- [voiceover] diastolicheart failure is similar to systolic heart failure in that the heart doesn't pump enough bloodto meet the body's demands. okay, but how it is different? well, if you look at diastolic,that kind of clues us into how it's different. and if we remember thatdiastole is that phase in the cardiac cycle where the heart's just filling with blood,
so the heart's all relaxed and blood's filling into the ventricles and that's called diastole. so diastolic failure means that the heart's notfilling with enough blood. and so, if you just compare the two, if you just eyeball them, you'll notice how much less room there is with diastolic failure.
and if we bring back ourmost favorite analogy ever, the water bottles, if yousqueeze the healthy one, water ejects out, that's great. but with diastolicfailure, what if the bottle is not filled with as muchwater and you squeeze it? obviously, less water is gonna be ejected 'cause there's less inthere in the first place. it's the same thing with the heart. so, if there's less blood inthe heart in the first place,
it's gonna have a lot hardertime meeting the body's demands in ejecting as much blood. so less filled means less ejected. also, remember how a systolic failure had a lower ejection fraction which is that fraction of bloodejected with each beat. that's because there'sabout the same amount or possibly even morefilled into the ventricles with systolic failure,but there's less ejected.
so naturally, you'd havea lower ejection fraction. it makes sense. but since diastolic heart failure has both filled and ejectedlower, so both are lower, sometimes your ejectionfraction can be the same as with a healthy heart, and we would call that apreserved ejection fraction. okay, that seems alittle confusing, right? well, let's do an example andshow how that might happen.
recall that ejection fraction is equal to your volume ejected, which you can also callyour stroke volume, divided by the total blood filled which we can also callend diastolic volume because it's the volumeat the end of diastole. let's say your stroke volume is 70 ml, say your end diastolic volume is 120 ml. this would be considered "healthy";
70 divided 120 equals 58%. okay, that's within our normal range. what if stroke volume is equal to 46 mlbecause of heart failure? it's a lot lower, it's pumping less blood. but your end diastolic volumeis also lower, it's 80 ml. forty-six divided by 80 is still 58%, technically in a normal range. so clearly, the stroke volumeand the blood being pumped out
is lower, but that's kind of covered up by your end diastolicvolume being lower, too. but just because thatejection fraction's preserved, that doesn't mean we're out of the woods. it's still heart failure. but how does this diastolic heart failure get to look so much differentthan systolic failure? well, there's pretty much two ways. the first way is hypertrophywhich essentially means
like growth of muscle. when we're gonna talk about that, we mean ventricular muscle growth. when these grow, they take up more space, and since there's more spacebeing taken up the by muscles, that means there's lessspace to fill, right? secondly, is that these muscles, these growing muscles get stiffer. they don't stretch asmuch when they relax.
even though they're growing, there are these deadmuscle cells in here, too, because it's heart failureand that's a main component is death of muscles cells. so these dead muscle cellsleave this fibrotic scar tissue and this fibrotic tissue is like a bunch of connective tissue and that connective tissuehas a lot lower compliance. basically, compliance is theability for the ventricle
or for any tissue to passively stretch and expand during filling. this is super important for the heart because more stretch, more compliance means that it can fill more,it could get more blood. think of like filling a water balloon. when you put water into it, what happens? well, it gets bigger, it expands. but this is like passive,
the water is forcing it to get bigger. now think about filling upone of those glass flasks from chemistry class. i mean, i'm gonna be really extreme here just to make a point, but, what's gonna happen whenyou fill it up is just, it's not gonna get bigger,it's not gonna change shape, it's just gonna fill upall the way and then start to overflow and spill all over.
that's because it's a lot less compliant. it's probably one of theleast compliant things we can think of. it's the same with the heartwith a bunch of fibrous connective tissue. it can't relax and itcan't passively expand, and it can't fill completely. so that's what's going onwith diastolic heart failure, but how does it get like that
and how do we get theseenlarged and stiffened muscles? well, just like systolicfailure, it's a secondary disease which means that this growthand stiffening is caused by some kind of underlying diseasethat's been there before. the big one that we tendto understand the most is chronic hypertensionor high blood pressure. so when the pressure inyour blood vessels goes up, they become harder to pump against. harder to pump into.
this is kinda like blowing into a straw versus like a big tube. which one do you think it'sgonna be harder to blow air to? it's probably the smaller one, right? well, it's sort of likethat for the heart. except the heart has to pump blood through these narrowed vessels, and this is way more difficult to do. so what does your heart do?
well, it bulks up. it gains muscle and it gets bigger, so it can pump againstthese high pressures. now, both diet and diabetescan both contribute to higher blood pressure and hypertension. those are definitely big riskfactors for hypertension. and therefore, diastolic heart failure. the second underlyingdisease is aortic stenosis, and stenosis from thesystolic heart video we know
is a narrowed valve. specifically, we're gonna talkabout this valve right here, this aortic valve. then that valve goes outfrom the left ventricle and pumps into an artery called aorta. it's similar to hypertension. it's a lot harder to pump blood through this narrowedopening, as opposed to a valve that's opening all the way.
what happens? well, the heart muscle againbulks up and gains muscle so it can try to pump harderthrough this smaller valve. now, this is a littletricky though, right? because we remember that this can also lead to systolic failure. so, what gives? well, unfortunately, a lotof the mechanisms behind why in one case it might leadto this growth of muscles
like in diastolic heart failure or it might lead to thisseries weakening of the muscles like in systolic heartfailure are pretty complex and honestly, a lot ofthese mechanisms are unknown in still big areas of research. next up, we have cardiomyopathies which means heart muscles diseases and sometimes this canbe a little general, but for diastolic heartfailure in particular,
there's two that we're gonna focus on. the first one ishypertrophic cardiomyopathy which we can kinda figure out by the name. hypertrophic or hypertrophymeans muscle growth. this cardiomyopathy causes muscle growth and this is oftenwithout an obvious cause. the second is restrictive cardiomyopathy which cases stifferand more rigid muscles. this restricts theventricles from expanding.
these two cardiomyopathies kinda hit the nail in the head, right? because with diastolic heart failure, you have either stiffermuscles or enlarged muscles. finally, there are someother causes and risk factors like old age and coronaryartery disease, even, but like i said before, some of these cross path with systolic failure. again, a lot of themechanisms behind that are
largely unknown. especially as to why onemight lead to systolic failure and one might lead to diastolic failure. these are still big areas of research. with diastolic heart failure, the heart muscles either get bigger, they get stiffened or both. when this happens, less bloodfills in to the ventricles and the heart can'tpassively expand as much
and therefore, it can't relax completely. ultimately, you end up with this cycle that leads to worsening heart failure. so you start with some underlying disease like hypertension or stenosis that makes it a lot harderto pump blood to the body. to try and make iteasier, the heart muscles increase in size and theyget bigger, and then bulk up. these bigger muscles do morework, so they need more oxygen.
but with heart failure, youcan't supply more oxygen so this leads to cell death, and that cell death causesthis fibrosis and this stiffening of the heart muscle tissue. then that feeds backinto a lower blood supply making it even harder to pump blood. you could also have other diseases like hypertrophic cardiomyopathy that directly affects muscle size
or restrictive cardiomyopathy that directly affects stiffening. this cycle progresses andheart failure gets worse.
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