00:01
Let's move on to tetralogy of Fallot.
00:06
Tetralogy of Fallot is the most common cyanotic heart disease
and it frequently shows up on multiple choice tests.
00:14
So I think it's important to go through tetralogy and really understand what it is.
00:19
It's important to memorize the four findings in the tetralogy
and I'm going to go through them now for you.
00:25
There are four major findings and it can look pretty complicated.
00:31
But if I go through it one step at a time, I think you'll understand it.
00:36
Here we go.
00:39
On the left side, you can see a normal heart.
00:43
On the right side of your slide, you can see tetralogy of Fallot.
00:48
I'm going to walk through the tetralogy, the four findings in tetralogy,
and I'm going to make it so you're convinced that it's not as complicated as it sounds.
00:56
Let's start with an overriding aorta.
00:59
In these patients, there is that connection between the two ventricles called the VSD.
01:07
The aorta rides over that VSD and allows the mixed blood to go into the aorta.
01:15
That's why these infants are cyanotic.
01:17
Some of that right-sided blood is shunting to the left
through that VSD and up into that overriding aorta.
01:24
Two of the findings in tetralogy are overriding aorta and VSD.
01:29
When you hear "tetralogy," it's not really true.
01:33
Maybe you could call it triology of Fallot because you couldn't really have an overriding aorta without a VSD.
01:40
if you imagine how could the aorta ride over both ventricles unless there's a hole between them?
Additionally, these patients have some pulmonary stenosis.
01:51
Basically, as that area shifts over and you're allowing for that overriding aorta,
there's a squeezing of the pulmonary artery allowing for stenosis.
02:04
That narrowed pulmonary stenosis results in a right ventricular hypertrophy.
02:11
Really, it's the biology of Fallot in that you're both having the VSD and the overriding aorta,
and the pulmonary stenosis resulting at right ventricular hypertrophy.
02:26
However, realistically, this is just one thing.
02:31
You could call it "The Fallot" if you want.
02:33
The abnormal rotation of the conotruncal septum at the top part of the heart
is it's abnormally rotated as opposed to the intraventricular septum -
the bottom part of the heart -
and this whole shifting results in all of these findings.
02:52
It's really just a shifting of the upper part against the lower part of the heart that results in the full tetralogy.
02:59
That might make it a little bit more clearer.
03:03
It's important to understand that children who have a high-degree of pulmonary stenosis
are going to be sicker than children who have less pulmonary stenosis.
03:13
The key thing about how blue a baby is at birth is how much pulmonary stenosis there is.
03:20
In a baby with a lot of pulmonary stenosis,
more of that blood is going to get shunted over to the left side.
03:26
In a baby with less pulmonary stenosis,
it's going to go right up into the lungs,
and that's going to be the distinguishing feature between a baby who's what we call a "pink tet" -
someone with less stenosis and less cyanosis -
versus a "blue tet" -
a baby who has a lot of pulmonary stenosis and a lot of blood shunting.
03:47
Additional points that are high-yield are the boot-shaped appearance of the heart on CXR.
03:52
And the role of squatting in increasing peripheral vascular resistance and thus decreasing the magnitude of the right-to-left shunt.