Clinical Presentation of Congenital Heart Disease in the First Week of Life: Murmurs,
by Dr. Michael Freed.
Introduction.
My name is Michael Freed and I'm a Pediatric Cardiologist at Boston Children's Hospital
and at Harvard Medical School.
I want to spend a little time today talking about congenital heart disease in the newborn
period.
If you look at all congenital heart disease, it occurs in about eight out of 1,000 live
births.
And that's fairly constant, regardless of where in the United States or around the world
you look.
The incidence of different diseases may be a little bit different, but the total group
is actually remarkably constant.
If I make a semi-arbitrary definition of severe congenital heart disease-- or critical congenital
heart disease-- a heart disease requiring cardiac catheterization, cardiac surgery,
or dying of your congenital heart disease in the first year of life-- about a quarter
of these children have critical congenital heart disease.
That is about 2.23 per 1,000 births.
This pulls out the children with a small ventricular septal defect, or atrial septal defect, or
mild pulmonary, or aortic stenosis.
These are the kids that are really sick.
If you look at this group-- and I've made the definition the people who come in the
first year of life.
If you look at the group that comes in in the first month of life, about 2/3 of this
group comes in in the first month of life.
And if you look at the group that comes in the first month, about 2/3 of those come in
in the first week.
So coming in in the first year of life is very heavily weighted toward that first week
of life.
In the Regional Infant Cardiac Program, which was an association of the pediatric cardiologists
around the Boston area in New England in the 1960s and 1970s, they collected all the data
on these kids with critical congenital heart disease.
And remember, this was an era where we were doing palliative surgery but not very much
corrective surgery.
So we were doing pulmonary artery bands or shunts but no open-heart surgery correction
of congenital heart disease.
If you look at this group that comes in the first week of life and follow them to their
first birthday, about 43% of them made it.
More than half the children who came in that first week of life actually died of their
congenital heart disease, hence this lecture of heart disease in the first week, following
Sutton's rule.
And for those of you who don't know what Sutton's rule is, it was named after Willie Sutton
who was a bank robber in the 1930s.
And apparently not a very good bank robber.
And the third or fourth time he got arrested, the police said, Willie, why are you robbing
banks?
You don't seem very good at it.
And he said, well, that's where the money is.
So we're going to talk about heart disease in the first week of life because that's really
where the disease is.
Children come in in the first week of life.
They present in one of four ways-- with a heart murmur, with an arrhythmia, congestive
heart failure, or with cyanosis.
Let's start with heart murmurs.
Neonatal Murmurs.
A murmur is just a noise you hear with a stethoscope, and it's caused by turbulence of blood flow
in the heart.
And that turbulence of blood flow in the heart is caused by a pressure drop.
You go from laminar to turbulent flow whenever there's a pressure drop.
So whenever you hear a murmur, it's a sign of a pressure drop somewhere in the heart.
And to get from that pressure drop to a murmur, you go through a variety of steps.
The pressure drop causes the turbulence in the flow, the turbulence in the flow causes
vibration in the blood, which causes a vibration in the wall of the heart, which causes a vibration
in the pericardium, causes a vibration in the subcutaneous tissue, causes a vibration
of the inner chest wall and ribs, subcutaneous tissue, skin, diaphragm of your stethoscope,
column of air, your eardrum, the eardrum goes back and forth setting off an electrical impulse,
that electrical impulse goes to your brain, aha, murmur.
A lot of places to lose information.
And while in physical diagnosis in medical school, they give you a whole variety of things
when trying to characterize them, I found that most of them don't work very well in
the newborn period.
Children's hearts are-- the sounds are transmitted so well over the chest that it's very hard
to localize.
And I think I'm pretty good at telling systolic from diastolic and loud from not loud, but
other than that it's very hard to sort out exactly the quality, timing, pitch, of the
murmur, etc.
So I'm just satisfied with loud or not loud.
Now there are three classifications, three things that can cause heart murmurs in the
newborn period.
One of them is peripheral pulmonary stenosis.
Another is patent ductus arteriosus.
And these are two normal findings.
And then the third is all congenital heart disease.
And I want to tease out these little bit.
Peripheral pulmonary stenosis, as you know, is a murmur that we hear very commonly in
the newborn in the first month of life.
Usually, you hear it in the chest, but you can hear it in the axilla and the back.
[MURMUR SOUND] And this is caused by relatively narrowed vessels in the newborn period.
Blood vessels grow in utero depending upon the amount of blood going through them.
Remember, in utero the organ of oxygen exchange is the placenta, not the lungs.
So, of the blood that the right heart pumps at 50% of combined matricula output goes out
the main pulmonary artery, most of it is diverted down into the descending aorta through the
ductus arteriosis to the placenta.
Only about 10% of combined ventricular output actually goes out to the distal pulmonary
arteries, where it goes out to the lungs and back through the pulmonary veins essentially
unchanged.
So that 10% flow, the blood vessels, the pulmonary arteries, are 10% size blood vessels.
At birth the baby takes a deep breath, the pulmonary resistance drops, the ductus arteriosis
gradually closes, and all of a sudden all that pulmonary artery blood flow goes out
the main pulmonary artery to the distal pulmonary arteries.
And these 10% size vessels all of a sudden are getting 50% of the flow, and you get turbulence
at the branch points which you can hear as peripheral pulmonary stenosis.
[MURMUR SOUND] This is a physiologic murmur.
Over the next few weeks and months, this increased flow increases the wall stress on the vessels,
and the muscle in the pulmonary arterioles gradually regress, so these vessels grow and
get more adapted to the amount of flow going through them and the peripheral pulmonary
stenosis murmur goes away.
Patent ductus arteriosus.
Some of the babies will have a murmur.
If you ask the incidence of patent ductus arteriosus-- if I asked a group of medical
students I'll get 10%, 20%, 25%, but in fact, I think all babies have a murmur of a patent
ductus arteriosus.
This is a normal vessel that's there in utero.
Over the first day or two, this vessel closes.
So you have a situation where you have a high-pressure aorta, a lower pressure pulmonary artery,
a blood vessel connecting the two of them that's starting to get narrow.
Well, you get a pressure drop and you get turbulence, and I think you would get a murmur
in just about every baby.
[MURMUR SOUND] We don't hear it because we don't continuously listen to babies.
We send them out to the mother, they start doing some feeding, the grandparents are holding
them, so there are long periods of time where we don't listen to them.
And I think during those times some of them have murmurs.
Typically I'll get-- when I'm doing consults at the hospital-- I'll get called over to
see a baby at the nursery that the resident has heard a murmur, or the attending physician
has heard a murmur.
They call the cardiology fellow over to listen, and then I come over at the end of the day.
And by the time I get there, half the time it's disappeared.
I think these were just ductuses that were closing.
Diagnosis.
The fact that every baby in the nursery can have a murmur raises a particular question.
There you are in the nursery, and you hear a murmur on a newborn, and you have to make
the decision whether or not it's the 499 out of 500 children who have a PDA-- that's a
normal, physiologic thing that's going to go away-- or that group we talked about, 2
out of 1,000 or 1-in-500 children who have critical congenital heart disease.
So how are we going to decide, with this baby who has a murmur, whether or not he is the
1-in-500 or the 499-in-500?
Well, what we usually get is, we get a series of tests, we usually get an x-ray to look
at the heart size and the pulmonary blood flow.
We get an electrocardiogram, we usually ask for four extremity blood pressures.
We asked for pre- and post-duct saturations.
What we sometimes get is an echocardiogram.
So let's look at these and see how well they work.
Let's look at the x-ray first.
How good is the x-ray in picking out this 1-in-500 from the 499 out of 500 that are
normal?
Well, most studies suggest a sensitivity specificity in the range of 60%, which is not bad, but
I don't think it's good enough to stake a child's life on.
EKG.
Also in the range of 60% or so.
Again, OK, but not terrific.
Four extremity blood pressures.
This is my favorite because I think this-- we always ask them to do this, it's a little
hard to do, the babies are squiggling around.
I think this is useless.
I think this picks up 0% of these kids.
In the first place, we're looking for coarctation of the aorta, and coarctation only occurs
in one in every 10,000 or 12,000 births, so we're going to miss most of these-- most of
the 1-in-500-- anyway.
But even in that group, if the ductus is open, I don't think you're going to have much of
a blood pressure difference anyway.
So even if the baby has critical congenital heart disease, if he doesn't look sick, the
ductus is probably open and you're not going to get any difference in blood pressures.
When we go to the echo-- now here's a test we can all love-- the echo is probably 99+
percent accurate.
This is very effective at picking up heart disease, but not very cost-effective.
And not available to many hospitals where they don't have an echocardiographer right
on call who can look at all this stuff.
So I think it's unnecessary to do this on every baby.
Ductal Dependent Congenital Heart Disease.
Why is this baby, who looks so good at 24 hours of age when he's ready to go home, all
of a sudden crash in 24, 48 hours and look terrible?
I think the issue here is that they have duct dependent heart disease.
They have a disease where, if the ductus arteriosis closes, they crash and get sick.
So let me change the question around a little bit.
Is there a way to sort out ductus dependent congenital heart disease from all of these
other things, from PPS, PDA, and non-critical congenital heart disease?
And I think there is.
And it's based on a peculiarity of duct-dependent circulation.
Duct-dependent heart disease comes in two different flavors.
The first flavor is right-sided disease, for example, tricuspid atresia.
So in tricuspid atresia, the tricuspid valve never forms.
The right ventricle is either very small or nonexistent.
Blood comes back to the body, into the right atrium, can't get through here, goes across
the foramen ovale into the left atrium, left ventricle, out the aorta to the body.
Some of it goes through the ductus arteriosis out to the lungs where it gets oxygenated
and comes back again.
So in utero, this is not a problem.
And after birth, this isn't a problem.
But when the ductus arteriosis starts closing, the blood going out to the lungs is markedly
reduced, less blood is oxygenated, and the oxygen in the system gradually goes down.
Blood going out to the body is quite hypoxemic.
Then the amount of blood going through here diminishes.
The blood going to the lungs to get oxygen is reduced.
And gradually, the arterial saturation will decrease.
There'll be more hypoxemia.
Eventually, as you get the oxygen level low enough, you stop perfusing the distal tissues.
And those cells go from aerobic to anaerobic metabolism.
They go down a pathway that builds up to molecules of lactic acid.
And the children start getting acidotic.
Eventually, they get more and more acidotic, denature their enzymes, and they die.
So these kids are dependent on the ductus arteriosis for their pulmonary blood flow.
And if you look at something-- other right-sided disease instead of tricuspid atresia, you
make a model of pulmonary atresia, sort of the same physiology.
If you have Tetralogy of Fallot, then you shunt at the ventricular level.
But all these kids are dependent on the ductus arteriosis for their pulmonary blood flow.
As opposed to this group.
There is the group with left-sided disease, for example, hypoplastic left heart syndrome.
So these kids-- blood coming back from the body comes back right atrium, right ventricle,
out to the lungs, back again, left atrium, can't get through here, cross the foramen
ovale out this way, and some go through the ductus arteriosis to the ascending and descending
aorta.
So when the ductus starts closing here, these children don't have any difficulty with oxygen
saturation.
They've got plenty of pulmonary blood flow.
But there isn't enough blood getting out to the systemic circulation.
So they start becoming hypotensive.
And again, if they get hypotensive enough, they don't profuse their distal tissues.
They go from aerobic to anaerobic metabolism, build up lactic acid, and get acidotic and
go through that same cycle.
There's a similarity in these two circulations in addition to having the ductus arteriosis
and the foramen ovale.
And what it is, is that in both of these situations, all the blood from the right and left side
of the heart is mixing in one of the chambers.
So in right-sided disease, all the pink blood and blue blood is mixing in the left atrium.
With Tetralogy, it mixes in the ventricle, but it's mixing on one of the sides of the
heart with all right-sided disease.
In left-sided disease, all the blood is also mixing.
Here, it's mixing on the right side of the heart.
So if the pink blood and blue blood are mixing in one of the chambers, if you were to get
an oxygen saturation from the descending aorta, it cannot be 99%.
All the blood is mixing together.
It's got to be somewhere between 95% and 75%, somewhere in the 80s or less, depending upon
the flow.
So on a newborn who has a heart murmur that you're concerned, get an arterial saturation
from the descending aorta.
If the saturation is 99%, then he has one of the milder things, either peripheral pulmonary
stenosis, or a PDA, or mild congenital heart disease.
And I don't think all those kids need echocardiograms.
I think you probably can have someone see them in a week or 10 days.
And most of them are going to have PDAs that the murmur's gone.
Those kids whose saturations are lower-- and people ask, what is the exact number?
I'm not sure there is an exact number.
I think the higher it is, the less likely you are-- if you're in the 70s or 80s, there's
no question something's catastrophically wrong.
If you're 98% or above, you almost certainly have nothing.
In between, it's a little bit more iffy.
And I think those kids, you can put them in a little bit of oxygen.
That will not change the saturation in children with critical congenital heart disease.
But if there's a little bit of atelectasis, it will make a difference.
I think you need to make sure you get a saturation in the descending aorta because there is a
disease where you can have normal saturations in the ascending aorta but abnormal in the
descending aorta.
And that's left-sided disease where, instead of having hypoplastic left-heart syndrome,
you have a severe coarctation or interrupted aortic arch.
In these kids, the pink blood will go through left atrium, left ventricle and go to the
ascending aorta to the arm vessels and the head, but it's mostly descending aortic blood
that goes down below the diaphragm.
So it's important to get it in the descending aorta.
This concludes our video on Clinical Presentation of Congenital Heart Disease in the First Week
of Life: Murmurs.
Please continue with the next video in the series, Clinical Presentation of Congenital
Heart Disease in the First Week of Life: Arrhythmias.
Thank you.
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