What is coronary artery disease? | Circulatory System and Disease | NCLEX-RN | Khan Academy

Aug 18, 2023

What is coronary artery disease? | Circulatory System and Disease | NCLEX-RN | Khan Academy

Created by Vishal Punwani.

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Content

1.443 -> - So you got your heart, right,

3.04 -> and so your heart is sitting in your chest

5.06 -> and it's this muscular pump that will

7.92 -> pump blood throughout your body.

10.34 -> So it needs to pump blood to all the places in your body.

13.6 -> And it actually does a lot of work.

15.6 -> It pumps about 100,000 times a day.

19.12 -> I'm not making that number up.

20.28 -> It actually pumps, if you take the average heart rate

23.6 -> which is about 72 beats a minute and then you

25.8 -> multiply that through for a day,

28 -> that ends up being about 103,000 beats per day, right.

33.1 -> So it's this really hard working muscle,

35.12 -> this really hard working organ.

36.96 -> And what do hard working muscles need?

39.22 -> Well, just think about the last time you went on a run,

41.94 -> or climbed a fence, or did a back flip,

44.7 -> or whatever it is that you do to get your muscles working.

47.42 -> They need a lot of oxygen, right?

49.44 -> What did you feel after you did all this exercise?

52.72 -> I mean you were probably gasping for air, you were panting,

55.12 -> at least you were breathing heavier, right?

58.22 -> And the reason for that is because your muscles,

61.18 -> you've used them, you've exhausted them a bit,

63.32 -> and now you have to pay back oxygen, right.

66.12 -> You have to give them oxygen.

67.82 -> Your heart is really no different.

69.701 -> You might be thinking, well the heart is getting

71.676 -> access to all of the blood that it pumps out, right,

74.036 -> so doesn't it just get, like, basically

76.076 -> an unlimited supply of oxygen from that?

78.176 -> From that blood?

79.316 -> Well, it doesn't actually.

81.596 -> So let me actually draw this for you in cross section.

84.056 -> So we're going to take a section through here

86.236 -> and we'll blow it up right here,

88.396 -> and you can kind of see right here

90.256 -> that the walls are pretty thick.

92.516 -> And so the oxygen in the blood flowing inside the heart,

95.856 -> it can't actually reach all the way across

98.296 -> the thick heart muscle wall.

100.956 -> It might be able to get to a little bit

102.436 -> of the inner section of the wall,

104.116 -> but it can't diffuse across the whole heart muscle wall

107.116 -> because it's just too thick.

108.832 -> So we have a solution for that, actually,

111.896 -> and this solution is the coronary arteries.

114.456 -> And the coronary arteries run on the outside of the heart.

116.956 -> So here's a heart, you can see this person's

118.336 -> right coronary artery and you can see this

120.856 -> person's left coronary artery, right?

123.156 -> Actually this is actually the left anterior descending

126.276 -> artery, which is a branch of the left coronary artery.

129.136 -> So, again, these coronary arteries are the solution right?

132.016 -> Where they bring copious amounts of blood

134.076 -> to the heart muscle and they feed it enough

137.236 -> blood to do all the work that the heart needs to do.

140.296 -> But sometimes they can get diseased, and so

142.276 -> coronary artery disease is one of the problems

145.016 -> that can go wrong with the coronary vessels.

148.836 -> So you may have heard the term "clogged arteries"

151.616 -> to describe coronary artery disease.

154.939 -> And why they're called clogged arteries is because

157.547 -> there's this build up of fatty substances

160.447 -> that's almost like plumbing being clogged.

163.467 -> So let's actually draw this out.

165.067 -> So here is, here's a close up of the coronary vessel right,

169.167 -> so we have one wall there and the other wall here.

173.19 -> So here's your blood, and here's

175.656 -> some components of your blood.

176.996 -> So you've got your red blood cells,

179.356 -> and here's some cholesterol,

180.796 -> and here's some white blood cells,

183.296 -> and when the cholesterol is sort of

185.956 -> flowing through your blood, and it comes across

188.456 -> a bit of damaged blood vessel wall, the cholesterol thinks

191.676 -> "Hey that looks like a pretty cool spot to hang out."

194.916 -> And so the cholesterol actually will start to

197.109 -> deposit inside the walls, inside the

199.529 -> damaged walls of your blood vessels.

201.869 -> And the white blood cells don't really like this,

204.549 -> so the white blood cells try to follow

206.709 -> in after the cholesterol to get rid of them.

209.389 -> To get them out of the wall.

210.489 -> And that kicks off this big inflammatory process

213.449 -> called Atherosclerosis.

216.189 -> And that just means hardening of the blood vessel,

218.489 -> because this whole process over time

220.469 -> makes that blood vessel wall become hard and stiff.

224.049 -> And unfortunately, during the process,

225.809 -> a lot of the white blood cells die.

228.449 -> So the cholesterol can just keep depositing in there,

231.109 -> and the cholesterol and the white blood cells

233.709 -> create this fatty bulge called a plaque, and over time

239.209 -> the plaque will start to bulge into the vessel.

242.049 -> Why is that a problem?

244.089 -> Well, I mean, blood needs to get through right?

246.029 -> If you've got this big bulge in the way

248.229 -> how is blood going to get through?

250.289 -> So for the first little while, I mean, blood can

252.672 -> through and you won't have any problems.

255.092 -> But over time, and I mean this plaque takes decades

259.971 -> for it to build up to clinically significant level.

263.692 -> And that means when you start to get symptoms.

265.972 -> So over time it'll just continue to grow,

269.172 -> and then you'll start running into some problems.

271.772 -> So, again, just to be perfectly clear,

273.852 -> coronary artery disease is when you start

275.832 -> to get buildup of this plaque, this fatty substance

278.492 -> within the arteries of your heart.

281.632 -> Let me just make some room here.

283.232 -> And why it's bad, why coronary artery disease is bad,

286.792 -> is because downstream, later in your life,

289.132 -> it can lead to some other heart diseases.

292.092 -> So we'll just briefly describe the main ones.

295.672 -> And we'll start with one you may have heard about before.

297.832 -> We'll start with stable angina.

299.972 -> So let's look at this bit of muscle down here

302.192 -> that the artery's sending blood to.

305.454 -> And let's put our plaque here,

307.189 -> let's say our plaque is here upstream.

309.149 -> When you're at rest,

310.269 -> when your heart's not doing too much work,

312.089 -> enough blood can get past that plaque

314.429 -> and get down and feed that muscle.

317.349 -> So that muscle's, you know, happy.

319.249 -> It's getting enough oxygen from the blood that's

322.269 -> getting to it and it's not feeling any adverse affects.

325.569 -> It's totally happy, all right?

327.069 -> But what happens when you start to, you know,

329.849 -> maybe you're going to miss your bus,

331.469 -> you need to run for your bus, or

332.969 -> you really want to impress that girl

335.589 -> so you start taking dance classes.

337.829 -> When you ask your heart to do more work,

341.569 -> you know your heart rate's going to go up

343.349 -> your heart's going to beat a bit faster.

344.949 -> Then all of a sudden not enough blood is going to be able

348.349 -> to get past that plaque and feed that muscle, right?

351.909 -> And so that piece of muscle becomes hypoxic.

355.949 -> When that muscle down there gets hypoxic

358.029 -> when it doesn't have enough oxygen

359.629 -> to carry out its function,

360.869 -> you start to actually get a symptom called angina pectoris.

368.309 -> What angina pectoris refers to,

369.949 -> let's actually just look at the two words.

371.609 -> So you've got angina, right,

373.549 -> and angina is from the Greek word "to strangle" right.

377.809 -> I know it sounds weird, but people describe

381.425 -> the feeling of angina as sort of a

383.413 -> tight, strangling, feeling in their chest.

387.333 -> Pectoris refers to "chest."

389.713 -> So angina pectoris is this tight strangling

393.113 -> feeling in your chest that is brought on

395.713 -> when your heart muscle doesn't have enough oxygen.

399.053 -> This is reproducable, this is reproducable.

401.62 -> So if you sort of lower your activity level,

403.8 -> if you stop that amazing dance move I'm sure you're doing,

407.38 -> or if you stop running for the bus,

408.96 -> and you sort of take a breather,

410.64 -> then your heart your essentially

413.6 -> asking your heart to do less work.

415.18 -> Right?

415.94 -> And when your heart is doing less work it needs less oxygen.

419.56 -> And so all of a sudden that blood

421.4 -> that is getting past that plaque

423.06 -> is enough to supply that downstream

425.44 -> bit of muscle again, right?

427.36 -> So the symptom of angina goes away.

430.42 -> The chest pain goes away because

432.32 -> your heart muscle's getting all of the

435.36 -> oxygen that it needs again, okay?

437.9 -> So the reason that it's called stable angina,

440.504 -> remember this overarching condition is called stable angina,

443.904 -> and the reason it's called stable angina

445.364 -> is because you can bring on,

447.844 -> you can predictably bring on the chest pain when you ask

450.944 -> your heart muscle to do too much work.

453.424 -> Exercise or exertion is gonna cause it,

455.684 -> and rest is gonna relieve it.

457.584 -> Now, things can get a little bit worse than that.

461.816 -> And when they get worse than that,

463.836 -> they can result in a suite of, not sweet as in

467.516 -> sweet "I want that" 'cause you definitely don't want this,

470.236 -> but it refers to a set of conditions, diseases, you can get

475.956 -> called acute coronary syndrome.

479.036 -> And acute coronary syndromes they can be further sub divided

482.376 -> into something called unstable angina.

485.416 -> Let's make some more room.

487.556 -> So you can imagine already, because you know

489.556 -> what stable angina is, you can kind of imagine

491.416 -> what unstable angina is.

492.716 -> You've got unstable angina, and then

495.476 -> you have your heart attacks.

497.962 -> So unstable angina, just to be clear again,

500.696 -> stable angina, not a heart attack.

502.956 -> Unstable angina, not a heart attack.

505.296 -> Heart attack, is a heart attack.

507.656 -> Go figure.

508.516 -> So let's look at unstable angina first

510.916 -> before we look at heart attacks.

512.635 -> Unstable angina is, remember that plaque we talked about,

515.736 -> let's go back to our nice little blood vessel here,

517.556 -> well it's not nice any more,

518.534 -> it's got a huge honking fatty plaque in it.

520.576 -> But that's all right.

521.456 -> So here's our blood vessel, right, here's our plaque.

525.092 -> Now sometimes, because of whether it's

527.953 -> hypertension putting sheer stress on this plaque,

532.113 -> or whether it's spontaneous, this can happen spontaneously,

535.813 -> you know there'a couple other reasons but those are

537.713 -> probably the two major reasons,

539.793 -> the plaque can rupture, right.

542.993 -> And when I say rupture, I mean that this

545.593 -> covering of the plaque on the inside of the blood vessel

549.653 -> can kind of burst, right, and when it

553.27 -> bursts it exposes all the plaque material

556.89 -> all that fatty gross sort of necrotic,

559.81 -> necrotic means dead cells by the way

562.27 -> because the cells in here have some of them

564.942 -> are dead at this point,

566.083 -> it exposes them to the blood, right.

568.903 -> And plaque material is really thrombogenic.

573.623 -> What does thromogenic mean?

574.963 -> Thrombogenic means it causes blood clots to form on it.

579.183 -> And let me just re-draw this, it's a little messy.

582.758 -> So when the blood sees that plaque material

586.02 -> it's going to go crazy.

587.42 -> You've got your platelets in your blood,

589.44 -> and you have your clotting factors in your blood,

591.78 -> and they're all going to grab onto that

593.2 -> ruptured plaque material.

596.02 -> You're going to start to form a clot, a blood clot,

600 -> on this ruptured plaque.

602.1 -> And from here, one of two things can happen.

605.04 -> Either this ruptured plaque can start to

607.64 -> sort of flap back and forth, because it's

611.24 -> ruptured on this end, but it might

612.76 -> still be attached on that end.

614.26 -> So what does this mean?

615.14 -> That means that you're gonna get, sometimes,

617.06 -> your blood vessel's gonna be completely

619.78 -> occluded, it's gonna be completely blocked off,

621.7 -> and sometimes you're not gonna have

624 -> an occluded blood vessel because the

625.66 -> plaque will be kind of stuck against the wall again.

627.7 -> It's sort of flapping around there

629.1 -> in your blood vessel as blood goes by, okay.

631.947 -> And so remember what we said earlier

634.3 -> if we deprive downstream parts of the heart

636.46 -> of blood, you start to get that hypoxia happening and

640.36 -> you start to get that chest pain, that angina, happening.

643.54 -> But remember, now we have this plaque flapping around.

648.575 -> So at any point you could just loose

651.335 -> blood supply to a downstream part of your heart temporarily.

655.095 -> And so in this condition, unstable angina,

658.255 -> you can get chest pain at rest.

661.215 -> You don't actually have to exert yourself

662.815 -> for chest pain to come on, right.

665.795 -> And that's because it's just flapping around there.

668.355 -> It can happen at any point.

669.495 -> So that's why we call it unstable angina,

672.075 -> because it's not predictable and it can

674.235 -> really just happen any time.

675.953 -> So the last thing now we need to talk about,

677.733 -> that's part of acute coronary syndrome that's caused

681.353 -> by coronary artery disease, is heart attack .

685.573 -> Right?

686.213 -> And so remember we said that this ruptured plaque

689.793 -> is now exposed to the blood, and remember

692.013 -> the clotting factors have all started to clot onto it

694.373 -> well blood cells can join in, right, join the party,

697.553 -> and one of two things can happen.

699.733 -> Either the clot, also called a Thrombus by the way,

702.733 -> a clot is also caused a Thrombus,

704.613 -> can get so big that it completely blocks off

707.473 -> that blood vessel.

708.593 -> And that's also called Thrombosis.

711.153 -> To completely block off a blood vessel

713.173 -> by a clot is called Thrombosis.

715.253 -> Or it can break off, so this clot, this Thrombus

720.593 -> can break off, also called embolization.

724.293 -> So when a bit of a Thrombus breaks off

726.013 -> it's called embolization.

727.193 -> So it can embolize and float downstream

730.762 -> and block off a smaller blood vessel.

732.949 -> So this is it floating downstream and

735.369 -> blocking off a smaller blood vessel, right?

738.189 -> So when either of those two things happen, that's when

742.758 -> you end up with something called a heart attack.

744.838 -> Right?

745.778 -> Because now, that's not going to resolve on it's own.

748.818 -> You've completely cut off oxygen

750.478 -> to a part of the heart.

751.598 -> And so the heart muscle that that

753.598 -> artery is supplying will die.

756.938 -> Because now it doesn't have it's supply of oxygen.

759.538 -> And, you know, if you actually get to a hospital

762.341 -> and you get either medication or

765.861 -> some type of surgical intervention

768.121 -> before about 20 minutes,

770.501 -> then you can save that bit of heart.

773.101 -> If that blockage, so either via complete Thrombus

775.941 -> so blockage of the artery, or embolization

779.461 -> and blockage of a downstream artery,

781.141 -> if that lasts for more than about 20 minutes,

784.441 -> then that heart muscle, that bit of heart muscle

786.461 -> will permanently die.

788.781 -> And that's what a heart attack is.

790.921 -> Now one more thing I want to clarify.

792.561 -> Heart attack is not the same thing as heart failure.

795.461 -> Heart failure is when your heart can't

798.421 -> pump enough blood to meet the needs of your body.

801.421 -> That's heart failure.

802.801 -> Right?

803.401 -> So heart attack is different.

804.461 -> A heart attack is when a piece of your heart muscle

807.201 -> actually dies because it itself

810.821 -> isn't receiving enough oxygen.

812.681 -> Okay?

813.741 -> That's the difference between

814.841 -> heart failure and heart attack.

815.841 -> Although they can actually cause each other to happen.

Source: https://www.youtube.com/watch?v=EATkbpqlxvc