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Patent ductus arteriosus

Patent ductus arteriosus is a medical condition where a blood vessel called the ductus arteriosus does not permanently close after birth. Learn why the ductus arteriosus does not close, why patients with this condition have a wide pulse pressure, and how the disease is treated with surgery and nonsteroidal anti-inflammatory drugs (NSAIDs). Created by Leslie Samuel.

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Video transcript

Voiceover: So we're looking at a fetal heart, that's the heart in a baby before the baby is even born and there are two things I want to point out. First thing is that the blood that's returning to the heart is gonna be picking up some important stuff from the placenta. So here we have the placenta where the mother's blood is coming in and when that blood is coming in, it's gonna give off two very important things. It's gonna give off oxygen, so let's say these are the oxygen molecules, so it's gonna give off that oxygen and - so O2, and it's also gonna give off prostaglandins, in the future I'll just call that PG All right, so it's giving off oxygen, which, of course, is very important and prostaglandins and as the blood is picking that up it is returning to the heart and then it can be pumped to the rest of the body. The next thing I want you to notice is that we also have an additional connection here, an additional artery that we call the ductus arteriosus and the reason for that is, well, in the developing embryo, in the developing fetus we don't have the lungs being fully functional. It's not breathing so it's not taking up oxygen that way so we don't need a bunch of blood going via these pulmonary arteries through the lungs. Instead, they can come via the pulmonary arteries and then go via this ductus arteriosus so that via this larger vessel, which is your aorta, we can go to the rest of the body. Now when the baby is born, some important things happen. The most important thing where this is concerned is, I'm gonna draw one lung here, it's kinda small in this picture, the most important thing is that the baby starts to breathe so the lungs, the fluid in the lungs, is gonna come out when it starts to cry and it's gonna take in that air and all that stuff and what we're gonna have is now the blood can come to the heart without oxygen - not to the heart, to the lungs, sorry, without oxygen and then it can go back to the heart with oxygen so it's picking up oxygen in the lungs. Now once all of these things are happening, what happens is this ductus arteriosus, we don't need it anymore so it can close. But in some individuals, that doesn't close and that's what we call patent ductus arteriosus. The word patent means open so the ductus arteriosus remains open. Now why would that happen? Well, let's talk about closure, why does it close? And if we understand why it closes, we'll understand why in some situations it might remain open. So the first thing is that if we have that increase in oxygen because of the fact that the baby is starting to breathe, that is gonna be the main factor stimulating this to close. The second one is because of the prostaglandins, a reduction in prostaglandins because, of course, when the baby is born you cut the umbilical cord, it's no longer connected to the placenta so the prostaglandins that it was getting from the maternal blood, the mother's blood, it is no longer getting so those levels are gonna decrease. So what would keep it open? Well, we know what would keep it closed so if for some reason one of these two factors are compromised, that is gonna cause it or that can cause it to remain open. So let's say the baby was born prematurely and because of that, the lungs are not fully developed so the oxygen exchange isn't gonna happen as well and this remains open. Or let's say we have high levels of prostaglandins in the fetal circulation or an increased sensitivity to those prostaglandins so the heart is responding even more to those prostaglandins, that is gonna remain open. There's another factor that's unrelated so I'll write it down here and that is when mothers are infected with rubella. It's kinda like a type of measles. When that happens, the chances of this staying open, the ductus arteriosus staying open is gonna be significantly higher. We don't fully understand the exact mechanism as to why that's the case, but we do know that it does happen. So how is it gonna manifest itself? How do we know that an individual - how is this detected? Well, one of the first things is, you know, when the baby is born, one of the things that they do is they take the stethoscope and they go and listen to the heart. And in this case, when they listen, you can hear, of course, if blood is flowing through this place where it's not supposed to flow, you're gonna hear that squirting through that tube and that is one of the things that they listen for. Some of the other things that we see is what is called a widening pulse pressure. So if I were to draw a graph over here so that we can look at blood pressure - so this is my graph and we have pressure over here, I'll just put press, pressure over here, and time over here and we were to look at a graph of the blood pressure, of course, we're gonna have something that looks like this. It's going between high and low. This top point is your systolic pressure or your SP, let's put SP, and this part here is your DP, which is your diastolic pressure. This is during contraction and this is during relaxation. Now if you have blood that's leaving the normal circulatory path going to the body and it's going back to the lungs, the pressure in the arteries throughout the body, the diastolic pressure is gonna be less because you're pushing more out, so you have more leaving so that diastolic pressure goes down. And because this is an inefficient system, eventually what happens is the heart is gonna have to do more work and as the heart is doing more work that's gonna increase that systolic pressure. So the difference between systolic and diastolic, or the pulse pressure, is gonna be larger so you're gonna have a wider pulse pressure, the difference between systolic and diastolic. Not only that - okay, so let's say we have this situation where blood now can leave via this ductus arteriosus in a newborn baby. We have significantly higher pressure on the left side because that's doing much more work, sending the blood all throughout the body and because of that we're gonna get blood that is leaving via the ductus arteriosus and then going back to the lungs. So we get significantly more blood going to the lungs. If you get significantly more going to the lungs, that can then cause respiratory problems. You can get problems with the respiratory system, with the lungs and their function. Also, because now the heart is doing more work to push through this inefficient system, you can end up with an enlarged heart where the muscles are getting larger because they're doing significantly more work. So the question is how do we treat this? So let's do that in a brand new color. So let's do it in green, so treatment. Now there are some medications that can be used. One class of drugs that's often used to treat individuals that have patent ductus arteriosus is called NSAIDS and what that stands for is nonsteroidal anti-inflammatory drugs and what that does is it inhibits prostaglandins. All right, so we have an inhibitory effect to these prostaglandins, reducing their levels, and that is gonna cause it to close. And then we can have some surgical treatments and there are two main types. The first one is gonna be called PDA ligation. What we're basically doing in that case is we're gonna tie this off at the beginning and at the end and by tying it off you're cutting off the blood supply here and then that's eventually gonna deteriorate. The second option is what we call coil occlusion and with that, it's kind of the similar principle, but we're using a different system. So what we're gonna do there is we're literally gonna insert a coil through that ductus arteriosus that blocks the blood flow and then that is gonna cause it to be occluded or stopped up so that blood cannot travel through and that, in effect, eliminates the problem of blood leaving through that ductus arteriosus. So those are the ways that it can be treated. We either target the prostaglandins or we try to surgically close the ductus arteriosus off.