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Current time:0:00Total duration:9:18

Video transcript

we have our pressure volume loop and what I wanted to do is kind of explore this a little bit further and kind of a nice place to start might be with the name right pressure volume or PV loop and part of it makes perfect sense you got P there and you got V there so there's your PV and the loop 1 loop in this kind of sense is really going to represent one heartbeat right so you're going to start at one point and kind of go all the way around from systole and diastole and back and so using our PV loop the one that we kind of drew together let's actually show where systole would be so if this is kind of where we start the red represents all systole kind of going on and on and this part is really quick right just a fraction of a second point oh five seconds and then finally the aortic valve pops open and systole continues it's not like it just started there right systole starts with the initial contraction of the left ventricle continues through all of this and also on this part where the pressure is falling that's all systole in fact let me let me label that very clearly so it's clear that the red part is systole and then that leaves of course another whole half of our loop although in terms of time much more than half right because this is some of these segments take longer I'm going to do all this in blue and all this stuff in blue represents diastole kind of the other half of the heart cycle so this is when the left ventricle is now relaxing so this is systole and diastole you can see kind of next to each other on this graph so this represents one loop or one heartbeat so sometimes you hear phrases you'll hear the phrase end diastolic such-and-such ER and systolic such-and-such so what do they mean well end diastolic is literally what it sounds like it's the end of diastole kind of where I drew an arrow and what they're really talking about is a time point right so at that point in time where diastole is done you have a certain pressure or sometimes they'll talk about end diastolic volume so I'm just going right or my these two terms and a stock pressure and diastolic volume are really referring to a time point where diastole has come to an end I guess you could also say start systolic right and that's kind of the same same idea right that's where systole is also beginning where diastole is ending but you don't really hear that term you usually just hear the term end diastolic in fact I think starts start systolic is a word I might I might have just made up so let me actually just erase that but I do want to point out that the the concept would be the same right it's just a certain time point so end diastolic pressure volume is that point in time and at that point in time just remember a few things are happening right you've got for example the mitral valve just closed so I'm going to write mitral closed and if the mitral valve is closing also means the tricuspid is closing and of course I'm going to put it in parenthesis because this is the pressure-volume loop for the left ventricle so really we're not really thinking about the right ventricle but some of the events are going to be the same right so the tricuspid is going to close at this point as well and if the mitral and tricuspid are closing you know they're going to make a noise they don't close silently right and that noise we call the first heart sound or s1 and if you if you think more along the lines of what it might sound like we always kind of think of the idea of lub you know that sound of lub dub well the lub part of it comes from the closing and now you can see on this loop where that might happen now on the other side you've got kind of a similar set of stuff going on so you've got what we call end systolic right so if there's n diastolic you better believe there's going to be n systolic and this is going to be again pressure or volume so the pressure volume part gets kind of confusing but just remember what what people mean when they say end systolic all they're trying to get at is that point in time and just as before you could you could pretend to make up a term I suppose you could say well isn't that the same as start diastolic and I suppose you'd be right but because no one uses it again I'm writing it out just to kind of prove the point but I'm going to erase it so you don't get because end-systolic is kind of the the term everyone has kind of come to adopt now certain events are happening here - you've got the aortic valve closing right so this is a closing of a valve and you've also got although not here you've got the pulmonary valve closing so you could also say isn't the pulmonary valve closing and the answer is yes and these two together make a noise of course I'm going to write right here s2 and this is the dub noise when we hear lub dub now you can see where the dub part comes from it comes from that second point on our loop so we've got a couple points on a loop and these loops are used all the time in fact kind of the main reason we use these loops is because they they convey so much information very very quickly so for example let me just kind of show you why we might use these loops or how they're useful to you by showing you some of the information you can glean from them so you can actually for example take a look at these two numbers and you'll say well what is that well this is your pulse pressure now you might have heard pulse pressure before and usually usually the way we think of pulse pressure is if someone says hey your blood pressure you know reached your blood pressure is 1 I'm going to make this up 130 over 80 well I would say well my pulse pressure is just 1 or let me write that means that my pulse pressure pulse pressure is just the two numbers subtracted by each other right so it would be pulse pressure would be 130 minus 80 or 50 right so this is just kind of an example right so this would be pulse pressure kind of the way we usually think of pulse pressure just your systolic pressure minus your diastolic pressure but look in your PV loop remember this is not your aortic pressure which is what we measure usually in your arm this is actually your left ventricular pressure right so left ventricular pressure is going to be very very similar you've got kind of the low end right here and you've got the high end and the low end is really the lowest that the blood pressure in the aorta is going to be and the high end is the highest that the aortic pressure is going to be so your pulse pressure you can kind of figure out using this loop I would say well on this loop the pulse pressure equals 120 because that's the high end right there minus 80 and so I would say my pulse pressure equals 40 millimeters of mercury that would be my my answer if someone asked me what is the pulse pressure on this PV loop so the cool thing is that you can actually use these PV loops to calculate things like pulse pressure now another interesting thing you can quickly calculate is this I'm going to just kind of draw with green a different color and this is my stroke volume stroke volume all that means is the volume of blood that leaves my heart with every stroke right so you've got at the one end when my left ventricle is really full you've got 125 and then when it finally kind of squeezes as much as it's going to you end up with 50 so my stroke volume is literally just 125 minus 50 and that ends up being 75 so if someone said hey what's your stroke volume here I would say well it's 75 milliliters so one final thing that I don't want to kind of over volume well Mew but I want to really point out all the kind of interesting things you can learn from this PV loop is what we call the ejection fraction now this is just the stroke volume which we just calculated to be 75 right divided by the what they call peak volume or total volume in the left ventricle when it's full I'm going to call it peak volume so in this case what is the peak volume what it's 125 right that was the highest amount of blood that we got into this left ventricle so the ejection fraction would be 75 divided by 125 and notice that the volumes cancel right so you all you're left with is just two numbers over each other and in this case you get 60% I'm writing it as a percent you could also say it's 0.6 or 0.6 but usually we talk about it in percentages so I would say the ejection fraction using this PV loop is 60% so you can you can look at these PV loops and you can learn certain words like ends diastolic and systolic you can calculate things like your pulse pressure your stroke volume or ejection fraction so they basically give you a ton of information and that's why we always use them