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Health and medicine
Course: Health and medicine > Unit 3
Lesson 13: Cyanotic heart diseases- What is cyanotic heart disease
- Shunting in the heart
- Einsenmenger coarctation of aorta
- Tetralogy of fallot
- Truncus arteriosus
- Total anomalous pulmonary venous return
- Tricuspid atresia
- Transposition of great arteries
- Ebstein's anomaly
- Hypoplastic left heart syndrome and norwood glenn fontan
- Cyanotic heart diseases - Diagnosis and treatment
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Tetralogy of fallot
Created by Amy Fan.
Want to join the conversation?
- How do people develop Tetralogy of Fallot in the first place? Are people with Tetralogy of Fallot born with the VSD and overriding aorta, and then pulmonary stenosis and LVH develops? Or does it develop another way?(2 votes)
- It's congenital: babies are born with all four defects, thus the name: Tetra (four) logy of Fallot (Fallot is just the scientist who discovered the defect).(2 votes)
- Since Fallot was a French physician, shouldn't his name be capitalized? Other sources on the internet describe this condition as Tetralogy of Fallot.(1 vote)
- How do we gauge a pulmonary stenosis. If a 7 month old baby had a VSD, righ ventricular hypertrophy , patent foramn ovale, PDA and a pulmonary artery diameter of 2.2 cm does this constitute a TOF.(1 vote)
- Those are all symptomatic of a TOF so that might be a reasonable diagnosis.(1 vote)
- What is ejection systolic murmur(0 votes)
- It is a crescendo-decrescendo murmur between S1 and S2. Before the murmur, there is an extra heart sound called ejection click. The systolic ejection murmur indicates Aortic Stenosis.(1 vote)
Video transcript
- For Tetralogy of
Fallot, don't worry about what Fallot means. That's just the name of the
guy, this French physician, who named this disease. So we wanna focus on the first word here, which is tetralogy. And going back to Latin
here, tetra, tetralogy. The word is telling us that there are four defects that we care about, that make up this particular heart disease. Remember that this is
congenital, so people are born with these four defects in the heart. But first let's quickly review
what a normal heart does. The blood from the body that
returns to the heart initially is gonna be blue because
it's lower in oxygen. The muscles have used up the oxygen. So it returns to the heart
into the right atrium, the receiving chamber. From there it goes to the right ventricle, which pumps it into this blue vessel, which is the pulmonary artery. Remember that any vessel
that receives blood going out of the heart is an artery. So even though it's an artery, it's still blue, de-oxygenated blood. From the lungs, red oxygen
in the blood returns here via the pulmonary veins,
into the left atrium. From there it goes to the left ventricle, and it goes out this big
red structure, the aorta, to the body. So in tetralogy, the first
defect that we worry about, some would argue it's
the defect that governs how this heart functions, is
called pulmonary stenosis. So pulmonary, you know,
has to do with the lungs. In this case, it's referring to the valve that leads blood to the lungs. So the pulmonary valve is right here. Stenosis is a stricture or narrowing, so this pulmonary valve here is thickened. So as the right ventricle
is pumping blood into it, it is harder to pass through it because it's literally just thick and restricting. So the degree of pulmonary
stenosis determines how hard is it to pump blood into
the pulmonary arteries, and determines how severe this
heart is functionally damaged. Now our second defect is
a direct result of this, and also depends on
the degree of stenosis, and that is right ventricular hypertrophy. So imagine trying to pump
blood against a narrow opening, day in and day out. Hypertrophy is when the
muscle is over exercised and over used and it
literally becomes bigger. So the right ventricle,
this chamber right here, becomes thicker to assume the
extra workload that it has for pumping against this narrow valve. So a lot of times this
hypertrophy is enough to alter the shape of
this right ventricle here. So do you see in the way
I've drawn it before, it has this nice slope. So if our normal heart follows a curvature kind of like this, in tetralogy
the shape can actually look more like this. It comes down here, right angle. And that's why some people
actually say, on x-ray, when just looking at the
growth shape of the heart, that it'll look like a boot. So the boot sign is
something that we associate with tetralogy because of
the severe right ventricle hypertrophy that can happen. Alright, let's move on to the third one. So usually there is a hole between the right and left ventricle,
the bottom chambers. I'm gonna draw this hole right here. It can actually be
anywhere along this septum. And we call it a VSD, which
stands for ventricular. It tells you where it is,
it's between the ventricles. Septal, which is the wall,
the septum between them. Defect, we have a hole. OK, I'm gonna draw this right here. So now in the machinery of the heart, we have a connection
between the left and right. And now for the last defect,
we have an overriding aorta. What is the overriding? So the aorta is usually plugged
into the left ventricle, but overriding means that
it actually receives blood from both left and right now. And from the place I've drawn as the VSD right under the aorta, I
could almost just leave that like this, but just
to drive the point home, I wanna redraw this part, that the aorta comes over to the right and is now this kind of central structure. Now from here, now it can receive blood both from the right and the left. So now let's think about
if I'm a drop of blood, where I want to go in this new heart with these four defects. So from the right atrium,
go to the right ventricle, that's normal. So if I'm here, I have a choice, right? I can either go up this pulmonary artery, through this very narrow
opening in the valve. That's gonna be difficult. Or I can easily go into
this aorta with a valve that's more welcoming,
that's less restricted. See I draw these two arrows
with different calibres 'cause I'm leading you to the answer, which is that I want to go
this way, into the aorta. Also in general, blood
in the right ventricle is gonna be pushed toward the left because look at how big the
right ventricle is now. It's this huge powerful muscle,
and it serves as the motor that drives this right to left shunt. And therein you have the
answer for why this is a cyanotic disease, because blue blood is being forced to the left. Because A, it's hard to go
through the pulmonary artery where it's supposed to go,
and B, the right ventricle is so powerful, it's gonna
push it across the VSD. Remember, blood follows the easiest path. So the left ventricle is still pumping, and the blood is basically
gonna go into the aorta. So now in the aorta going out to the body, we have red blood and we have blue blood. So what actually goes
out to oxygenate our body is this purplish mixture. Purple, some blue, some red. And at any given moment,
how blue it is or how red depends on the tug of war
between all these factors. How restricted is this pulmonary artery? How much resistance is
coming from the lungs? Remember the pulmonary arteries
are plugged into the lungs. How hard the right
ventricle is pumping blood across the VSD. So these are all factors
that determine how much our purplish mixture is red versus blue. Sometimes kids who have
tetralogy can have a sudden tet spell, which is
when they get acutely worse, and they can't breathe. That's because their
pulmonary artery pressure or resistance from the lungs,
has suddenly increased. All that does is create more back pressure in the pulmonary artery. It's already hard to get blood in here, and the tet spell makes it even worse. So a tet spell shunts more
blue blood into the aorta. This mixture becomes even bluer. This is a life-threatening
emergency in tetralogy. And lastly, I also wanna
talk about the fact that before people here knew
what tetralogy was, or what the heart actually looked like, we noticed that kids who
have it, or this type of kid, would suddenly squat onto the ground, especially when they've been
playing or running around. They suddenly feel a lot
worse, they'll squat, and they'll feel better. So here we have a kid- I always say kid because,
for the most part, this is still a pediatric disease. We correct it in the
patients when they're kids. So they're running around, let's
say they're four years old. And suddenly they'll stop and
they'll squat onto the ground. How do you draw a squatting stick figure? Does that make sense? That looks more like they're sitting. Let me try again. So they're squatting. There we go. And as they get into this
position for a few seconds, they feel better. So let's think through this step by step. OK, two things happen when
somebody with tetralogy- Or I guess anybody is running around. The first one is that the
O2, or oxygen saturation, in their veins drops because their muscles are working hard, and they're extracting more oxygen from it. So the blood going back
to the heart here and here have a lower oxygen content. And secondly, what happens
is that their vessels in their legs, or whatever
muscles they're using a lot, they vasodilate, so the body
can get more blood there. Literally their vessels in
their blood, the diameter goes from this to this,
it just gets bigger. So let's look at this one at a time. So if the O2 in the
veins drop, what happens? So the blood returning to the
heart is essentially bluer. So if the blood returning to the heart has a lower oxygen
concentration, and some if it goes right back out through the aorta, then running around has made
our blood bluer in the aorta. All this does is make our cyanosis worse. That's gonna make our patient
more blue in the face, and they don't feel good. For vasodilation, what
happens is this stricture, or the calibre of the
vessels, determines how much resistance is pushing back on our aorta. So the vasodilation really
lowers the resistance in the aorta. So in the competition
between the right and left, between the blue and the red,
again this makes us bluer, making this red structure
have lower resistance means more of the blue
blood will get into it. So again, we're bluer and more cyanotic. So now this child is
really not feeling well. And look when they squat, both
of these things are reversed. First of all, they stopped running around, so the oxygen content in
their veins can go up. So here they've got slightly
higher oxygen content in their veins just by stopping and trying to take deeper breath. And secondly, they're
literally taking their vessels in their legs and squeezing them, which increases their systemic resistance. This is the resistance of
all the arteries in the body. Systemic resistance. And since they're all
connected to the aorta, this increases the
resistance that the aorta is pumping against. So as these two colors
of blood rush at this general area, when the resistance
in the aorta increases, it literally just forces more blood into the pulmonary artery. So the competition is,
where is it harder to go? And when this child has
squatted, it is harder to go into the aorta at this
point, because it's like they've taken the end of a hose and they've squeezed it down. So this just forces more blood
into the pulmonary artery. It's still restricted, but the difference between the two has lessened. So more blood goes into
the pulmonary artery. This child will feel
like it's easier to take some good breaths, and
this will also increase the return of oxygenated blood into the left side of the heart. So the whole effect is that we reverse the shunt a little bit. We get more blood out to the lungs and the pulmonary artery,
and we just increase the overall oxygen content
in our mixture a little bit. So when we think of
tetralogy, the things that most determine how bad or how severe a person's symptoms are. One, the pulmonary
stenosis, how severe is it? And two, where is the VSD? So I would like of tetralogy
overall as a constant fight, a tug of war, for the
heart to pump blood into either the pulmonary artery or the aorta. And the state of the mixture
between the red and blue blood determines this person's
symptoms at any given moment.