Atrial septal defect | Circulatory System and Disease | NCLEX-RN | Khan Academy
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Atrial septal defect | Circulatory System and Disease | NCLEX-RN | Khan Academy


Lecturer: I wanna talk about
a condition that is called atrial septal defect and, you know, that might sound a bit complicated
but it really isn’t. Let’s break it down one step at a time. A atrial, of course,
we’re dealing there with the right and left atria
so that’s the first word. Septal. A septum is a wall and we have a wall right here in between the left and right atria so that makes sense too. And if we have a defect,
we have some type of a structural abnormality and
with atrial septal defects what we are usually dealing
with is a whole in the wall. So we have a hole, which is a defect, in the wall, which is the septum, and it’s gonna be between the left and right atria. So it all makes sense. So ever here we have our right atrium, over here with have our
left atrium and, of course, we have our right ventricle
and left ventricle. We’re not gonna focus
on those in this video but I just want to
mention that really quick. Alright, so. If we have a hole in the wall between the left and the right atria, what’s gonna happen? Well, this left side of the
heart is doing a lot of work. It’s sending blood all
throughout the body, literally all throughout the
body, it’s going, you know, in this direction, it’s going to the head, it’s going to the upper
extremities and then it’s also going down to
the lower extremities. It’s going everywhere so this side is gonna be significantly
stronger than this side. Significantly higher pressure on the left than we have on the right. Because the right, where are we going? Well, it’s taking this deoxygenated blood and it’s going to our lungs. The lungs are right here, let me draw in a lung
right here really quick. So this is my lung. It’s not far. It’s not a huge distance it has to travel. So we have lower pressure
on the right side. So as a result, of that, what we’re gonna end up in an individual
with an atrial septal defect is we’re gonna have
blood kinda squeezing in through that opening, and going from the left atrium to the right atrium. And of course, if you have
some blood squeezing there, it’s gonna continue on the
path that it normally travels and it’s gonna go back to your lungs. Now, in terms of the positioning, most times we have the
atrial septal defect kind of right here in the middle. And that has to do with the fact that when you look at the
heart, when it’s developing in the embryo, this wall
isn’t there in the beginning. But when it comes there is an opening that allows for blood
when it comes back from the placenta because it’s getting oxygen from the mother, that’s
gonna bypass the lungs because the lungs aren’t functioning as yet in that developing embryo. So it’s gonna bypass
the lungs and one of the ways it does that is by
going through this opening. So if that opening fails to close, it’s suppose to close,
we want it to close, and that closes soon after birth. But if it fails to close, we can get an atrial septal defect and this positioning is called “ostium secundum.” Alright, so that’s the position, that’s the place where we usually have it. Right there in the middle of the wall and that is considered ostium secundum. But it can also be lower down. So if we were to have a hole down here. Let’s make sure I have that selected. So if we have a hole down here, to the point that maybe it even involves this valve between the
atrium and the ventricle, well what that is considered to be is. Let’s draw that over here. Let me do it in a different
color just to be fancy. That is gonna be “ostium primum.” Alright, so that’s lower down. That’s not generally seen
but it is seen in individuals with, in some individuals,
with Down’s syndrome. This is gonna be the most common congenital heart defect, and congenital, it just means that
individual is born with it. But that’s gonna be the
most common congenital heart defect in people, in
babies with Down’s syndrome. So what are the signs? Well, it’s usually. Ok let’s just put over here “signs.” It’s usually asymptomatic. So number one, let’s
just put “asymptomatic.” And the reason for that is, ok, you have a hole in the heart. It sounds like a huge deal
but it’s not necessarily a huge deal because that’s
just get a little more of the oxygenated blood
going back to the lungs. But the oxygen levels are
still relatively fine. They’re adequate for normal function so we don’t generally have problems. But another thing that
we can see in individuals with atrial septal defect is what’s called a “paradoxical embolus.” Paradoxical embolus. And what that is, let’s say… Just draw this simply. This is somewhere in
the body and let’s say, here we have, since I’m
drawing a blood vessel I’m gonna draw the blood vessel in red. So here we have a blood vessel. Doesn’t matter what blood vessel it is. And this blood vessel is in the legs. And in that blood vessel, for some reason, we get a clot, there’s some kind of damage that causes a clot to form. As the blood is rushing through there, a piece of that clot might break off. And that clot can travel
back to the heart, going through the right
atrium and right ventricle and normally what can happen is that clot gets stuck in the lungs, and there we have a pulmonary embolism. But in individuals with
an atrial septal defect, that can potentially give
that clot or that embolis a different direction, a
different route to travel. Now, that’s usually not
gonna happen because of course, higher pressure
over here in the left pushing towards the right, so the
stuff isn’t necessarily going from the right atrium
to the right ventricle. But let’s say that individual is straining to do something and they’re baring down or let’s say even that
individual goes to the restroom and, you know, they go to take a poop. And when they go to
take a poop, of course, they’re applying a lot
of pressure and that applies pressure on this
side and if that increases above the left side, that can cause that clot to travel into the left side. And then via that left side,
it can go via these major vessels and possible even go to… This is a terrible attempt at a brain. And imagine if it’s
going to a blood vessel that’s going to the brain. What can that cause? Well, that can actually cause a stroke. So it’s not usually a
problem, but you can see how it can potentially
be a problem if there’s a clot that then travels
to the left atrium and then goes to the rest of the body. Possibly even going to the
brain and causing a stroke. Now, how these atrial septal defects are normally noticed, at least
at first, they’re noticed because when the baby is born, I remember when my son was born,
one of the first things they did is the nurse took a stethoscope and she listened to
the sound of the heart. And when she listened to
the sound of the heart fortunately, it sounded fine. But one of the ways
that you can detect this is when you listen to the sound, you hear something like,
what you’re suppose to hear. Lub, dub. So let’s say this
represents those two sounds, lub dub. Now this first sound is gonna represent the closing of the valves between the atria and the ventricle. So this valve right here between the left atrium and left ventricle. And then this valve over here between the right atrium and the right ventricle. That’s the “lub” sound. That this first sound that you hear. The “dub,” the “lub dub.” This second sound is gonna be because of the closure of two other valves. The two other valves would be this pulmonary valve here, going
into the pulmonary vessels. And this aortic valve
which leads, which the blood goes through to lead into the aorta. So this “dub” is the
closure of these two valves. Now, with an atrial septal
defect, what you have, because blood is gonna
be shunting from the left to the right, we’re
gonna get an increase in the amount of blood that’s
going to the right side, and because we get that
increase, we’re gonna get an increase in the
blood that’s going to the pulmonary circulation and
as a result of that, we’re going to get this valve closing just a little later than this valve. So what’s gonna end up
happening as a result if we look at this second sound. It’s gonna look a little different. Now this isn’t gonna be 100% accurate but it’s gonna illustrate the point. It’s gonna look a little different in that we are gonna split this second sound. So it’s no longer a “lub dub”
it’s a “lub durub, lub durub” because the pulmonary
valve is closing just a little later than the aortic valve, resulting in this split sound. So that’s pretty much what you get with a atrial septal defect. It is usually ostium secundum. It can be ostium primum,
especially in individuals with Down’s syndromes,
usually asymptomatic, sometimes resulting in
a paradoxical embolis, which can potentially lead to a stroke. And when you listen to
the sounds of the heart with a stethoscope, you
get this split S two.

About James Carlton

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84 thoughts on “Atrial septal defect | Circulatory System and Disease | NCLEX-RN | Khan Academy

  1. This video is very Informative!!
    I have two Q's: After doing ASD closure medical procedure, would ASD reoccur sometime in the future? 
    can the person lead a normal life?

  2. You are one the greatest instructors I am able to fully understand completely. Thank you for the vids, and hope to see more!

  3. I have a quick question my daughter is 3 yo and has a ASD with right sided hypertrophy. What level of risk is there for damage to the pulmonary system from the larger volume of blood being introduced to the system and increased pressure over time. 

  4. so, great video but please note (being a bit picky but since this is for learners) it's Down Syndrome, not Down's Syndrome.

  5. "and you know, they go to take a poop, and when they take a poop of course there is a lot of pressure…."

    Thanks for keeping things interesting.

  6. I was looking for the Dr. Najeeb lecture on CHD's (which is exceptionally good) and I couldn't find it so I watched this. I think you first need to cover the development aspect, at least the interatrial septum. You don't explain what the septum primum and secundum are but tell that if the defect is in middle it's a secundum defect! That's atrocious!

  7. I'm just coming across this studying for an exam in advanced pathophysiology as part of my studies to become a Family Nurse Practitioner. Your wonderful illustration and explanation helped me understand that the "split" sound is coming from the aortic valve closing before the pulmonic valve ( due to excess volume of blood). Thank you for this!

  8. why is it the second sound get split i mean why does the pulmonary valve get close late? is it because the high pressure became in the right side of the heart??? thanks for the amazing video n ur nice explaining

  9. I had atrial septal defect as a baby and they told my mom they would operate on me when i was 3. They said the hole was pretty big for a baby's heart but thankfully it closed and the doctor said it was a miracle. I am now 14 and have decided to be a pediatric cardiologist. Thanks to all the doctors out there😃

  10. My baby girl has congenital ASD, she is one year old now and she is doing well, but paediatric cardiologist recommends open heart surgery, I wonder what will happen if she doesn't go for surgery, mommy is not keen on surgery..

  11. Good for general population, but not complete enough for medical students. It's missing the explanation of how pulmonary hypertension occurs and how the left-> right blood flow changes to right->left after some time, which in turn opens the possibility for a paradoxical thromboembolism. You also need to include the embryology part and explain how the atrial septum is formed in the first place and how the foramen ovale is supposed to look and function, and how it functions in ASD, differences in pressures between right and left atrium, how they change as the defects progress, etc. That is all important to really understand what's going on.

  12. You explained it really well thanks for making it easy. Just a small correction it is actually Down Syndrome, not Down's.

  13. Thnku so much..I have exam tomorrow..Nd I never understood it. Bt today after watching video…I got my concepts clear…U r so good…😘😘😘thnkuuu

  14. Ostium secundum defect is created because of excessive muscular resorption or excessive programmed cell death (apoptosis) of the septum primum essentially leaving a bigger hole ( ostium secundum) that overlaps the septum secundum. Systemic vascular resistance is higher during birth which in normal circumstances the left atrial pressure increases and pushes septum primum and septum secundum together for an anatomical closure that eventually will lead to fusion of septum into one atrial septum. But because righ side of heart has lower pressure the blood leaks back from the left atrium to right atrium converting it from a physiological normal right to left shunt through the valves to left to right shunt through a hole. This eventually leads to a increase in blood volume as less blood is getting out of the heart, therefore it increases preload and end diastolic volume. This leads to an increase in presure and contraction force for the left ventricle to push blood out of heart. This can go into two directions the left ventricle hypertrofies to push out more blood or it dilates to the point of no return ( left heart failure). If left heart failure occurs the pulmonary trunk will begin to do excessive work till the point where pulmonary hypertension develops because of excessive blood volume and right heart hypetrophy or dilation begins to occur because pulmonary vascular resistance is higher than systemic vascular resistance leading in the end to a righ to left shunt later in life ( Eisenmenger syndrome).

  15. thank you for the explanation i understood now the problem that my child have. its ASD type ostium primun. but i dont know if is obligatory to correct this with sternotomy??????????

  16. Thanks for this!! I had a stroke 6 years ago and now I finally know how it happened. My mom drank when I was in utero, had a hole that went undetected until my stroke

  17. I have this an going to have surgery Wednesday. I am so scared. I have had a stroke and a heart attack. I have had chest discomfort for years . I was 23 when they found this. Now I am 37 with 2 kids.

  18. Beautiful explanation.. my nephew has 7-8 holes in his heart. He is jus 21days old.. doctors adviced for an open heart surgery.. we are really worried alot.. will he be ok?? If anyone had this type of situation pls rly

  19. This is what happened to me. I had a vein removed from my right leg, three days later I had a stroke. I don’t think the poop thing caused it, but it was devastating.

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