What is heart failure? | Circulatory System and Disease | NCLEX-RN | Khan Academy

Aug 18, 2023

What is heart failure? | Circulatory System and Disease | NCLEX-RN | Khan Academy

Visit us (http://www.khanacademy.org/science/he…) for health and medicine content or (http://www.khanacademy.org/test-prep/…) for MCAT related content. These videos do not provide medical advice and are for informational purposes only. The videos are not intended to be a substitute for professional medical advice, diagnosis or treatment. Always seek the advice of a qualified health provider with any questions you may have regarding a medical condition. Never disregard professional medical advice or delay in seeking it because of something you have read or seen in any Khan Academy video. Created by Tanner Marshall.

Watch the next lesson: https://www.khanacademy.org/test-prep…

Missed the previous lesson? https://www.khanacademy.org/test-prep…

NCLEX-RN on Khan Academy: A collection of questions from content covered on the NCLEX-RN. These questions are available under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 United States License (available at http://creativecommons.org/licenses/b…

About Khan Academy: Khan Academy offers practice exercises, instructional videos, and a personalized learning dashboard that empower learners to study at their own pace in and outside of the classroom. We tackle math, science, computer programming, history, art history, economics, and more. Our math missions guide learners from kindergarten to calculus using state-of-the-art, adaptive technology that identifies strengths and learning gaps. We’ve also partnered with institutions like NASA, The Museum of Modern Art, The California Academy of Sciences, and MIT to offer specialized content.

For free. For everyone. Forever. #YouCanLearnAnything

Subscribe to Khan Academy’s NCLEX-RN channel: / @khanacademynclex-rn7898
Subscribe to Khan Academy: https://www.youtube.com/subscription_…

Content

2.32 -> - [Voiceover] So your heart pumps blood

3.4 -> essentially to two places

5.2 -> and the first place is your body.

6.8 -> So you have your oxygenated blood on the left side

9.3 -> and we gotta remember that the lefts

10.69 -> and the rights are switched because

12.148 -> we're looking at the anatomical view of the heart.

14.51 -> So it pumps it out to your body

15.52 -> and your body gets that oxygen.

17.83 -> Your body uses it up and then circulates it

19.65 -> back into the right side

21.71 -> where this time it's pumped out to the lungs

23.82 -> and gets re-oxygenated and gets that oxygen back

26.25 -> and then it's circulated back into the left side.

29.26 -> And the amount of blood at any time pumped

30.59 -> to your body is sort of based on this demand

33.5 -> that your body has for blood.

35.23 -> You can kind of think of it like you have this gage

37.1 -> that says, "Hey, I need this much blood

39.19 -> "to sustain this much activity."

41.395 -> And this can change,

42.435 -> so if you start working out or something,

44.175 -> your demands might go up

45.975 -> and your heart can accommodate for that

47.165 -> and start pumping more blood to that body

49.295 -> to meet those new demands.

52.015 -> Heart failure describes this condition

54.045 -> where the heart can't meet the demands of the body.

56.475 -> So at any given time, the heart's not able

58.505 -> to pump enough blood to meet the body's demands.

63.725 -> And there are essentially two types of heart failure.

67.065 -> The first one we call systolic heart failure

70.025 -> and systolic refers to systoli,

72.325 -> which is the phase of the cardiac cycle

73.935 -> where blood is pumped out of the heart

75.735 -> and so systolic heart failure is

78.205 -> when those heart muscles aren't pumping blood

80.035 -> with enough force.

82.505 -> So this often means that those muscles are weakened

84.515 -> and smaller than with a healthy heart

86.805 -> and this typically makes it look quite a bit different.

90.115 -> And when these smaller muscles contract,

91.955 -> they don't squeeze as hard as they used to

93.877 -> and this causes less blood to be ejected

96.165 -> with each contraction.

98.355 -> Now, I say contraction

99.225 -> because the heart's this muscle, right?

101.195 -> So, when it contracts,

103.025 -> it squeezes.

104.555 -> You can kind of think of it like you have

106.025 -> this water bottle that you're holding with your hand

108.155 -> and you squeeze the water bottle

109.495 -> and it shoots the water out.

111.035 -> It's the same concept with your heart.

112.605 -> When those muscles contract,

113.845 -> they squeeze the blood and that's

115.495 -> how you eject blood to both your body and your lungs.

119.075 -> With systolic heart failure,

120.475 -> since your heart muscles are smaller,

122.715 -> think about squeezing that water bottle again,

124.515 -> but just pinching it.

126.045 -> It's gonna be a lot harder to squeeze the water out, right?

128.555 -> Well, it's the same thing for the heart

130.225 -> with smaller and weaker muscles.

131.785 -> It's gonna be way harder for it to squeeze

133.585 -> and pump that blood out to the body.

138.295 -> You probably noticed that this heart has

139.825 -> these sort of enlarged looking lower chambers

142.938 -> and at the same time, it has this really thin muscle wall

146.405 -> and these are really characteristic traits

148.415 -> of a heart with systolic failure.

150.405 -> And these small muscles make it really hard

152.645 -> for it to pump blood to the body.

156.115 -> So that was the first type of heart failure.

158.515 -> The second type is called diastolic heart failure

161.525 -> and instead of being a pumping problem

163.055 -> with the muscles being too small,

164.695 -> diastolic failure is a filling problem

168.165 -> which is why we call it diastolic failure,

170.265 -> because it refers to diastoli

172.405 -> which is that phase in the cardiac cycle

174.435 -> where the heart fills with blood.

176.958 -> So with this type of failure,

178.965 -> your body's not receiving enough blood

180.165 -> because your heart's not filling with enough blood

182.175 -> to pump out in the first place.

185.105 -> So if we jump back to that water bottle analogy,

187.605 -> this time you're holding it with one hand,

189.575 -> just like we were for the healthy heart,

191.675 -> but instead the bottle's filled with less water,

194.115 -> so even if you squeeze it with the same force

195.685 -> as a healthy heart, less water is gonna be ejected

198.265 -> simply because there's less water in the bottle.

201.725 -> And this is essentially what's happening

203.165 -> with diastolic failure.

204.825 -> Since there's less blood filling in the ventricles,

206.895 -> even if it's pumping with the same force,

208.905 -> less blood's gonna be ejected to the body.

212.305 -> But why is there less blood filling in the chambers?

214.145 -> Well, it's because those muscles

216.575 -> are actually larger in this case

217.875 -> and they take up more space

219.915 -> and this leaves less space for that blood

221.715 -> to fill in to the ventricles.

225.325 -> Okay, so far we've shown both types of heart failure

228.245 -> and each time we've shown it happening on both sides.

231.225 -> Well, this isn't always the case.

232.795 -> It's definitely possible to have isolated heart failure.

236.325 -> So maybe you only have the left side

239.405 -> or maybe you might only have it isolated to the right side.

244.465 -> One important thing to not though is

246.175 -> that usually a left-sided case happens first

248.505 -> and then that ends up leading to a right side failure.

253.085 -> I know I'm only showing systolic failure here,

254.945 -> but I should not that this isolated failure

257.715 -> can happen with either systolic or diastolic.

261.955 -> So, depending on which side this is happening on,

263.915 -> the left or the right,

265.465 -> the symptoms are gonna be a little different.

267.465 -> Let's just go ahead and start with the left side first.

270.404 -> So since the left side pumps blood out to the body,

272.335 -> that means it's coming in from the lungs

275.765 -> and if it's not pumping it very efficiently to the body,

278.135 -> that blood starts to get backed up into the lungs.

281.635 -> Think of it like a traffic jam.

283.675 -> What happens when they close a lane

284.945 -> and then they only let one car through at a time?

287.505 -> All those other cars get backed up.

289.915 -> It's kind of the same thing.

291.385 -> This blood gets backed up into the lungs

292.945 -> because it's only pumping a little bit out at a time now.

296.025 -> So a really common symptom of left-sided heart failure

298.225 -> is fluid build up in the lungs.

301.025 -> This is called congestion

302.325 -> and it's also sometimes why we say congestive heart failure.

306.995 -> Alright, so that was left-sided failure.

309.105 -> Let's take a look at right-sided failure.

311.005 -> Again, I'm just gonna show systolic failure,

313.225 -> but let's just note that this can either happen

314.845 -> with systolic or diastolic.

317.945 -> This time, since we know that the right side

319.275 -> pumps blood to your lungs,

320.945 -> we also know that it comes from the body.

324.575 -> And since it doesn't pump blood as well to the lungs,

326.885 -> we have that traffic jam situation again,

328.955 -> but this time it gets backed up into the body.

332.555 -> So patients with right-sided failure might start

334.225 -> getting fluid build up in their feet, legs and abdomen.

337.995 -> And again, just like the left side,

339.235 -> you have congestion or fluid build up,

341.105 -> but this time it's in your body instead of your lungs.

345.305 -> So as a quick recap, you could just have systolic failure

348.165 -> on the right side or you could just have

350.267 -> systolic failure on the left side

352.837 -> and it's possible to have both.

354.777 -> In the same way, you can have diastolic

356.347 -> on the right side only

357.747 -> or you could have it only on the left side.

361.787 -> Or you might have both.

364.127 -> It's even possible to have a combination

365.857 -> of systolic and diastolic failure.

369.077 -> So now that we've kind of nailed those down,

371.557 -> let's talk about this really important way

374.127 -> that we measure the heart's ability

375.557 -> to meet the demands of the body

377.467 -> and that's called cardiac output.

379.707 -> Cardiac output represents the total amount of blood

382.107 -> that the heart's able to pump every minute,

384.737 -> usually given in liters of blood per minute.

387.377 -> And the normal cardiac output is

388.647 -> around five liters per minute.

390.63 -> Now, cardiac output can be broken down

392.247 -> into two other components

394.317 -> and the first is stroke volume

396.107 -> which is the amount of blood pumped out every beat

398.367 -> which is different than cardiac output

400.187 -> because it's every beat, not every minute

402.937 -> and so we take this stroke volume

404.157 -> and we multiply it by your heart rate,

406.187 -> which is measured in beats per minute

409.027 -> and those two multiplied together

410.167 -> equals your cardiac output.

412.407 -> So if you were to change either stroke volume or heart rate,

416.447 -> for example, let's say I lowered stroke volume,

419.547 -> since cardiac output's dependent on these two variables,

421.877 -> cardiac output's also gonna go down

424.247 -> and that's what happens with heart failure.

425.887 -> Cardiac output is lower because the heart's

427.687 -> not pumping as much blood per minute.

430.293 -> This is usually because there's a lowered stroke volume

432.932 -> or a lowered amount of blood pumped out

434.547 -> with each contraction.

436.757 -> So usually heart failure is considered a secondary disease,

440.527 -> meaning that it's caused by some kind of pre-existing

443.467 -> or underlying disease that already affects cardiac output.

446.797 -> Specifically, we're gonna think about diseases

448.377 -> that cause the death of cardiac muscle cells

451.437 -> which are also called cardiomyoctes.

453.907 -> And when those muscle cells die,

455.547 -> the heart gets weaker and gets way worse at pumping blood.

458.667 -> This lowers stroke volume

459.877 -> and then it also lowers your cardiac output.

463.047 -> And when the cardiac output goes down,

464.627 -> the heart has two options to increase it again.

466.487 -> Based on our equation, that's stroke volume and heart rate.

470.487 -> And your heart actually does that

471.657 -> and this is called compensation.

473.427 -> So your heart compensates by either squeezing harder

476.097 -> and increasing stroke volume,

477.467 -> or beating faster and increasing heart rate.

481.877 -> In the early stages of heart failure

483.377 -> these methods can actually help quite a bit

485.237 -> in compensating for decreased supply,

487.777 -> but over time those surviving muscle cells

490.017 -> become overworked because they're constantly trying

492.547 -> to either beat faster or squeeze harder.

495.857 -> But to do either of those things,

497.187 -> those cells need more oxygen.

499.297 -> This is the whole issue with heart failure

500.857 -> in the first place, a decreased supply of oxygen,

503.497 -> those muscle cells won't receive the oxygen

505.627 -> and more muscle cells tend to die off.

508.187 -> And when more die off, stroke volume goes down even more

512.057 -> and this causes this whole cycle to repeat

513.797 -> which causes heart failure to get worse.

Source: https://www.youtube.com/watch?v=2aiRpr5UCZs