from left to right as shown by the arrow.

If you look at this example, you'll see how color Doppler ultrasound can help you to determine the flow across the foramen ovale.

And the most ventricle is right.

So this is the right side, and this is the left side.

And you can see that the flow is going from the left to the right side because the flow is going towards the transducer, which is orange, and this is reversed from the usual case.

So this is indicative of or consistent with hypoplastic left heart syndrome.

Dr. Wayne Cohen at the Brigham Women's Hospital has reported some improved surgical outcomes after the fetal diagnosis of hypoplastic left heart syndrome.

And they're able to show that when this problem is diagnosed prenatally, that these fetuses are less likely to be sick at presentation because of less acidosis, less decreased needs, decreased need for inotropes and bicarbonate, and less severe right ventricular function.

So they said that prenatal diagnosis of hypoplastic left heart syndrome was associated with improved preoperative clinical status and with improved survival at the first stage palliation in comparison to controls.

Conotruncal Abnormalities

Conotruncal abnormalities of the great vessels include a wide range of problems including truncus arteriosus, double outlet right ventricle, tetralogy of Fallot, transposition of the great arteries.

And versus by looking at this type of diagram, you can see the normal situation where the pulmonary artery is anterior and the aorta is posterior.

And then you have situation of double outlet right ventricle, and then you have D-transposition where the aorta becomes anterior and the pulmonary artery posterior.

You can have a persistent truncus where the truncus did not separate into the two vessels, the aorta and pulmonary artery.

Or you can have a mirror image of the D-transposition, you can have L-transposition.

But the point is that these conotruncal abnormalities result from problems with the way the spiral septum separates the primitive truncus, as I showed you in the computer animation before.

You can even have situs inversus as well as shown by this arrangement here at the very bottom of the diagram.

Tetralogy of Fallot

Tetralogy of Fallot is an example of the conotruncal abnormalities.

It may present with a VSD and overriding aorta, but it's important for us to watch for worsening RV obstruction and pulmonary stenosis.

The prognosis is generally good in the absence of other abnormalities, but prostaglandin infusion may be important to maintain ductal dependency.

So if you look at this diagram, you can see that you have the overriding aorta overriding of VSD, and there's a small pulmonary artery.

And in the adults, you can see right ventricular hypertrophy, which is not always apparent.

In fact, it's almost not recognized as a rule in fetuses.

So generally speaking, some of the things you can only that you see during fetal life is simply just a VSD and an overriding aorta.

And if you see something like that, then it's important for you to see the patient later to make sure there's no evidence of pulmonary artery stenosis.

And if you look at this diagram, you can see how in tetralogy of Fallot you have a relatively large aorta and a relatively small pulmonary artery.

It's important for tetralogy of Fallot to look for a small right ventricular outflow tract.

So you can just barely see a little right ventricular outflow tract here, as opposed to the large aorta over here.

The important thing to know about tetralogy of Fallot is how relatively normal the four chamber view can appear because you're not looking in the right plane.

So if you look on the left, you can see the VSD and the overriding aorta, but you can get some similar planes, but from a four chamber view that appear relatively normal and that this can be missed.

If you look at the high short axis view, you can see the relative disproportion of the dilated aorta and the very small pulmonary artery that bifurcates over here.

That's characteristic of TOF.

Transposition of the Great Arteries

Transposition of the great arteries is a situation where the right ventricle gives rise to the aorta and the left ventricle gives rise to the pulmonary artery.

And the important diagnostic feature of this lesion is that the usual spiral that you see, where you see crisscrossing great vessels crossing over each other is not there.

And instead, you see parallel vessels as you see in this diagram.

So when you see whenever you see parallel vessels coming out of the heart like this, that should raise all sorts of flags that transposition of great arteries might be a very important possibility.

Again, you can see the parallel vessels here and here, and parallel vessels in this view as well.

Whenever we see those parallel vessels, that's an important clue.

You can even use color or power Doppler to show these vessels as well.

Dr. Bonnet did a very important study showing that he compared 68 babies or fetuses that had a prenatal diagnosis of transposition and as opposed to a larger group of 250 babies that had only the postnatal diagnosis.

And basically speaking, if you look at the outcome measures such as the birth admission interval, the need for mechanical ventilation or the instance of acidosis, you'll see that there's a significant difference in that the ones that were discovered prenatally had fewer complications.

But if you look at the pre and postop mortality, you can see 0% for prenatal diagnosis as opposed to six to 8% for infants that had the diagnosis only after delivery.

So their results suggest that when transposition is diagnosed during pregnancy, that delivery should take place in the institution that can provide adequate postnatal care.

Coarctation of the Aorta

One of the last things I wanted to mention was the issue of coarctation.

And I think that traditionally we've relied on looking at disproportion between the chambers or great vessels, and Dr. Lindsey Allan looked at a prospective study of 2000 pregnancies, 24 fetuses presented with dilated right ventricle and pulmonary artery.

In 18 of those fetuses had coarctation or interrupted aorta.

At William Beaumont Hospital we've looked at the normal ranges for ratios between the pulmonary to aortic diameters or the RV to LV diameter ratios.

And we developed these normal ranges and have found this is another way to detect these type abnormalities.

Usually in a normal case, you have pretty much pretty good symmetry between the ventricles as opposed to the case on the right, for instance, where you have discrepancy or asymmetry.

And then looking at the great vessels.

Also, you can see that in the image on the left, you can see that the aorta and pulmonary artery are nicely developed as opposed to disproportion with the relatively large aorta and relatively small PA on the right.

Conclusion

In conclusion, cardiac screening is one of our remaining challenges that we need to refine our skills for the basic cardiac examination that detects approximately 40 to 50% of heart abnormalities.

And if technically feasible, I think it's important to evaluate the outflow tracts as well, that can improve the detection of CHD to about 80%.

But the screening will depend on several factors that include the examiner experience, the type of equipment you're using, as well as the fetal age position, that movement of the fetus.

There is a move, especially in Europe to detect these lesions earlier.

And I think that the evidence shows that we can push the bar or in a sense lowering the gestational age earlier in the 18 weeks to see what we can see on the screening views of the heart.

And I think that if we pay attention to these details, that we can maximize our ability to detect these lesions.

So, as a metaphor, I'd like to leave you with the idea that the fetal heart is a window to the rest of the fetus.

And to remember the basic cardiac examination and if technically feasible the extended basic cardiac examination.

Thank you.