If you're seeing this message, it means we're having trouble loading external resources on our website.

If you're behind a web filter, please make sure that the domains *.kastatic.org and *.kasandbox.org are unblocked.

Main content
Current time:0:00Total duration:7:31

Systolic heart failure pathophysiology

Video transcript

so a systolic heart failure your heart can't pump as hard as it used to and so it doesn't squeeze as much blood out and it doesn't meet the body's demands it's called systolic heart failure because we're talking about systole which is the phase of the cardiac cycle where the heart contracts and ejects blood to either the body of the lungs you could sort of think of it like squeezing a water bottle and squeezing the water out it's the same sort of thing except with the heart it's actually squeezing blood instead so a systolic heart failure this force of contraction of this squeezing force is a lot lower and sometimes we say that has lowered inotropy which just means the force of muscle contraction and we're just going to talk about the ventricular inotropy which is the strength of these ventricles or these bigger chambers so now think about squeezing that same bottle but just pinching it instead with two fingers you can imagine it's going to be a lot harder to squeeze the water out right well it's the same thing with weakened muscles if they're smaller and weaker it's going to be way harder to squeeze blood out and your stroke volume is going to be reduced and your body's not going to get as much blood as it used to this is all due to this weakened heart muscle well how does that muscle get weakened well it's usually caused by some kind of underlying disease that causes the death of cardiac muscle cells or cardiomyocytes I'm going to draw few these cardiomyocytes and basically they're kind of holding hands so when they contract they end up pulling on each other when they pull on each other they get a little smaller and this is what causes that squeezing motion but what if a couple of these cells died I mean obviously they're not going to pull as hard and you're not going to get as good of a squeezing motion and your hearts are going to eject as much blood as it used to so if you just look at this heart and compare it to a healthy heart you'll see that these walls are way thinner and these ventricles are way bigger these are classic signs of a heart with systolic heart failure so what are some of these underlying diseases well you've essentially got four categories and the first category is heart muscle diseases and a lot of times we're just going to call those cardiomyopathies you can essentially break that down into cardio which means heart myah which is muscle and pathy which means disease but typically with these the cause is going to be unknown but in general they tend to weaken the heart muscle and make it harder to pump blood and the second category isn't as straightforward it's it's going to be reduced blood supply but I'm not talking about the blood supply to the body I'm actually talking about to the heart itself and so coronary artery disease is a huge cause of systolic heart failure because the coronaries are what supply your heart with blood so let's get some of this stuff out of the way and move these guys over here and then I'm going to draw some vessels going to the heart muscle cells these are going to be our coronary arteries well I guess there's just one but so it's a coronary artery so usually you have blood coming down and giving oxygen to these muscle cells but with coronary artery disease you have this narrowing of the vessel because of a buildup of plaque and that buildup reduces the blood supply to the muscle cells and those cells start to die off and as we're well aware this is not a good thing because when muscle cells die off your muscle gets weaker and makes it harder to pump blood if we go one step further and that plaque builds up so much that completely obstructs or blocks that vessel then none of those cells get any oxygen at all and really they all end up dying off this is really serious because you can get whole areas of cells that die and also why heart attack is a major contributor to systolic heart failure all righty so the third class of diseases are actually valve diseases so your heart has four valves two valves that separate the upper and lower chambers and then two valves that separate the lower chambers from wherever the bloods going to either the body or the lungs so if we start with the valves that separate the two chambers we can talk about something called regurgitation and this just means that the lower chambers are letting blood go back into the upper chambers so if we just watch this heartbeat usually those felts closed when the Bloods pumped out but regurgitated means that the valves stay open just a little bit and let some of the blood go back into the upper chambers now blood is still pumped out but some is allowed to go into the upper chambers and so naturally you lose the blood that's going into the upper chambers and less Bloods pumped to the body if we think about our favorite water bottle analogy again but this time there's this like hole on the side every time you squeeze it most of the water goes out but somes going to leak out the hole and since now we're pumping less blood the heart has to work harder to maintain that same level as it had before and more work cost more oxygen but with heart failure that's the whole thing we can't supply more oxygen and more cells die off as a result and the other valve disease has to do with these other two valves it's called stenosis and that means that the blood is being pumped out through this smaller opening which makes it a lot harder to pump blood well I guess let's look at our water bottle but this time let's have our nozzle being super small just think about trying to squeeze it through that smaller nozzle it's going to be a lot harder right well turns out it's also a lot harder for your heart muscles to squeeze blood through a smaller opening and the same ways regurgitation now the heart has to work harder to maintain the same blood supply and more work equals more oxygen that can't be supplied some more cells die off all right last one this one's arrhythmias which means abnormal heart rhythm this could be a rhythm that's either too slow or maybe too fast or even uncoordinated and uncoordinated that just means that the Chamber's don't contract at the same time usually they would contract at the same time but maybe now the left ones going before the right or the right ones going before the left either way all these lead to a serious reduction in pumping efficiency which means less blood is pumped to the body and by kind of the same mechanisms as we talked about before more work means more oxygen demand and more cell death so we start to see this pattern right where each one reduces the pumping ability and this makes it a lot harder for the heart to maintain the same supply and those cells that work harder will demand more oxygen but the oxygen can't be supplied and those muscle cells die off and when they die off the heart gets weaker and your pumping ability is lowered even more so we see that pumping ability is really important and one way we can measure pumping ability is by the ejection fraction which is the percentage of blood ejected with each beat so if we look at our water bottle we can take the total volume filled and then we can also take the total volume ejected and then if we divide the volume ejected by the total volume filled and then I guess multiplied by 100 to get the percent you get your ejection fraction and usually we just talk about the ejection fraction for the left ventricle but it is possible to look at your right ventricle ejection fraction to a normal range is about 55 to 70% an abnormal range will be considered anything between 40 and 55 percent and then evidence for heart failure is anything under 40 percent