Complications after a heart attack (myocardial infarction) | NCLEX-RN | Khan Academy

Aug 26, 2023

Complications after a heart attack (myocardial infarction) | NCLEX-RN | Khan Academy

Created by Vishal Punwani.

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Content

1.933 -> - [Voiceover] After you've had a myocardial infarct,

4.429 -> a heart attack, you are prone to developing complications.

8.921 -> A complication in this sort of context

11.255 -> is essentially another disease or condition

13.983 -> that crops up as a result of your myocardial infarct.

18.395 -> Most complications tend to occur

19.974 -> within the first few weeks after having a heart attack,

24.095 -> so let's look at some of the major complications

26.208 -> that can occur after myocardial infarct,

29.726 -> and let's sort of do this in a step wise fashion

31.711 -> to make everything sort of flow logically in our heads.

34.787 -> We can say that myocardial infarcts

36.355 -> cause three major problems with our hearts, right?

39.199 -> So, one of the things is they cause our heart

41.649 -> to have decreased contractility, because

44.853 -> after a heart attack, you've sustained some damage

47.581 -> to your heart muscle, so it can't always contract very well.

52.248 -> You also get this electrical instability in your heart

55.708 -> because all of the ions that sort of move back and forth

58.413 -> across your heart muscle cell membranes

61.036 -> to maintain your electrical gradients, or your heartbeats,

63.926 -> properly, they all get really disrupted

66.864 -> so you have this electrical instability.

70.231 -> You also get tissue necrosis, right?

72.216 -> You get death of some of your heart muscle cells.

76.256 -> These three sort of effects of having a myocardial infarct,

79.623 -> they really underly all of the downstream complications

82.676 -> that are possibly going to crop up.

85.114 -> So how does reduced contractility do that?

87.332 -> Well, if your heart's not contracting properly,

89.805 -> then you're not going to effectively be able

91.813 -> to push blood out of your left ventricle

93.903 -> to the rest of your body, right?

96.097 -> So you end up in a state called hypotension

99.127 -> and hypotension just means that you have

100.636 -> pathologically low blood pressure.

103.887 -> When you have pathologically low blood pressure,

105.826 -> you're not going to be able to fill your coronary arteries

108.507 -> with enough blood, all the blood that they need.

111.178 -> Remember, besides the coronary artery

112.931 -> that's been blocked to result in your myocardial infarct,

116.251 -> there are still other coronary vessels that needs to have

118.712 -> a healthy supply of blood coming to them

120.825 -> so that they can in turn supply blood

123.1 -> to the rest of your heart muscle, right?

124.83 -> The heart muscle that isn't infarcted.

127.395 -> So if they're not getting enough blood,

128.882 -> then you'll start to get ischemia in the muscle

131.146 -> and other parts of your heart.

133.212 -> If you get ischemia in other parts of your heart,

135.244 -> then that will cause more of your heart muscle all over

137.868 -> to not contract properly

140.573 -> and eventually, you might not be able

141.965 -> to maintain your cardiac output at all

144.601 -> and end up in a condition called cardiogenic shock

148.002 -> and because this wall here, and we're assuming

150.023 -> that it's this wall that's been sort of

151.474 -> injured in the heart attack,

153.482 -> because this wall isn't contracting very well,

156.571 -> you'd be predisposed to forming a thrombus, a clot,

159.577 -> on the inside of that left ventricle there,

161.969 -> because when blood isn't constantly moved around

164.465 -> as it might not be in that little area there,

166.404 -> it tends to clot

168.389 -> and why is that bad?

169.689 -> Well, sometimes they can kind of flick off,

171.396 -> become separated off of the left ventricle wall there

174.53 -> and travel through the aorta

176.237 -> and into other vessels of the body

178.082 -> where they might get stuck

179.569 -> and cause an infarction in another part of the body.

182.088 -> For example, if one went up into your brain,

184.99 -> it might get stuck in one of your cerebral vessels

188.299 -> and cause a stroke, so embolism is a potential problem.

191.817 -> Embolism is the mobilization of a thrombus, a clot.

196.019 -> Alright, what about this electrical instability over here?

199.305 -> Well, the electrical instability can cause arrhythmias,

202.741 -> which is when your heart doesn't beat with a normal,

204.728 -> regular rhythm like it's supposed to.

207.712 -> Again, that's due to a combination of things.

209.593 -> That's due to sort of disorganized ion movement

214.155 -> within the cardiomyocytes, and it could also be due to

217.417 -> a disrupted electrical conduction system within the heart.

222.386 -> I should mention, as part of this

223.814 -> conduction system compromization here

226.995 -> the two major pace maker centers in your heart

229.851 -> are located in your right atrium,

232.092 -> so you've got your sinoatrial node about there

235.354 -> and you have your atrioventricular node around here

239.046 -> and these two nodes are really responsible

241.031 -> for regulating the normal rhythm of your heart

244.827 -> and so if you happen to have a myocardial infarct

247.544 -> that affected the right atrium, where both these nodes live,

251.398 -> you would probably end up developing an arythmia

254.219 -> because you'd potentially knock out

255.694 -> the two biggest regulators of your heart beat,

258.339 -> your heart rate and rhythm.

260.325 -> Alright, what about this tissue necrosis thing?

263.472 -> Well, remember, necrosis just refers to death of something

266.676 -> so in this case, death of the heart tissue.

270.136 -> Well, remember after a myocardial infarct,

272.586 -> you get a whole bunch of immune cells

274.826 -> that come into your heart and try to sort of tidy things up

277.554 -> after your heart attack, and when

279.075 -> you're immune cells are involved

280.689 -> with sort of tidying something up,

282.766 -> that's called an inflammatory reaction,

286.006 -> and you might start to get this inflammation

287.794 -> around the outside of your heart.

290.081 -> I'm drawing this inflammation in a pink here.

292.6 -> Pink is supposed to represent all those white blood cells

294.84 -> as part of your immune system,

296.478 -> mediating this inflammatory response here

298.997 -> on the outside of your heart.

301.087 -> Now, remember your heart sort of

302.596 -> sits inside this fibrous sack.

304.86 -> It's encased by this fibrous sort of cover

307.867 -> called your pericardium.

309.41 -> Your pericardium, peri meaning around

312.174 -> and cardium referring to your heart.

314.612 -> When you get all this inflammatory sort of stuff

317.34 -> happening on just beneath the pericardium

319.394 -> on the outside of the heart,

320.695 -> you could irritate your pericardium

322.715 -> and you could end up with a condition

324.143 -> called pericarditis.

326.686 -> Now, that's not all that tissue necrosis can do.

329.189 -> It can do some pretty nasty stuff here.

331.708 -> So, let's say that you start to get necrosis

333.856 -> of your septum here, there wall that separates

337.107 -> your left ventricle and your right ventricle.

339.533 -> Well, you could probably imagine

341.692 -> that that wouldn't be very good at all.

344.49 -> Your oxygenated blood in your left side of your heart

347.044 -> and your deoxygenated blood in your right side of your heart

350.075 -> they would mix, and you would probably end up

352.42 -> with a pretty significant hypoxemia,

355.067 -> or low oxygen level in your blood.

357.748 -> A ventricular septal defect would also cause some damage

360.651 -> to the arteries in your lungs,

363.124 -> because if you can imagine,

364.54 -> blood from this high pressure system

366.281 -> on the left side of your heart

367.907 -> would sort of cross through this defect

369.787 -> over to the right side of your heart

371.749 -> and be pushed up through to your pulmonary circulation.

375.882 -> That's not good for your pulmonary circulation.

377.914 -> It can actually cause some pretty big damage there.

381.687 -> What else will tissue necrosis do?

384.357 -> Well, what if you get that necrosis over on this side?

387.004 -> Or, really, any other muscle that forms

388.56 -> the outer wall of the heart?

391.497 -> Well, where do you think blood in the heart would go

393.378 -> if all of a sudden there was no wall anymore?

395.827 -> It would just burst out of the heart.

398.114 -> So, tissue necrosis can also cause

399.926 -> a rupture of the ventricle.

402.038 -> But remember this pericardium we talked about?

404.511 -> This really tough, fibrous sack that encases the heart?

408.203 -> The blood would then just get trapped inside the pericardium

411.744 -> and it would start to sort of build up in the pericardium

414.008 -> and track along the outer heart muscle

416.84 -> and the inside the pericardium

419.58 -> so that, obviously, would put a stress on the heart

421.669 -> and prevent it from beating as well,

423.609 -> and you'd end up with a complication

425.223 -> called cardiac tamponade.

428.45 -> Tissue necrosis is not done yet though.

431.051 -> One of the more common issues that happens

432.908 -> as a result of tissue necrosis is this here.

436.252 -> You've got these muscles in the bottoms of your ventricles

438.644 -> called your papillary muscles

441.093 -> and what your papillary muscles do

442.613 -> is they sort of hold on to the cusps of your valves,

446.77 -> the flaps of your valves, using these structures

449.626 -> called chordae tendineae.

452.145 -> They're these sort of tough, durable, string-like things.

456.278 -> So the papillary muscles and the chordae tendineae

458.507 -> work together to make sure that during a heart beat,

461.236 -> when your ventricles contract,

463.151 -> your mitral valve and your tricuspid valve

465.543 -> over on the right side, you have a set of papillary muscles

468.212 -> and chordae tendineae over there as well,

470.512 -> they make sure that the cusps of your valves

473.031 -> don't invert up into the atria,

476.107 -> and so sometimes after a heart attack,

478.046 -> one or more of these papillary muscles will become necrosed,

481.633 -> it will die off.

483.143 -> When it dies off, all of a sudden now,

484.872 -> the valve flap that it was holding on to can invert.

487.926 -> It can go up into the left atrium.

490.375 -> This means that when the ventricle contracts

492.024 -> to push blood out into the aorta, to get around the body,

495.437 -> blood can now get back up into the left atrium.

499.21 -> This is called having a leaky valve

500.94 -> or a regurgitant valve.

502.414 -> In this case, since it's the mitral valve,

504.202 -> we call this mitral regurgitation.

507.337 -> So, just before we finish up,

508.869 -> let me just draw your attention to this.

511.284 -> If your heart has decreased contractility

513.2 -> then it's going to have to work harder

514.674 -> to maintain proper profusion of your body with blood.

518.772 -> If you have a mitral regurgitation,

521.035 -> then again, your heart's going to have to work a lot harder

523.404 -> to maintain proper profusion of your body with blood.

526.84 -> If you have a ventricular septal defect, again,

529.929 -> your heart is going to have to start working a lot harder.

533.214 -> So these three conditions in particular,

535.536 -> if you develop any of these after a heart attack or not,

538.694 -> you run the risk of developing congestive heart failure,

542.513 -> which is when your heart just can't pump out enough blood

545.056 -> to meet the oxygen needs of your body.

Source: https://www.youtube.com/watch?v=m1DOnLhVuX4