- When we talk about cyanotic heart diseases
we'll come back to what cyanotic means
in just a second.
So, congenital means that
it is something that the person was born with.
So they have heart disease not because they didn't eat right
or something was wrong with their environment,
but because their heart is structurally abnormal.
And these days, with all the technology,
we can actually ultrasound the mom's belly
and see that this baby has congenital heart disease
because, again, this is something structural
that we can physically see with our eyes.
For cyanotic, I think the best synonym to use is blue.
So blue, in medical terms,
means this baby looks blue.
And by the way, I'm going to keep saying baby,
because when we think of congenital heart disease
we're usually talking about babies
because they need treatment early.
And yes, they do survive into adulthood
which is nice, but when we talk about treatment
or diagnosing, most of the time we're dealing
with the pediatric world,
so this baby is blue.
Now babies can look blue for lots and lots of reasons.
It could be a lung disease thing,
it could be something with their circulation,
but obviously, for our purposes,
we care about their heart making them blue.
So this is a baby, the most obvious ways
to see this bluish tint in people of all colors,
are the mucus membranes, so the whites of their eyes
might turn blue, their lips,
and the tip of their tongue is a good place.
Sometimes, if it's really severe,
their body will start to become cyanotic,
and that's how you know they really
are lacking oxygen.
So to go back even further,
we have this idea in medicine
that when blood has a lot of carbon dioxide
in it, it is blue, and blood with oxygen in it, is red,
how we usually think of blood,
and this is true to a certain extent.
Blood that has less oxygen in it
has a darker tint, but is not actually blue.
For our purposes, we'll keep it that way.
So we just want to go over the function
of the heart really quickly.
This is not going to be anatomically correct.
This is my schematic of the heart,
and we have our four chambers.
I'm just going to go over, roughly,
what the heart does.
So the top two are the atria.
So this is the right atrium.
The other thing is, this is going to be right,
and this is going to be left.
That's just how it is designated in medicine,
because when we look at an xray
or a film, it is usually flipped like this.
So, let's get used to the right side
being on the left side.
So the right atrium, left atrium.
The right ventricle, these bottom chambers
are going to be ventricles,
they are the big pumping chambers.
And the left ventricle.
So, blood from the body that's been used up
by the tissues, the oxygen's been used up,
it's going to be a bluish blood.
We think of it as deoxygenated blood.
Blood with a lot of carbon dioxide,
or CO2 in it.
This gets returned to the right atrium first.
From there, it goes to the right ventricle.
There's going to be a valve here.
Actually, there are going to be valves
between each of the chambers and places,
and those are some of the places
that can be structurally abnormal
in congenital heart disease,
but we'll worry about that in just a second.
From the right ventricle,
it gets pumped to the lungs.
And the lungs is where we pick up oxygen,
that's why we breathe in and out,
getting oxygen into our blood.
So blood coming out of the lungs, then,
is going to be red, because oxygen
has been added to it.
So red blood returns to the left atrium.
Have you noticed that the atria seem
to receive blood from outside the heart?
These are the receiving chambers.
So it flows into the left ventricle.
The left ventricle is the most powerful one,
because it has to pump blood really far
to the rest of the body, so now we have this person
that's red because they have more oxygen in their blood.
And just for completeness sake,
vessels that receive blood from
the heart are called arteries.
So we have red blood usually traveling in the arteries.
Delivers it to the tissue,
oxygen leaves to go work in the tissues,
in other words oxygen is extracted
the blood goes into veins,
and veins are vessels that return blood to the heart.
So usually, in a healthy person,
we want the oxygen content in arteries
to be above 90 percent.
For a healthy person, is actually usually around
98, 99, but above 90 percent we can live with.
We like that.
So now the oxygen in the veins
will obviously be less than 90 percent.
We're probably happy with 70s, 80s,
it depends on a lot of different factors.
So you see that when we think of arteries and veins,
we expect them to have different levels of oxygen.
So what is cyanosis then?
I said before that this blueness comes
from the blood not having enough oxygen,
and here we're talking about arteries.
Vein oxygen content, yeah, we care
in some circumstances, but right now,
for congenital heart disease,
we care about arteries (mumbles) enough oxygen.
So what exact level we have cyanosis
kind of is a little bit dependent on the person.
But we know for sure that it is less than 90 percent,
so in this case, cyanosis starts to happen
around 80 to 85 percent oxygen.
It's a nice ball park.
It might go up and down depending
on if this person is anemic,
how well their lungs are working,
all these things vary.
But in general, cyanosis tells us that we're
definitely less than 90 percent,
and we're somewhere in the 80s ball park.
If we drop below that, it starts to be very dangerous.
So people can live in the 80s.
If we drop much lower than this,
it starts to get dangerous and life threatening.
People can live in the 80s for the saturation of oxygen.
It's not ideal, but they can definitely live here.
For some congenital heart diseases,
getting them to the 80s is kind of the best we can do.
But we don't use cyanotic,
a disease, as kind of a clinical way to assess them.
It's more of a category that separates
cyanotic from non-cyanotic heart disease.
There are heart diseases that you can have
structural abnormalities where
even though your heart doesn't have great function,
your artery oxygen saturation doesn't get affected.
This baby will stay nice and pink above 90 percent.
So this is really a category that we're talking about,
cyanotic versus non-cyanotic.
Without going into too much detail,
if we just look at this rough diagram of the heart,
cyanotic diseases, as a general rule,
will involve some sort of mechanism
for the blood to be mixing in a way
that the right is shunting to the left.
Shunting talks about something
that was supposed to be over here
being pushed over there.
So as you can see the right side of the heart
is this blue blood, when it gets pushed over here,
then we mix, and we drop the oxygen saturation over here.
So just in the back of your mind,
think about right and left shunting,
and how the blood is mixing this way,
when we talk about specific cyanotic heart diseases.