Heart disease and stroke
Strokes Basics of strokes
- You've probably heard of
- people having a stroke,
- and you're probably familiar with the notion
- that it has something to do
- with the brain, and you'd be right.
- In particular, it's a rapid loss of
- brain function because of
- something strange happening
- with the blood flow to the brain.
- And let me show you that
- in a little bit more detail.
- And to do that,
- let's think about
- the 2 major types of strokes.
- There's the ischemic strokes,
- and the other type of stroke
- is hemorrhagic,
- and these can kind of be sub-categorized,
- but I won't go into all of the details there.
- And if I really just define
- ischemia and hemorrhaging to you,
- I think you'll have an idea
- of how these strokes are different
- and how they interrupt the blood flow
- to different parts of the brain.
- You know from the videos on
- stenosis and ischemia
- and the videos on heart attacks
- that ischemia is
- a lack of blood flow
- to certain body tissues.
- So an ischemic stroke is actually
- very, very similar to what we saw
- in a heart attack,
- except it's not occurring
- in a coronary blood vessel,
- it's occurring in a blood vessel
- in the brain.
- So let me draw that right over here.
- Let's say that this is
- a blood vessel in the brain.
- And let's say that blood is flowing
- in that direction (this is an artery).
- And so you could imagine
- that maybe there is a big blood clot
- that forms in some part of the brain.
- Let me do the blood clot in magenta.
- This blood clot might form because --
- no, that's not magenta --
- the blood clot might form
- because maybe there's a plaque there,
- maybe the plaque got ruptured,
- either way, this clot is restricting
- the flow of blood.
- And we know that this blood clot --
- we can call this a thrombus,
- or we could say that thrombosis
- has occurred over here--
- either way, the blood flow is restricted,
- and the brain tissue that's further downstream
- is not going to get its oxygen,
- and it might die; it might experience infarction.
- And that's why ischemic strokes are also
- sometimes called cerebral infarctions.
- These are all very fancy words,
- but I think, hopefully, they're becoming
- a little bit more common in our vocabulary,
- they keep showing up over and over again.
- And I also want to be clear:
- most strokes are actually
- ischemic strokes.
- The numbers I looked up, they say,
- 87% of strokes are ischemic.
- Now, the other type of way
- that you could have ischemia
- in one of these blood vessels,
- and this is completely analogous
- to what we saw in the heart,
- when we had heart attacks, is:
- you could have thrombosis,
- or you could also have an embolism.
- Whenever someone says thrombosis,
- or a thrombus, or thrombi,
- they're talking about blood clots.
- Whenever someone talks about
- an embolus, or emboli, or embolism,
- they're talking about something
- moving through the blood
- that eventually blocks a blood vessel.
- So you can actually have
- a thromboembolism,
- you can actually have a blood clot
- that gets broken off --
- so let me ignore this for now--
- let me paint over it a little bit
- so that this isn't the main cause of blockage--
- but you could actually have a blood clot
- that breaks off, becomes an embolus,
- and since it's an embolus due to a blood clot,
- you call it a thrombembolus --
- I always have trouble saying all of these words--
- and eventually it blocks an artery over here.
- So this right here is an embolism,
- but either way, you're blocking the blood flow
- further down the brain,
- [which] could cause infarction,
- that brain tissue will die,
- and whatever that brain tissue did
- for mental function, or whatever,
- is going to make it very hard
- for this person who is experiencing this stroke
- to do those things.
- Now, it's not always noticeable,
- that's called a silent stroke,
- but damage is occurring.
- The person experiencing the stroke--
- and I'm not a doctor,
- so take all of this with a grain of salt--
- the person experiencing the stroke
- could be anywhere from -
- well, one, they may not even notice
- that damage is occurring,
- they might have a headache,
- or it might be more severe,
- they might actually
- not be able to properly move
- a side of their body,
- or a side of their face,
- or properly be able to speak,
- so it really depends on what
- part of the brain is being damaged.
- But in either of these situations,
- an ischemic stroke is caused by
- some type of restriction or blockage
- that causes things downstream to not
- get proper oxygen, and then,
- so you can imagine,
- cells over here aren't going
- to get their oxygen,
- and then they might actually die.
- A hemorrhagic stroke -
- to hemorrhage means to bleed,
- it's literally just a fancy word for bleeding-
- and so in a hemorrhagic stroke
- you have a situation where a blood vessel
- can actually break, where you have a blood vessel-
- I'm actually trying to draw
- the same blood vessel- where it actually breaks.
- We'll talk more in the future
- of why a blood vessel might break -
- strongly related to high blood pressure
- and other risk factors,
- but I don't want to get into that right now -
- but you could imagine if a blood vessel breaks,
- you have all this blood spewing into the brain
- in, kind of, an uncontrolled way.
- So let's say this little diagram
- [that] I drew right here,
- that part of the brain,
- if you have a hemorrhagic stroke,
- you have all of this blood
- that's flowing into the brain,
- and all of that uncontrolled blood
- will mess up that part of the brain,
- that causes those neurons
- and brain tissue to malfunction
- and maybe causes some of them to die,
- and it would also cause
- the blood flow further dowstream
- to be impaired, so the stuff
- downstream aren't going to get
- the blood they need
- because all the blood
- is being released everywhere else.
- And since 87% of strokes are ischemic strokes,
- the remainder are hemorrhagic,
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