Laster

Video transcript

- [Voiceover] The other day one of the pediatric cardiology doctors was joking around with me and we were talking about Epstein's anomaly. He said "I say Epstein's and you say?" And the answer is Lithium. So, in the minds of a lot of students when you're taking tests, Epstein's and Lithium always go together. So, the theory is that mothers who take Lithium, which is a drug to treat bipolar disorder, that's what leads to their children having Epstein's defect when they develop that in the uterus. Now, according to this doctor I was talking to, this is just something we've taken for granted for a long time and it's not really backed up with a lot of evidence. It's just one of those heart defects we think of as caused by drugs the mother can take. But, in reality, it can also happen in babies whose mothers are not taking Lithium. So, Epstein's is a defect that involves the right side of the heart. We have our right atrium, right ventricle, down here, left atrium, left ventricle, blue pulmonary artery, red aorta. So, in Epstein's we have something happening in the tricuspid valve, which is usually here, between the right atrium and right ventricle. And it basically drops downward. We call it displaced. It's almost like it has fallen off towards the ventricle. So, the way I'm drawing this, it's going to look really awkward because I'm trying to modify, instead of redrawing this thing. It's just to show you the right atrium extends down here, now. So, the right ventricle is still connected to pulmonary artery, but now, the right ventricle is tiny. It's this area down here. And the tricuspid valve, again, it's between these two chambers. But, it's usually underdeveloped or floppy or something is wrong with it. There's a word associated with Epstein's. We call it the "atrialization" of the right ventricle. Let's see if I can spell that, a-trial-ization. It basically just means because the tricuspid valve that separates the two drops down, then this whole area above that used to be the right ventricle, or is supposed to be, now is the atrium. So, the atrium is bigger, the ventricle is smaller. This makes the right ventricle pretty wimpy. It's small and weak. Now, let me come in and draw the septum between the right and left atrium that separates the two top chambers. In as many as half of the people with Epstein's, there's a whole between the right and left atrium. So, we have our atrial septal defect or ASD. De-fect. Okay, so this is how Epstein's is set up. The left side works the same. So, red blood comes back in to the left atrium from the lungs and the left ventricle pumps it to the aorta. So, why do we have cyanosis? Let's start from the beginning. When this baby is first born, keep in mind that when the baby's first born the lungs have very, very high resistance. As much as four times the amount of resistance that adults have. So, in our pulmonary artery, here, we got a huge force going this way. So, if your drop of blood, deoxgenated blood, from the body going into the right atrium, which is now huge, go to the right ventricle. If a choice between going into the pulmonary artery, here, or going back through the tricuspid valve. Let me just label that really quickly. Tricuspid. Remember that it's dropped down and it's not working perfectly. So, the blood can't actually get back behind the tricuspid valve, back into the atrum and go across, shunt across, to the left side, here. So, especially in the beginning of life with this high pulmonary resistance, the blood favors this route going to the left side. So, we have a big strong shunt this way. This results in the left atrium having, again, mixed blood. So, we have blue from the right side and red coming from the lungs and we got purple blood going into the left ventricle and purple blood going out to the aorta. So, cyanosis from this mixing, also, from the fact that we're not getting too much blood to the lungs. So, you remember from this particular way of shunting, we can kind of think of the right atrium or right ventricle as just one blob of things. The valve, here, is not working too well to keep it two separate places. So, as the wimpy right ventricle tries to squeeze whatever power it can generate, it usually pushes the blood over to the left side, instead of through this high-resistance pulmonary artery. Now, as soon as the baby is born, the resistance in the lungs begin to drop. So, this might be the one disease that actually gets a little better as this child gets into the first few weeks of life. So, I just erased the arrows, talking about our resistance and with that the size of the shunt gets a little smaller. So, there's still some shunting. And redraw the arrow like that. There's still some shunting. But now, we got more blood go into the pulmonary valve, as the resistance in the lungs keep dropping until it's at a normal adult level, then more and more blood will go into the lungs. So, this disease actually gets better as the kid gets older. Because all we care about is the resistance in here dropping enough, so that most of the deoxygenated blood goes to the lungs instead of to the left side, then we have less mixing and that will give the left side more red blood instead of purple. And that's basically all we care about is, functionally, how strong the shunt is. So, as long as most of the blood is going to the lungs, then we're okay. Not to say that people with Epstein's don't need surgery or treatment because most of the time they don't just have Epstein's. They have something else that might need to be repaired. But, as far as, this particular thing we've talked about, remember that it get's better as the pulmonary resistance drops. And there's a chance that this child might get away without surgery.