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- [Voiceover] In cyanotic heart diseases, usually we're talking about a right-to-left direction of shunting. The bluer, less oxygenated blood on the right side is going to the left side and out to the body. That's why we become blue, or cyanotic. Now the counterpart to cyanotic diseases are the ones that are not cyanotic, obviously. The shunting in these situations go from left-to-right. So we have the red blood going into the deoxygenated part. All we get is blood going to the lungs having a higher content of oxygen. This doesn't turn anybody blue so they're not cyanotic. Ah ha, but there's a catch. There's something that can happen later on in this child's life that suddenly turn them cyanotic. An example I want to use to talk about all this is a heart disease called coarctation of the aorta. Coarctation. It's a fancy word for restriction. Coarctation of the aorta. So like I said, it's a restriction of the aorta. And it looks like this. So instead of our nice big aorta that we had before, in this case the aorta comes down here and woop there's a little coarc there. Right there. Actually it could be anywhere but that's one of the most common places to have it. Then the rest of it goes on. So this little squeeze here creates a lot of resistance. Resistance. Because there's a lot of blood flowing through the aorta at any second. And to have this bottleneck here creates a lot of resistance which again increases the pressure. So now we have the left side having even more pressure than before and coarctation can be its own isolated defect but sometimes it also involves a VSD. Ventricular septal defect. That just means a hole between the two ventricles. So here we have RVSD. So if we have both, just to drive home the idea of the shunt, think about, so the blood going into the aorta has a lot of resistance here and then it's gonna back up right into the VSD. So the shunting goes this way. So let's say we don't fix this coarc. No surgery, this child grows up. They'll have kind of compromised flow of blood into their system. But they can survive. Now all the while we have left-to-right shunting. We can live with that. But imagine what happens to a muscle, specifically to the right ventricle muscle, that is receiving more volume of blood than it's used to, even if there's no shunting here and the right ventricle does its job by pumping to the lungs. But with all this shunting, we have all this extra volume of blood to the lungs day in and day out. Any time you exercise a muscle too much it becomes thicker and stronger. So imagine this right ventricle is thickening. It's learning to work harder and harder. I'm just going to draw it in here to drive home the point. So now we have this thick wall at the right ventricle. Now remember that the left and right ventricles squeeze together at the same time. And usually the left ventricle is so strong that we get blood this way. And then one day finally the right ventricle has grown big enough it's going to give one big squeeze and it's going to overpower the left ventricle and the blood is suddenly going to go this way. So instead of our left-to-right shunt, now we're going right-to-left. Because the right ventricle now has the greater power. This is the phenomena of the reversal of the shunt now going right-to-left because the right ventricle has grown so big. This is what we call Eisenmenger. Eisenmenger, depending on how you want to pronounce it. And this usually happens around age five or six, depending on the child and what their actual structure looks like. And I used blue here because suddenly our shunt is going from deoxygenated blood to oxygenated. Now the mixing happens the other way and now the child is cyanotic. I just threw in the coarc here to drive home the point but even if this child just had a VSD it would be the same thing. Initially we would have left-to-right going this way with a big left ventricle. And eventually it'll reverse. So Eisenmenger just refers to this reversal of the shunt. So just because you're born with a left-to-right shunt, doesn't mean you get out of being cyanotic forever. There's always the potential to reverse the shunt, end up having cyanotic heart disease.