Welcome to another video where medical topics are made easy.
Today I’m going to show you a simple trick to remember the main cyanotic congenital heart defects.
This commonly shows up on medical and board exams, so it’s worth learning this quick trick.
You can find the notes and study guide for this video linked down below.
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So let’s get right into it!
Congenital heart defects are structural abnormalities of the heart or great vessels occurring during
fetal development.
You may also hear of them referred to as congenital heart diseases, or CHD.
CHD can be subdivided into 2 types: cyanotic and acyanotic.
Cyanotic defects are heart defects in which the blood pumped to the rest of the body contains
less than normal amounts of oxygen.
In other words, the heart is pumping mixed blood containing both oxygen-poor and oxygen-rich
blood to the rest of the body.
This can lead to cyanosis which is a bluish discoloration of the skin.
Cyanotic heart defects contain right-to-left shunts meaning deoxygenated blood from the
right heart mixes with oxygenated blood in the left heart.
This causes oxygen-poor blood to get delivered to the rest of the body.
Acyanotic defects are heart defects that can affect the normal flow of blood but blood
oxygen levels delivered to the body typically remain normal.
Acyanotic heart defects often contain left-to-right shunts in which oxygenated blood from the
left heart mixes with deoxygenated blood in the right heart.
So with acyanotic defects the blood delivered to the rest of the body still remains oxygen
rich which is why there is no cyanosis.
In this video, we’re going to focus on cyanotic congenital heart defects and go over a simple
memory trick to remember them.
Here is a list of the main cyanotic congenital heart defects.
In other words, they’re the heart defects that can cause cyanosis.
The first trick is you can see they all start with the letter “T”.
So when you see a congenital heart defect on an exam that starts with a “T”, there’s
a good chance it’s a cyanotic heart defect.
Now the cyanotic defects shown can be tough to remember, so let’s go over a trick to
help you with this.
The trick is to count them off on your fingers.
Let’s go through the defects one by one so you can see how it works.
The timestamps for each defect are linked below.
The first cyanotic heart defect is truncus arteriosus.
You can hold up 1 to remember this.
Truncus arteriosus is when one blood vessel leaves the heart instead of 2.
You might remember from the anatomy of the heart video that normally there are 2 main
arteries leaving the heart.
The pulmonary artery leaves the right side of the heart and delivers deoxygenated blood
to the lungs, and the aorta leaves the left side of the heart and delivers oxygenated blood
to the rest of the body.
However in truncus arteriosus, the great vessel coming out of the heart fails to divide during
development, leaving a connection between the aorta and pulmonary artery.
As a result, there is a ventricular septal defect, or a hole between the right and left
ventricles, and one great vessel leaves the right and left ventricle.
As a result, both oxygen-rich and poor blood is delivered to the body.
And this can lead to potential cyanosis.
So again, you can use the number 1 to remember truncus arteriosus and one great vessel leaving
the heart.
If you need more information on the normal anatomy and blood flow through the heart,
you can check out the previous videos in the cardiology playlist.
It’ll be linked below as well.
The second cyanotic heart defect is transposition of great arteries.
This time you’re going to hold up 2 fingers,
and you can even cross your fingers to represent the transposition.
Transposition of great arteries is when the 2 main arteries leaving the heart are transposed
or reversed.
Remember we said the main pulmonary artery normally leaves the right heart and goes to
the lungs, and the aorta leaves the left heart and goes to the rest of the body.
In transposition of great arteries, the pulmonary artery and aorta are reversed, so the main
pulmonary artery arises from the left ventricle instead of the right, and the aorta arises
from the right ventricle instead of the left.
This creates 2 separate circuits, where deoxygenated blood in blue flows from the right side of
the heart to the rest of the body instead of the lungs, and oxygenated blood in red
flows from the left side of the heart to the lungs instead of the rest of the body.
So there needs to be a connection between the 2 circuits to allow for oxygen-rich and
poor blood to mix.
So there is typically a patent ductus arteriosus or a ventricular septal defect present.
As you can imagine, this will lead to deoxygenated blood being delivered to the body and subsequent
cyanosis.
So again, you can use the number 2 and cross your fingers to remember transposition of
great arteries and how the 2 great vessels are reversed or transposed.
The third cyanotic heart defect is tricuspid atresia.
For this you’ll hold up 3 fingers.
Tricuspid atresia is a congenital heart defect in which the tricuspid valve fails to form.
Remember in our medical terminology video, the prefix “tri” means 3, so holding up
3 fingers will help you remember tricuspid atresia.
Remember from the anatomy of the heart video that there is a valve between the right atrium
and right ventricle called the tricuspid valve.
In tricuspid atresia, the tricuspid valve fails to form and blood from the right atrium
cannot enter the right ventricle.
Instead there is an atrial septal defect, or a hole, which allows blood to pass from
the right atrium to the left atrium.
So now the oxygen-poor blood from the right heart mixes with the oxygen-rich blood in
the left heart, leading to decreased oxygen levels in the blood going to the rest of the body.
And this can lead to cyanosis.
There are different types of tricuspid atresia, but the right ventricle is typically underdeveloped,
and a ventricular septal defect allows blood from the left ventricle to enter the right
ventricle and pulmonary artery.
So again, you can use 3 fingers to remember tricuspid atresia and how the tricuspid valve
fails to form.
The fourth cyanotic defect is tetralogy of Fallot.
For this you’ll hold up 4 fingers.
Tetralogy of Fallot is a tetrad of four heart defects.
Remember in our medical terminology video, the prefix “tetra” means 4, so holding
up 4 fingers will help you remember tetralogy of Fallot and that it’s a tetrad.
The tetrad includes pulmonary stenosis, which is narrowing of the pulmonary valve and main
pulmonary artery,
right ventricular hypertrophy, which is thickening of the ventricle wall,
overriding aorta, which refers to the enlarged aortic valve that seems to open from both
ventricles and sits on top of the ventricular septal defect,
which brings us to the ventricular septal defect, which is a hole in the wall between
the right and left ventricle.
The pulmonary stenosis, right ventricular hypertrophy, and ventricular septal defect
can alter pressure gradients and allow oxygen-poor blood to travel from the right ventricle to
the left side of the heart.
And this can lead to cyanosis.
So again, you can use 4 fingers to remember tetralogy of Fallot and how there is a tetrad
of four cardiac defects.
The fifth cyanotic heart defect is total anomalous pulmonary venous return.
You can hold up 5 fingers to remember this because there are 5 words that make up the
defect.
This is when the pulmonary veins connect to the systemic venous system rather than the
left atrium.
Normally the 4 pulmonary veins deliver oxygenated blood from the lungs to the left atrium.
In TAPVR, the pulmonary veins do not connect to the left atrium.
Instead they connect to the systemic venous system.
As a result, the oxygenated blood from the lungs mixes with the deoxygenated venous blood
from the body, and the mixed blood flows back to the right atrium.
Since the pulmonary veins are not delivering blood to the left atrium, there is usually
an atrial septal defect present to allow blood to travel from the right atrium to the left
atrium.
Remember the right atrial blood in this case is mixed oxygen-rich and oxygen-poor blood.
So the left side of the heart is receiving less than normal oxygenated blood and delivering
it to the rest of the body.
And this can cause cyanosis.
So these are the 5 main cyanotic congenital heart defects.
They all start with the letter “T” and you can count them off on your fingers.
Hit pause in the video and try to name all 5 and what their main defect is using the
counting method.
Use 1 finger to remember truncus arteriosus, which is 1 great vessel leaving the heart
instead of 2.
Use 2 fingers and cross them to remember transposition of great arteries which is when the pulmonary
artery and aorta are transposed or reversed.
Use 3 fingers to remember tricuspid atresia which is when the tricuspid valve fails to
form.
Use 4 fingers to remember tetralogy of Fallot which is a tetrad of cardiac defects.
Use 5 fingers to remember total anomalous pulmonary venous return, which is when the
pulmonary veins connect to the systemic venous system rather than the left atrium.
Hopefully this gave you an easy way to remember the main cyanotic congenital heart defects.
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