“Clinical Presentation of Congenital Heart Disease:  Murmurs” by Michael Freed, MD

“Clinical Presentation of Congenital Heart Disease: Murmurs” by Michael Freed, MD

March 7, 2020 1 By Bertrand Dibbert

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. Please help us improve the content by providing
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