Voiceover: So we're looking at a fetal heart,
that's the heart in a baby
before the baby is even born
and there are two things I want to point out.
First thing is that the blood that's returning
to the heart is gonna be picking up some
important stuff from the placenta.
So here we have the placenta where
the mother's blood is coming in
and when that blood is coming in,
it's gonna give off two very important things.
It's gonna give off oxygen,
so let's say these are the oxygen molecules,
so it's gonna give off that oxygen and -
so O2, and it's also gonna give off prostaglandins,
in the future I'll just call that PG
All right, so it's giving off oxygen,
which, of course, is very important
and prostaglandins and as the blood
is picking that up it is returning to the heart
and then it can be pumped to the rest of the body.
The next thing I want you to notice is that
we also have an additional connection here,
an additional artery that we call the ductus arteriosus
and the reason for that is, well,
in the developing embryo, in the developing fetus
we don't have the lungs being fully functional.
It's not breathing so it's not taking up
oxygen that way so we don't need a bunch
of blood going via these pulmonary
arteries through the lungs.
Instead, they can come via the pulmonary arteries
and then go via this ductus arteriosus
so that via this larger vessel, which is your aorta,
we can go to the rest of the body.
Now when the baby is born,
some important things happen.
The most important thing where this is concerned is,
I'm gonna draw one lung here,
it's kinda small in this picture,
the most important thing is that the baby
starts to breathe so the lungs, the fluid in the lungs,
is gonna come out when it starts to cry
and it's gonna take in that air and all that stuff
and what we're gonna have is now the blood
can come to the heart without oxygen -
not to the heart, to the lungs, sorry,
without oxygen and then it can go back
to the heart with oxygen
so it's picking up oxygen in the lungs.
Now once all of these things are happening,
what happens is this ductus arteriosus,
we don't need it anymore so it can close.
But in some individuals, that doesn't close
and that's what we call patent ductus arteriosus.
The word patent means open
so the ductus arteriosus remains open.
Now why would that happen?
Well, let's talk about closure, why does it close?
And if we understand why it closes,
we'll understand why in some situations
it might remain open.
So the first thing is that if we have that increase
in oxygen because of the fact that the baby
is starting to breathe, that is gonna be
the main factor stimulating this to close.
The second one is because of the prostaglandins,
a reduction in prostaglandins
because, of course, when the baby is born
you cut the umbilical cord, it's no longer
connected to the placenta so the prostaglandins
that it was getting from the maternal blood,
the mother's blood, it is no longer getting
so those levels are gonna decrease.
So what would keep it open?
Well, we know what would keep it closed
so if for some reason one of these two factors
are compromised, that is gonna cause it
or that can cause it to remain open.
So let's say the baby was born prematurely
and because of that, the lungs are not
fully developed so the oxygen exchange
isn't gonna happen as well and this remains open.
Or let's say we have high levels
of prostaglandins in the fetal circulation
or an increased sensitivity to those prostaglandins
so the heart is responding even more to
those prostaglandins, that is gonna remain open.
There's another factor that's unrelated
so I'll write it down here
and that is when mothers are infected with rubella.
It's kinda like a type of measles.
When that happens, the chances
of this staying open, the ductus arteriosus staying open
is gonna be significantly higher.
We don't fully understand the exact mechanism
as to why that's the case,
but we do know that it does happen.
So how is it gonna manifest itself?
How do we know that an individual -
how is this detected?
Well, one of the first things is, you know,
when the baby is born, one of the things
that they do is they take the stethoscope
and they go and listen to the heart.
And in this case, when they listen,
you can hear, of course, if blood
is flowing through this place
where it's not supposed to flow,
you're gonna hear that squirting through that tube
and that is one of the things that they listen for.
Some of the other things that we see is
what is called a widening pulse pressure.
So if I were to draw a graph over here
so that we can look at blood pressure -
so this is my graph and we have pressure over here,
I'll just put press, pressure over here,
and time over here and we were to look
at a graph of the blood pressure,
of course, we're gonna have something
that looks like this.
It's going between high and low.
This top point is your systolic pressure
or your SP, let's put SP,
and this part here is your DP,
which is your diastolic pressure.
This is during contraction
and this is during relaxation.
Now if you have blood that's leaving
the normal circulatory path going to the body
and it's going back to the lungs,
the pressure in the arteries throughout the body,
the diastolic pressure is gonna be less
because you're pushing more out,
so you have more leaving
so that diastolic pressure goes down.
And because this is an inefficient system,
eventually what happens is the heart
is gonna have to do more work
and as the heart is doing more work
that's gonna increase that systolic pressure.
So the difference between systolic and diastolic,
or the pulse pressure, is gonna be larger
so you're gonna have a wider pulse pressure,
the difference between systolic and diastolic.
Not only that - okay, so let's say
we have this situation where blood now
can leave via this ductus arteriosus in a newborn baby.
We have significantly higher pressure
on the left side because that's doing much more work,
sending the blood all throughout the body
and because of that we're gonna get blood
that is leaving via the ductus arteriosus
and then going back to the lungs.
So we get significantly more blood going to the lungs.
If you get significantly more going to the lungs,
that can then cause respiratory problems.
You can get problems with the respiratory system,
with the lungs and their function.
Also, because now the heart is doing more work
to push through this inefficient system,
you can end up with an enlarged heart
where the muscles are getting larger
because they're doing significantly more work.
So the question is how do we treat this?
So let's do that in a brand new color.
So let's do it in green, so treatment.
Now there are some medications that can be used.
One class of drugs that's often used
to treat individuals that have
patent ductus arteriosus is called NSAIDS
and what that stands for
is nonsteroidal anti-inflammatory drugs
and what that does is it inhibits prostaglandins.
All right, so we have an inhibitory effect
to these prostaglandins, reducing their levels,
and that is gonna cause it to close.
And then we can have some surgical treatments
and there are two main types.
The first one is gonna be called PDA ligation.
What we're basically doing in that case is
we're gonna tie this off at the beginning and at the end
and by tying it off you're cutting off
the blood supply here and then that's
eventually gonna deteriorate.
The second option is what we call coil occlusion
and with that, it's kind of the similar principle,
but we're using a different system.
So what we're gonna do there is
we're literally gonna insert a coil through
that ductus arteriosus that blocks the blood flow
and then that is gonna cause it
to be occluded or stopped up so that
blood cannot travel through and that,
in effect, eliminates the problem of blood
leaving through that ductus arteriosus.
So those are the ways that it can be treated.
We either target the prostaglandins
or we try to surgically close
the ductus arteriosus off.