So let’s review the five types of cyanotic heart disease.
We’re going to go through each one, we’ll talk a little bit about each disease
so you can try and understand them a little better.
First, truncus arteriosus.
So, truncus arteriosus, you can see here.
On your left side is a normal heart.
And on the right side is a patient with truncus arteriosus.
What you can see in this patient with truncus arteriosus is the aorta
and the pulmonary artery have merged together and formed one main trunk
and that trunk is sitting over a VSD
So here’s the aorta and the pulmonary artery with our common origin
sitting over a VSD and this VSD is allowing the blood from the left and right
to mix together and then go up that common trunk.
So in patients with this disease,
they will have that common trunk with a single valve
and it’s supplying both the pulmonary and systemic circulation.
You can see then why this baby would be born blue.
The truncus overrides the VSD, which results in that mixing lesion.
These patients are managed surgically,
so we have to somehow repair this situation so that we’ve recreated a functional heart.
So you can see the single trunk with a single valve
is overriding both the pulmonary and the systemic circulation.
The VSD is allowing for blood mixture and is resulting in the baby being cyanotic.
Let’s move on to transposition of the great arteries.
This is also called transposition of the great vessels.
In this condition, the aorta and the pulmonary artery are switched.
Blood in a normal patient will come back from the inferior and superior vena cava,
down to the right atrium, to the right ventricle,
and then out to the pulmonary artery, which goes to the lungs.
As you’ve learned, blood then comes back from the pulmonary vein
into the left atrium,
the left ventricle, and then out the aorta to the body.
In a patient with transposition of the great vessels,
these two main vessels have switched,
which creates two parallel circulations.
In one of these patients, the blood comes from the inferior and superior vena cava
into the right atrium, the right ventricle, and it goes out to the aorta.
That blood now comes back from the body
and goes back into the right atrium, the right ventricle, and into the aorta.
You can see how we don’t ever get blood to the lungs that way.
But they do because there’s another parallel circulation going on,
where the blood is coming from the lungs back to the left atrium,
to the left ventricle, and out to the pulmonary artery.
So this blood is circulating around to the lungs,
and then you have another system that’s circulating around to the body.
These patients will require a mixing lesion,
such as a patent ductus arteriosus,
or a VSD, or an ASD,
and those mixing lesions will allow this patient to continue to survive.
That mixing allows some of the blue blood to get over the lungs
and some of the pink blood to get over the body.
But you can see why in a hyperoxia test
this child would have a very, very low level of oxygen
because boosting the amount of oxygenated blood in the pulmonary system
is not going to necessarily improve the oxygen in the body.
You’re really just relying on that mixing area.
In these patients, they need an arterial switch operation.
It’s a bit complicated also and they usually require a catheterization
because remember, the coronary arteries can be coming off the left side,
or the aorta, or they can be coming off the right side
and you have to know where those coronary arteries are
to fully fix the problem surgically.
So again, the right ventricle goes to the aorta,
the left ventricle goes to the pulmonary artery,
and the ductus or the VSD or ASD is keeping that patient alive.
This patient, if you get an X-ray, will have a classic egg on a string appearance,
where it looks like a sideways egg
floating underneath a string with a very narrow mediastinum.