An Osmosis Video: Congestive Heart Failure (CHF) Explained

Aug 18, 2023

An Osmosis Video: Congestive Heart Failure (CHF) Explained

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Content

4.77 -> Heart failure’s used to describe a point at which the heart can’t supply enough blood

8.76 -> to meet the body’s demands.

10.83 -> This can happen in two ways, either the heart’s ventricles can’t pump blood hard enough

15.18 -> during systole, called systolic heart failure, or not enough blood fills the ventricles during

21.29 -> diastole, called diastolic heart failure.

25.36 -> In both cases, blood backs up into the lungs, causing congestion or fluid buildup, which

30.63 -> is why it’s also often known as congestive heart failure, or just CHF.

36.12 -> Congestive heart failure affects millions of people around the world and since it means

39.65 -> that the body’s needs are not being met, it can ultimately lead to death.

43.68 -> Part of the reason why so many people are affected by heart failure, is that there are

48.18 -> a wide variety of heart diseases like ischemia and valvular disease that can impair the heart’s

53.47 -> ability to pump out blood and—over time—can ultimately cause the heart to fail.

59.65 -> Alright, first up is systolic heart failure, kind of a mathematical way to think this one

65.39 -> is that the heart needs to squeeze out a certain volume of blood each minute, called cardiac

69.969 -> output, which can be rephrased as the heart rate (or the number of beats in a minute)

75.52 -> multiplied by the stroke volume (the volume of blood squeezed out with each heart beat).

81.56 -> The heart rate is pretty intuitive, but the stroke volume’s a little tricky.

85.529 -> For example, in an adult the heart might beat 70 times per minute and the the left ventricle

89.38 -> might squeeze out 70ml per beat, so 70 x 70 equals a cardiac output of 4900 ml per minute,

97.67 -> which is almost 5 liters per minute.

100.939 -> So notice that not all the blood was pumped out right?

104.21 -> And the stroke volume is a fraction of the total volume.

108.34 -> The total volume may be closer to 110 ml, and 70ml is the fraction that got ejected

114.639 -> out with each beat, the other 40ml kind of lingers in the left ventricle until the next

119.88 -> beat, right?

122.349 -> In this example, the ejection fraction would be 70ml divided by 110 ml or about 64%, a

131.239 -> normal ejection fraction is around 50-70%, between 40-50% would be borderline, and anything

138.67 -> about 40% or less would indicate systolic heart failure because the heart is only squeezing

143.72 -> out a little blood each beat.

146.5 -> So in our example, if the total volume of the left ventricle was 110 ml, but only 44

151.92 -> ml was pumped out with each beat (then you have 44 ml divided by 110 ml which is 40%),

159.73 -> and we would say that this person is in systolic heart failure.

163.64 -> Now in addition to systolic heart failure, you’ve also got diastolic heart failure,

168.4 -> which is where the heart’s squeezing hard enough but not filling quite enough.

173.14 -> In this case again the stroke volume is low, but the ejection fraction’s normal...how’s

177.79 -> that?

178.79 -> Well it’s not filling enough so there’s a low total volume, say about 69 mL, well

186.29 -> even though both are low, 44 ml divided by 69 ml is still 64%.

193.38 -> In this situation, the failure’s caused by abnormal filling of the ventricle so that

197.48 -> the chamber doesn’t get fully loaded or stretched out in the first place.

202.18 -> Another term for this is having a reduced “preload” which is the volume of blood

205.99 -> that’s in the ventricle right before the ventricular muscle contracts.

209.94 -> An important relationship between systolic and diastolic function is the Frank-Starling

214.98 -> mechanism, which basically shows that loading up the ventricle with blood during diastole

220.4 -> and stretching out the cardiac muscle makes it contract with more force, which increases

225.319 -> stroke volume during systole.

228.48 -> This is kinda like how stretching out a rubber band makes it snap back even harder, except

233.26 -> that cardiac muscle is actively contracting whereas the rubber band is passively going

237.62 -> back to its relaxed state.

240.319 -> Heart failure can affect the right ventricle, or the left ventricle, or both ventricles,

245.46 -> so someone might have, right-sided heart failure, left-sided heart failure, or both (which is

249.959 -> called biventricular heart failure), each of which can have systolic or diastolic failure.

255.09 -> Having said that, if less blood exits either ventricle it’ll affect the other since they

260.37 -> work in series, so left-sided could cause right-sided, and vice versa, so these terms

266.9 -> really refer to the primary problem affecting the heart, basically which one was first.

273.219 -> Usually left-sided heart failure is caused by systolic (or pumping) dysfunction.

278.099 -> This is typically due to some kind of damage to the myocardium—or the heart muscle—which

282.509 -> means it can’t contract as forcefully and pump blood as efficiently.

287.09 -> Ischemic heart disease caused by coronary artery atherosclerosis, or plaque buildup,

291.759 -> is the most common cause.

293.719 -> In this case, less blood and oxygen gets through the coronary artery to the heart tissue, which

298.461 -> damages the myocardium.

300.06 -> Sometimes, if the coronary’s blocked completely and the person has a heart attack, they might

305.659 -> be left with scar tissue that doesn’t contract at all, which again means the heart can’t

310.419 -> contract as forcefully.

312.99 -> Longstanding hypertension is another common cause of heart failure.

315.77 -> This is because as arterial pressure increases in the systemic circulation, it gets harder

321.08 -> for the left ventricle to pump blood out into that hypertensive systemic circulation.

326.639 -> To compensate, the left ventricle actually bulks up, and its muscles hypertrophy, or

331.499 -> grow so that the ventricle can contract with more force.

335.199 -> The increase in muscle mass also means that there is a greater demand for oxygen, and,

339.36 -> to make things even worse, the coronaries get squeezed down by the this extra muscle

343.43 -> so that even less blood’s delivered to the tissue.

346.919 -> More demand and reduced supply means that some of the ventricular muscle starts have

350.809 -> weaker contractions—leading to systolic failure.

355.68 -> Another potential cause would be dilated cardiomyopathy, where the heart chamber dilates, or grows

360.279 -> in size in an attempt to fill up the ventricle with larger and larger volumes of blood, or

365.37 -> preload, and stretch out the muscle walls and increase contraction strength, via the

370.11 -> Frank-Starling mechanism.

372.47 -> Even though this can work for a little while, over time, the muscle walls get thinner and

376.779 -> weaker, eventually leading to muscles that are so thinned out that it causes systolic

381.479 -> left-sided heart failure.

384.159 -> Ultimately the ventricle walls need to be the right size relative to the size of the

387.551 -> chamber in order for the heart to work effectively.

391.09 -> Any major deviation from that can lead to heart failure.

395.46 -> Even though systolic failure is most common in left-sided heart failure, diastolic heart

399.99 -> failure or filling dysfunction can also happen.

403.33 -> In hypertension, remember how the left ventricular hypertrophied?

407.059 -> Well that hypertrophy is concentric, which means that the new sarcomeres are generated

411.62 -> in parallel with existing ones.

414.31 -> This means that as the heart muscle wall enlarges, it crowds into the ventricular chamber space,

420.029 -> resulting in less room for blood, meaning that in addition to contributing to systolic

424.36 -> dysfunction, hypertension also can cause diastolic heart failure.

430.27 -> Concentric hypertrophy leading to diastolic failure can also be caused by aortic stenosis,

435.029 -> which is a narrowing of the aortic valve opening, as well by hypertrophic cardiomyopathy, an

440.469 -> abnormal ventricular wall thickening often from a genetic cause.

445.49 -> Restrictive cardiomyopathies are yet another cause.

448.699 -> In this case the heart muscle gets stiffer and less compliant, and therefore the left

452.71 -> ventricle can’t easily stretch out and fill with as much blood, which leads to diastolic

456.979 -> heart failure.

457.979 -> When the heart doesn’t pump out as much blood, there’s decreased blood flow to the

462.919 -> kidneys, which activates the renin-angiotensin-aldosterone system, ultimately causing fluid retention.

469.47 -> Which fills the heart a bit more during diastole and increases preload, which increases contraction

474.909 -> strength again by the Frank Starling mechanism.

478.099 -> Unfortunately, just like the other strategies, in the long term, retaining fluid so that

482.3 -> more fluid remains in the blood vessels typically leads to a large portion of it leaking into

487.09 -> the tissues and can contribute to fluid buildup in the lungs and other parts of the body,

491.659 -> which can worsen the symptoms of heart failure.

495.4 -> Aright so a major, major clinical sign of the heart not being able to pump enough blood

499.74 -> forward to the body, is that blood starts to back up into the lungs.

503.74 -> A backup of blood in the pulmonary veins and capillary beds can increase the pressure in

509.06 -> the pulmonary artery and can also result in fluid moving from the blood vessels to the

513.5 -> interstitial space causing pulmonary edema, or congestion.

518.72 -> In the alveoli of the lungs, all this extra fluid makes oxygen and carbon dioxide exchange

523.39 -> a lot harder, since a wider layer of fluid takes more time for oxygen and carbon dioxide

528.64 -> to diffuse through, and therefore patients have dyspnea—trouble breathing, as well

533.5 -> as orthopnea - which is difficulty breathing when lying down flat since that allows venous

538.31 -> blood to more easily flow back from the legs and the gut to the heart and eventually into

543.03 -> the pulmonary circulation.

545.51 -> This extra fluid in the lungs causes crackles or rales to be heard on auscultation while

549.82 -> the patient breathes.

557.95 -> If enough fluid fills some of these capillaries in the lungs, they can rupture, leaking blood

562.54 -> into the alveoli.

565.03 -> Alveolar macrophages then eat up these red blood cells, which causes them to take on

568.87 -> this brownish color from iron build-up.

571.71 -> And then they’re then called “hemosiderin-laden macrophages”, also known as “heart failure

576.5 -> cells”.

578.5 -> For left-sided heart failure, certain medications can be prescribed to help improve blood flow,

583.42 -> like ACE inhibitors which help dilate blood vessels, as well as diuretics to help reduce

588.02 -> the overall fluid buildup in the body which helps prevent hypertension from worsening

592.33 -> the heart failure.

593.33 -> Now let’s switch gears and think about right-sided heart failure, which is actually often caused

599.52 -> by left-sided heart failure.

602.05 -> K remember how fluid buildup increased pressure in the pulmonary artery?

606.63 -> Well this increased pulmonary blood pressure makes it harder for the right side to pump

610.49 -> blood into.

612.09 -> In this case the heart failure would be biventricular, since both ventricles are affected.

617.77 -> Someone can also have isolated right-sided heart failure, though, and an example of this

621.76 -> would be a left-to-right cardiac shunt.

624.63 -> In these cases, there might be a cardiac shunt like an atrial septal defect or a ventricular

628.88 -> septal defect, that allows blood to flow from the higher-pressure left side to the lower-pressure

634.05 -> right side, which increases fluid volume on the right side and can eventually lead to

638.88 -> concentric hypertrophy of the right ventricle, making it more prone to ischemia—which is

643.75 -> a systolic dysfunction, and have a smaller volume and become less compliant—which is

648.53 -> a diastolic dysfunction.

652.01 -> Another potential cause of isolated right-sided failure is chronic lung disease.

656.7 -> Lung diseases often make it harder to exchange oxygen, right?

660.26 -> Well in response to low oxygen levels, or hypoxia, the pulmonary arterioles constrict,

666.04 -> which raises the pulmonary blood pressure.

668.2 -> This, just like before, makes it harder for the right side of the heart to pump against

672.7 -> and can lead to right-sided hypertrophy and heart failure.

676.74 -> When chronic lung disease leads to right-sided hypertrophy and failure, it’s known as cor

681.2 -> pulmonale.

683.43 -> With left-sided failure, blood gets backed up into the lungs.

687.05 -> With right-sided failure, blood gets backed up to the body, and so patients have congestion

692.28 -> in the veins of the systemic circulation.

695.48 -> One common manifestation of this is jugular venous distention, where the jugular vein

700.17 -> that brings blood back to the heart takes on more blood and becomes enlarged and distended

704.41 -> in the neck.

706.19 -> Also in the body, when blood backs up to the liver and spleen, fluid can move into the

710.82 -> interstitial spaces within those organs and they can both become enlarged, called hepatosplenomegaly,

716.55 -> which can be painful, and if the liver is congested for long periods of time, patients

721.43 -> can eventually develop cirrhosis and liver failure, which would be called cardiac cirrhosis.

728.07 -> Excess interstitial fluid near the surface of the liver and spleen can also move right

732.13 -> out into the peritoneal space as well, and since that cavity can take a lot of fluid

737 -> before there is any increase in pressure, a lot of fluid can build up in the peritoneal

741.32 -> space which is called ascites.

744.01 -> Finally, fluid that backs up into the interstitial space in the soft tissues in the legs causes

749.67 -> pitting edema, where the tissue is visibly swollen and when you apply pressure to it

754.05 -> it leaves a “pit” and takes awhile to come back to its original place.

758.76 -> This generally affects the legs in most people, because gravity generally causes the majority

763.25 -> of fluid to “pool” in the dependent parts of the body, which is the legs when you’re

767.5 -> standing and the sacrum, essentially the lower back, when you’re lying down.

773.57 -> Right-sided heart failure will be treated similarly to left-sided heart failure, especially

777.31 -> because it’s often a result of left-sided heart failure.

779.89 -> Therefore, medications like ACE inhibitors and diuretics may be prescribed.

785.51 -> With heart failure, we saw that sometimes the muscle wall can stretch and thin out,

789.94 -> or sometimes it can sometimes thicken and become ischemic.

792.99 -> In either case, those heart cells get irritated, in both scenarios the cells get irritated,

795.63 -> and this can lead to heart arrhythmias.

797.04 -> With an arrhythmia, the ventricles don’t contract in sync anymore making them less

802.13 -> able to pump out blood and worsening the whole situation.

806.3 -> In some cases, patients might be treated with cardiac resynchronization therapy pacemakers,

811.67 -> which can stimulate the ventricles to contract at the same time and potentially improve the

815.57 -> blood pumped out.

817.32 -> Alternatively, for heart failure in general, some people might have ventricular assist

821.8 -> devices implanted, or VADs, which literally assist or help the heart pump blood may also

828.17 -> be implanted.

829.17 -> In end-stage situations where other forms of treatment have failed, patients might have

833.7 -> a heart transplant.

Source: https://www.youtube.com/watch?v=ypYI_lmLD7g