Transcript for:
Basics of EKGs

what's up ninja nerds in this video today we're going to be talking about the basics of ekgs let's go ahead and get started all right ninja nerds so when we talk about ekgs we obviously have to start with the basics understanding the physics understanding the physiology before we actually start going through and reading 12 lead ekg cases and determining what's going on so what i want to do is i want us to take us a stroll really quick through some basic physics and physiology which will really prepare us when we start going through a systematic approach of ekgs in order for us to under to understand that and to start this process what i want us to do is i want you to imagine imagine i have this ventricular myocardium here and i'm just going to take and cut like a chunk of tissue out and place those chunks of tissue here in this box layer okay then what i'm going to do is i'm going to get a little evil and i'm going to put some electrodes on each end of this tissue right i'm going to put a positive electrode on that side of negative electrode on that side then what i'm going to do is i'm going to stimulate i'm going to come at this end of this tissue and i'm going to stimulate i'm going to provide some electrical stimulus when this tissue becomes stimulated it actually you know cells they undergo depolarization right positive ions like calcium and sodium ions will flood into these cells cause them to flip become positive depolarize them right and you know there's little junctions right if i had like a little hole between this cell and this cell there's little gap junctions and so those sodium ions and calcium ions can move through those gap junctions from cell to cell to cell to cell creating kind of this electrical signal that's being propagated from this end of the tissue to this end of the tissue and what kind of charge is being propagated well remember this cell is resting so originally it's kind of slightly negative right then it becomes positive positive positive positive so there's a flow of positive charges moving in which direction if i go ahead and apply a stimulus at this end there's going to be a flow of positive charge moving towards this positive electrode now why is that important if i take the positive electrode and i hook it up to an ekg machine it should cause a particular type of deflection right when you look at ekgs all they look like is you see upward deflections downward deflections you see flat lines what does that mean i'll tell you what it means if a particular tissue is generating action potentials depolarizing waves that are moving towards a positive electrode it'll get red from that electrode send it to the ekg machine and produce a positive deflection that shows up on the ekg so i want you to remember that a flow of positive charges moving towards the positive electrode of any kind of lead of the 12 lead system should produce a upward deflection okay let's take the opposite scenario let's say i take and i put a negative electrode here on that same side a positive electrode on this side but now what i want to do is i want to stimulate this end of the tissue okay so i'm going to go ahead and stimulate this into the tissue stimulate it it'll depolarize positive charges will then flow from this cell to this cell to this cell to this cell via the gap junctions right and it'll move in which direction towards the negative electrode or what we like to say is away from the positive electrode right and again what kind of charges is flowing here positive charges whenever this flow of positive charges is moving away very very important away from the positive electrode it'll then get picked up by the electrode send it to the ekg machine and produce a downward deflection so again downward deflection alright so to quickly recap positive charges are flow electrical activity moving towards positive electrode upward defection if there's a positive charge moving away from the positive electrode downward deflection okay let's let's switch it up a little bit so we'll change it up a little bit because this is going to become very important when we go through this entire ekg waveform and explaining what all these deflections are indicating what if i do one more thing i put a negative electrode here on one side of the tissue i put a positive electrode here on this side of the tissue right and now what i'm going to do is i'm going to actually have these cells you know whenever cells depolarize right for example let's say that we took this one it depolarized after it depolarizes it then has to start to repolarize so let's pretend for a second that these cells will repolarize right and let's say that they're repolarizing just for the sake of this argument here let's say that they're repolarizing going in this direction right so for example this cell will become negative this cell will become negatively charged negatively charged negatively charged so it's going to be moving in this direction just as an example right so i have a flow of negative charges that is moving from the positive electrode towards the negative electrode right when negative charges are flowing towards the negative electrode guess what it does the same thing that would happen if positive charges are moving towards the positive electrode produces an upward deflection so in this case negative charges to negative electrode will produce a upward deflection so very important you'll see why whenever we start going through this the last thing i want you to remember is that there's parts where there is no deflection via upward or downward sometimes it's just flat all right an isoelectric line what could that be indicative of let's say here i take this tissue negative electrode on this side positive electrode on this side but now the tissue is oriented to kind of in a different direction you know this is an axis right if you kind of imagined an imaginary line going from this electrode to this electrode there's an axis of that lead okay if i were to stimulate this into the tissue which way is it going to go upwards right so if i stimulate this into the tissue and i cause this to depolarize this to depolarize this to be polarized and so on and so forth what is the direction of positive charge is going to look like it's going to start moving towards the axis of this lead and then after it passes through the axis it'll move away from the axis of that lead you know what actually happens but your ekg is so smart your ekg machines are so smart generally whenever this kind of charge this positive charge that we have flowing here down this tissue perpendicular to the axis of the lead originally as it's going towards the axis it actually produces a positive deflection and then it moves away from the axis of that lead but since it's the same amplitude on both sides of the axis of that lead the deflections will be equal to one another equipasic and then guess what happens the ekg machine actually will cancel them out and make a kind of an isoelectric line so you can remember two things whenever there's like no net movement of electrical activity there'll be kind of a flat line or whenever the electrical activity of the heart is moving perpendicular to the axis of whatever lead we may be looking at okay i think we have a pretty strong idea now about what causes a positive negative deflection or a straight line now what i want us to do is let's take one lead that's the most commonly used lead in the rhythm strips of 12 lead ekgs lead 2 and map out the entire ekg waveform all right engineers so now let's go ahead and take and i want you to trust me for right now we'll go through all the 12 different leads and understand them a little bit more but for right now just trust me that the lead that we are looking at in this kind of example that we're going to follow throughout the entire ekg cycle is lead two lead two usually the negative electrode is kind of on the right arm or right side and then the positive electrode will be on the left leg okay and so it creates this axis if you imagine an imaginary dotted line the axis is going in this direction from negative to positive okay so remember for the most part where is the flow of positive charges going with respect to the positive electrode think about the positive electrode as an i looking towards the negative electrode it's looking for those positive charges if it's coming to it it's going to be a positive if it's going away from it it's going to be a negative okay so let's start off let's start off with the first part of the ekg whenever a the the atrial cells you know all this entire ekg activity starts within the atria the atria they have this structure called the sa node you know the sa node it's located within the upper kind of top right portion of the atria near the entry of the superior vena cava so that'll be our sa node correct that tissue has special types of pacemaker cells that have the ability to generate action potentials and spread those action potentials throughout the atria going towards a particular direction and the ultimate direction that these electrical potentials want to go towards is this big fat structure here sitting at the top of the interventricular septum and that is called our av node okay so let's say here that we have our sa node it decides hey baby i'm going fire i'm gonna send some action potentials so it starts sending action potentials originating in the right atrium okay so it'll send action potentials kind of all throughout this direction right kind of spreading from the right atrium all the way towards the left atrium here's what's interesting though if you were to take the mean of all or the average of all of these vectors that are spread throughout the atria the mean vector that is generated by the depolarization of the atria from the sa node to the av node one big vector would really kind of look like it's going straight to the av node so really if i took the mean of all of these little vectors that was generated by the sa node spreading out to the atria the mean vector that's generated from the sa node to depolarize the atria is going downward and leftward towards the av node now that's the positive voltage right there right so here let's get rid of all these like little guys so that we can completely understand here that this right here just this arrow here this is a flow of positive charge moving from the sa node to the av node but remember it's the main vector of all atrial depolarization which direction is that positive charge flowing with respect to the positive electrode of lead two it's moving in the direction of the positive electrical e2 what does that mean positive charges flowing towards the positive electrode upward deflection boom we got ourselves a p wave baby so there is our p wave so we have our p wave and what does that indicate this indicates atrial depolarization now more particularly if we really really want to be particular though that p wave if it looks just the way it's supposed to which i know it may sound a little odd what else could it look like it can look very different sometimes and we'll explain that throughout later videos but if the p wave looks the way it's supposed to in other words it's a sinus p wave that means that that p wave was generated by the sa node so if you have an upright p wave looking like the same morphology throughout that atrial depolarization it actually occurred because the sa node was the one that generated the electrical activity to depolarize the entire atria very very important okay so we already started with the first part of our ekg let's move on to the next part if you look here we have our p wave right so this is our p wave but then we have this portion of the ekg where there's this flat line okay well i want you guys to remember what does the flat line indicate the flat line indicates that there's either no net movement of electrical activity or that the electrical activity is being directed perpendicular to the axis of that lead that's what it means right so let's understand why there is this flat isoelectric line here let's go back to where we were before here we have our sa node at the top of the atria it generated a bunch of depolarization vectors and where was that directed toward do you remember the end point that we want all of this electronegativity to kind of come to we wanted to go to the av node at the top of the interventricular septum we said that there's a bunch of different depolarization vectors but the primary main depolarization the mean vector from all of those is directed downward and leftwards towards the av node so that's our atrial depolarization vector we said that gave us a positive type of deflection right the p wave now let's say that the electronegativity finally gets to the av node the av node becomes depolarized so it's starting to become positive positive positive but guess what the av node is a very nice little wader it takes its time with the electrical activity it slows down the conduction a little bit sometimes like about a point one second delay that the av node just hogs all the electrical activity and says hey stay here with me baby and then i'll send you down to the ventricles so what happens is the electrical activity hits the av node the av node starts kind of taking all this electrical activity it becomes depolarized but it holds that electrical activity within it before it decides to send the action potentials down to the ventricles so it is positive charge but that positive flow of charge is not actually moving in a particular direction to produce any upward or downward deflection so that's how we had this isoelectric line now very important to understand here that if we take from here that point of where the p wave ends unto where this line kind of ends because there's going to be another little jaggedy point that we'll talk about here with the ekg this right here is a very specific type of name here this is called our p r segment okay that's the pr segment the next part that we really need to differentiate here if i were to draw like another let's say i drew another one here's my p wave my pr segment there if i drew the distance from the beginning of the p wave all the way until that pr segment ends that is referred to as the pr interval so make sure you understand that okay so it's very important to remember the difference between these two but what do we know we know why we have this isoelectric line it's because the depolarization that moved from the sa node got to the av node av node is a very slow conductor holds the electrical charges for a certain amount of time about a 0.1 second delay then it says okay i'll send the electrical activity down to the ventricles now we understand the p wave in the pr segment now the next thing that we're going to do is move on to the next part all right so now we understand the p wave of the pr segment and we kind of formed at this point our pr interval now we start going to this next part of the ekg do you guys remember what that part is so if you guys remember we have our p wave we already understand what that is indicating then we have our pr segment to gather the p wave and the pr segment make our pr interval then we go into this next part which is kind of a downward deflection let's kind of quickly very very quickly recap p wave is what again sa node firing generating a mean vector towards what structure the av node right av node holds on to that electrical activity because it's kind of a slow conductor has and receives all that positive charge but does not conduct it down the bundle bundle of hiss and bundle branch system yet so that causes that pr segment now here's where it gets cool we have from the av node the bundle of hiss right or the av bundle which then splits into what's called the right bundle branch and then through your left bundle branch now your left bundle branch actually has two other small branches left anterior and left posterior fasciculars but we're not going to we'll talk about a little bit later okay when it comes to axis and deviation but for right now i want you to remember simply there's a right bundle branch and a left bundle branch okay here's what's really really interesting whenever that depolarization finally moves from the av node down to the bundle of his and then through your bundle branches do you know what's really interesting your left bundle this is the left bundle branch it is actually responsible for depolarizing the interventricular septum not really the right bundle branch it's primarily the left bundle branch that depolarizes your interventricular septum so if you think about that if it's causing these small little depolarization vectors that are moving towards the right and maybe even a little bit kind of upward superiorly then what would the mean vector of all of those little guys look like on this diagram it would look like this right so like i said you should have all of these vectors that are pointing towards the right because it's going to be the left bundle branch depolarizing the interventricular septum from the left towards the right and it even is oriented a little bit upwards because of the shift of the heart two-thirds of the left of the midsternal line so this should be the net depolarization vector of the interventricular septum or septal depolarization okay if that's the case then what direction is that flow of positive charge moving with respect to the positive electrode of lead two it's moving in the opposite direction so if it's moving in the opposite direction or away from the positive electrode lead to what does that do causes a negative deflection so that's where we get our negative deflection that negative deflection has a very specific type of name so we know we have p wave right that's our p wave then here what do we have we have our q wave that's our q wave and what does the q wave indicate that's very very important it is indicative of septal depolarization so what is the q wave indicative of it's best represented in this diagram but the q wave is indicative of septal depolarization okay one more thing that i really want to kind of get across here because sometimes when we go further throughout these ekg lectures you guys will see that there's something called pathological q waves q waves are are normal they're a physiological part of our ekgs okay whenever they become larger so in other words they become very wide and we'll talk about what that what that actual distance is or whenever they become very deep they go have a very long kind of depth that they really have a negative downward deflection and a couple other things and particularly like what kinds of locations you really don't want to see them in then they can be called pathological q waves so again remember q waves are a normal physiological part of the ekg it's just the size of it really determines whether it is physiological or pathological and sometimes what's very interesting is you may not even see the q waves within a 12 lead ekg all right so we have the basic understanding here we know that the p wave is indicative of atrial depolarization vector pointing down to the left pr segment indicative of atrial depolarization but no net movement q wave indicative of septal depolarization moving upward and to the right away from the positive electrode let's go to the next part of the ekg all right ninja so now let's go into the next part here so we have our p wave right we know what that indicates we have our pr segment we know what that indicates right so here we'll put down here p r segment we have our q wave we know what that now indicates but now we go from this negative deflection into an upward deflection what the heck does that indicate don't worry guys i got you so again sa node this is going to build like just buried into your brains you guys will never forget this now the sa node sends an atrial kind of depolarization vector that's directed downward in what direction towards kind of the left okay let me just draw your bundle branch system here so again which direction would that be moving it'll be moving atrial depolarization downward and to the left as you're going towards the av node so that's going to produce that positive deflection atria stay depolarized don't have any net movement because they're slow conductors pr segment goes down through the bundle branch system but remember that the left bundle branch is what really depolarizes the septum and that creates this net vector that moves in which direction moves to the right and then upward which creates again that negative deflection all right now let's go to the next part here the electrical activity will then continue to move down the bundle branches so it'll eventually go you know from here down the left bundle branch it'll start to spread outwards like this from the bundle branches through the purkinje system you kind of get this kind of direction here so then we'll go through the right bundle branch and then through the right brick energy system and you guys get the point we're generating these vectors as we're going down through the interventricular septum towards the apex and then up towards kind of the bases here's what i want you guys to think they're like holy crap there's so many arrows where the heck is the net vector all right remember which ventricle is supposed to be thicker it has more myocardium meaning that it's going to conduct more action potentials meaning that it'll generate higher voltages meaning it'll generate a larger positive deflection which side the left ventricle that left ventricle be thick right so the left ventricle is going to generate more uh intense of a net vector right so if we were to kind of say let's see imaginary line here cut in half right ventricle on this side left ventricle on this side all of these net vectors here will create i mean all of these little vectors here will create one net vector all right from here to here what what will that look like it'll be pointing like this okay so that's going to be the vector from the left ventricle so this is again a flow positive charge then let's say over here you have the right ventricle the right ventricle is generating all these electrical activity that's moving in this direction right so it's going to have a smaller okay it's not as thick so its electrical vector may be a little bit tinier okay and it may kind of look like this because again the left ventricle is way thicker than the right ventricle and again this is going to be a flow of positive charge so here's what our different vectors would look like if we only imagined it generating the left ventricle or the right ventricle but we want the mean qrs vector in other words we want the equivalent of what the vectors would be additive of the left ventricular vector and the right ventricular vector so it should be if i take this one and this one which one's bigger you usually want to kind of go in the middle if they're equal but they're not equal right that left side is way bigger so because of that it's going to start the mean of these two will lean a little bit more towards the left so your net vector here between these two is going to look like this so this is our net qrs vector and again it's a flow of positive charge and i erased it before but let's say here's our positive electrode of lead 2. if this is our mean qrs vector which is the net sum of the left ventricular vector and the right ventricular vector which direction is that flow of positive charge moving towards with respect to the positive electron it's moving towards it right if it's moving towards the positive electrode what does that cause a nice positive deflection what do we get a positive deflection what does this mean vector indicate well we know it's going to cause a positive deflection why because there's a flow of positive charges from this mean vector moving towards the positive electrode of lead two and we know that based upon our discussion that causes a positive deflection what is that positive deflection here called that is called our r wave okay so that's your r wave so if you want to think about it this would be the r wave this would be the vector particularly for the r wave in the left ventricle and this would be the vector for the r wave and the right ventricle so this is the mean of them so we could kind of say if we want to this is the mean r wave vector okay all right so that discusses that part of the ekg now let's move on to the next part so we have our p wave that we generated which was again what that was when the sa node was firing generating a atrial depolarization vector aimed towards what structure the av node right and the av node once it's actually depolarized it holds on to that electrical activity for a bit it doesn't let it move down through the ventricular bundle system and that is going to be the pr segment right collectively the p wave and the pr segment is called what that is called your pr interval then what happens is these av bundle will then finally say okay time to send this stuff down to the bundle system so send it through the av bundle the right bundle branch and the left bundle branch if you guys remember the left bundle branch will generate depolarization vectors that are aimed towards the the right and upwards moving away from the positive electrode and that causes this downward deflection here called the q wave so now we have our q wave then what happens is the depolarization vectors will then move down into the left and down and to the right they'll create a vector moving towards the right a vector moving towards the left we want the mean of those two but because the left ventricle is thicker it's going to cause the mean r wave vector to be pointed downwards and to the left more so you should get a downward vector like this and that's what caused our r wave well now we go to the next part the next part here is we had the depolarization spreading from the inner part of the myocardium all the way to the outer part of the myocardium after it depolarizes the inner to outer part of the myocardium it's not only going down in this way so it goes down and it goes from inwards to outwards but it also moves superiorly towards the base of the heart as it does that look at the direction here let's use our purple marker here this kind of depolarization as we're saying here it moves down like this it also moves like this and it starts moving towards the actual base of the heart and the same thing for this side it moves downwards like this but it also move upwards like this as it does that there's going to be this kind of like basal ventricular kind of depolarization and if you look at it which direction is it actually kind of pointing it's pointing upwards and then towards the left for both of them so if i were to draw kind of a little depolarization vector on this side it should go this way and a little depolarization vector on this side should go this way okay so these are going to be the depolarization of the ventricles towards the bases and again it's because they're moving down and upwards so if it's moving upwards and generally towards the left and it's a flow of positive charge what direction is that moving with respect to the positive electrode of lead 2 it's moving away from it what does that cause a downward deflection what do we get a downward deflection what in the world is that downward deflection called this is called the s wave we'll actually put that in here s wave for this part okay so what is the s wave indicating it is still ventricular depolarization but at this point it's more towards the base part of the ventricles rather than the entire kind of like thickness of the ventricular myocardium right and left ventricle thickness part from inner to outer that was more the r wave okay and then the q wave is more septal depolarization all right we've covered that let's pop right over into the next part here all right quick recap we're not going to go through all of this intensely again we're not going to draw the vectors i think by now you guys should know it all but we'll draw here our kind of our bundle system here to just be consistent okay here's our right bundle branch here's our left bummer branch okay so we know now we definitely we're professionals i think right ninja nerds at this point we know the p wave we know what it means we know the pr segment we know what that means we know the q wave we know what that means we know the r wave we know what that means and we know the s wave and we know what that means okay here we go you get to this next part which is very interesting which is going to be kind of like this flat segment here kind of there's kind of a little up stroke here but really it's this isoelectric line that we really need to focus on this isoelectric point here where it's staying kind of in a flat line just like the pr segment was this is called the st segment st segment is basically when the entire ventricular myocardium is completely depolarized remember how in the av node the av node was depolarized and it stayed depolarized but it didn't actually kind of like cause a movement of charge down into the av bundle it kind of just stayed in that av node in the same way the entire ventricular myocardium has already been completely depolarized it's super positive it hasn't begun to repolarize yet and there's no more movement of any kind of charge it's just been depolarized and it's just about getting ready to repolarize but it's stuck in this depolarization state but there is no net movement of any of that electrical charge if there's no net movement of electrical charge what will that do to the ekg is there a positive is it negative it's an isoelectric line so that's where we get this part here which is called our st segment and this is a very very important segment when it comes to pathology so we'll talk about this in future videos okay all right so we understand that let's go into the last part of the ekg analysis here all right so the last part of the ekg okay so we we know this by now ninja nerds we should be professionals at this whole waveform stuff we know the p wave okay we know our pr segment we know what all of this stuff indicates by now we know our q wave we know our r wave we know our s wave let's lengthen this st segment here a little bit more though so we can make sure it's a super profound st segment there and then we have one more wave that we have to talk about here and again what is this port here that we just finished discussing this is our s t segment okay all right here we go so the first thing that we need to do is understand how the heck we get this upward deflection which is the t wave okay let's make sense of everything that we've done so far so far without going through all of those vectors here's our av node we'll just draw an sa node here sa node av node we got our bundle of hiss we got our right bundle branch we got our left bundle branch right what did we leave off with at the last point here this entire ventricular myocardium the entire thickness of the ventricular myocardium was depolarized now here's where it gets good baby whenever a tissue depolarizes in order for it to relax in order for it to be stimulated again it has to repolarize in other words has to go back to its resting membrane potential which is what kind of voltage inside of the cell negative voltage so at one point it was all positive charge throughout this entire ventricular myocardium but what happens is imagine the charges flipping from the outside of the myocardium to the inside of the myocardium so it's positive here then it goes negative and then it was positive here negative so imagine like this let's say that we kind of use it as an example here positive positive positive positive that entire ventricular myocardium was positive right and during the st segment i'm going to flip each one but i'm going to move in this direction i'm going to repolarize that one repolarize that part of the myocardium repolarize that one and repolarize that one the negative charge is flipping in which direction it's going backwards in the direction that the mean r wave vector was right because if you think about it it's going to be the same thing it's going to be negative charge flowing this way from the right ventricles negative charge flowing this way from the left ventricles so this is going to create a nice vector thick vector right that would be pointing upwards and towards the right and this would be kind of creating like a little baby negative charge vector that's going to be pointing upwards and towards the left but again we want kind of the net vector between those two so what's the net vector well again this one's the bigger net value this one has the bigger vector the bigger amplitude so we want between we want in the middle we want the net of those two but it's going to be leaning more towards this side so what happens is in this case this vector will kind of look like this this is going to be the net vector between these two and what kind of charge does it actually have what what flow of charge is moving in this direction from the outer part of the myocardium to the inner part of the myocardium negative charge now here's where we got to go back to remember what we talked about if positive floats towards positive it's an upward deflection if positive moves away from positive it's a downward deflection what do we say happens when negative charge moves towards negative charge or negative electrode it's going to produce an upward deflection negative charge oriented upwards towards that negative electrode that is where we get our upward deflection and that upward deflection is indicative of this is our t wave and what does the t wave indicate it indicates the ventricles are repolarizing so what does it indicate it is indicative of ventricular repolarization beautiful so at the end of this to really quickly recap this what does the p wave indicate atrial depolarization what does the qrs indicate ventricular depolarization what does the p wave indicate ventricular repolarization now that we've understood where these waveforms come how they're actually why it's up why it's down why it's isoelectric let's do the same thing with all the other 12 leads that are a part of our ekg all right engineer so at this point in time we've covered what the ekg kind of waves and segments and all the different components of that should look like in one lead right lead to i told you usually lead 2 is the common most common lead used in a rhythm strip of the 12 lead ekg but we only looked at one out of a total of 12 total leads that you can have in an ekg and so that's important to remember that what are these different 12 leads we'll talk about them individually but there's what's called three limb leads lead one two three not too bad then there's three augmented unipolar limb leads and that's avr avl and avf and then there's six precordial or chest leads v1 to v6 so if you add all of that up that's three plus three six six plus six 12 12 total leads so we should we don't have to but we should see what all of these waves would look like if we utilize the vector format that we talked about above and each of those 12 leads now these are tiny little arrows and there's a lot of them so it's going to be kind of like confusing so we're going to go through it each one by one but we're going to kind of i'll use my hands to kind of gesture in what direction it's moving when as well before we start going through this you should know what the heck lead am i looking at where the negative electrode is on this side the positive electrode is here same thing with these so let's quickly take there was this guy who made up this lead system eintoven he came up with what's called eindhoven's triangle right so in tovan's triangle is this simple kind of method where the heart is kind of situated here in the center and we create these axis of particular leads with lead one two and three so what happens is we take an electrode and we put that on the right arm we put one on the left arm we put one on the left leg and then we put a neutral one usually on the right so let's say here i recommend this as right arm left arm left leg there's three total leads this is going to be lead one this is going to be lead two and this is going to be lead three and you can kind of already see that if i were to take kind of a look with the respect to the heart this one's kind of going horizontal here that's going to be lead one this one's kind of going diagonal in this way that's lead two and this one's kind of going diagonal and this way that's lead three but let's say it makes sense of where the negative and the positive is for the axis of lead 1 there's a negative electrode that's placed on the right arm and a positive electrode that we have on the left arm then that creates an axis and that's that axis that we see right here okay that's the axis of lead one that we kind of situated on the heart there lead to the axis of lead 2 you have a negative electrode on the right arm and a positive electrode on the left leg and that creates this axis that's coming down diagonally and again if you imagine i took this kind of a dotted line and put it over the heart you can see their negative electrode here at the top positive electrode here at the bottom towards the left same thing lead 3 put the negative electrode here on the left arm positive electrode here on the left leg what does that create it kind of creates this axis here that's going down this way if i were to take this put that over the heart negative electrode should be over here positive electrode should be down here so that's where i'm getting all of these electrodes i don't want you to think i just made them up and put them there willy-nilly right so this is lead one this is lead two this is lead three the beauty of all of this is that we already know what lead two should look like right we should already know so if i were to draw out that utilizing all those vectors that we talked about we should already know that there should be an upward up right p wave a pr segment q r s st segment and then our t wave right here for right now i want you to trust me but guess what leave one lead two lead three all of them are pointing in the same direction so for right now i want you to trust me but we'll go through it there may be slight variations because of the axis of those leads with the respect to the vectors but for the most part you're gonna get the same kind of waveform here that you would get in lead two that you would get in lead one in lead three so let's go ahead and look at this all right here's my positive electrode let's start with the p wave which way is it going i have this arrow up here but which way is it going downwards and to the left is it going towards the positive electrode yeah upward deflection then i go septal depolarization right that's my q wave it's going upwards and kind of towards the right is it which way is it going with respect to the positive electrode it's going away from it so that's going to be a downward deflection then i go to my sep to my actual entire kind of like mean r wave vector it's going down and to the left it might not look like it's going straight towards the positive electrode but in general the direction of where it's going is moving towards the positive electrode so that's going to produce a positive deflection then you have the depolarization at the bases of the ventricles that's moving upwards and towards the right that's moving away from the positive electrode that's going to be the s wave and then again your t wave is this negative depolarization that's moving in which direction it's going this way what is it moving towards the negative electrode so it should be a positive deflection the same exact thing happens with lead three so if you look at it the positive charge is down there so if you were to do this we don't have to do this because it's going to make the exact same sense if you were to follow all of these vectors you would get the same kind of situation there for lead three okay so what i want you to remember is lead one two and three their waveforms should be pretty much the same on a 12 lead here's the next thing i really really need you guys to know imagine the positive charge as an eyeball okay imagine it as an eye and you are looking at the heart from that view wherever that positive charge imagine that is where you're looking at the heart if that's the case then lead one is looking at what part of the heart directly what's the first thing that that eyeball sees this portion here it sees that left ventricle but particularly like the lateral wall more towards the top so we call that a high lateral wall of the left ventricle so if i were to highlight over here let's highlight it in a very nice color here let's use this beautiful like turquoise color here this portion right here would be what one lead one sees so lead one would give us an idea of what kind of electrical activity is taking place in which part of the heart the high lateral wall of the left ventricle okay that's very very important especially when we get to stemis okay the next one only two and lead three you know what we're so lucky because if you look here lead two and lead three are both looking at the heart from the bottom so the first part that they see is this part here and this part there that's the inferior portion of the actual what that's the inferior portion of the ventricles so it looks at the inferior portion of the heart so this would be what portion would be looking at this this would be leads two and lead three would be looking at the inferior wall of the heart okay and that includes the right ventricle and even a little bit of the left ventricle all right so that's important to remember that so now we have a pretty good idea of what lead 1 lead 2 lead 3 ekg waveform should look like and what part of the heart they tell us where the electrical activity is kind of altered in some way all right now let's talk about the augmented unipolar limb leads do the same kind of thing with these vectors and then talk about what views or what portions of the heart they tell us about all right so we finished our limb leads now let's talk about the augmented unipolar limb leads now the thing is is that these can be kind of annoying and complicated if you really get into the physics of them we're not going to do that we don't need to it's not necessary because you know what your ekg machines are so smart that they have the ability to kind of switch the electrodes kind of simultaneously and so it's really kind of cool what they can do we'll go into a brief discussion of what i'm talking about so remember i told you that there's three types of augmented unipolar limb leads so what are those the first one that we'll talk about is avr so this is going to be a v r augmented unipolar limb leads that's going to be for the right side and avl and avf okay so what happens is you're still kind of using that same lead system the same triangle there was another guy named wilson who came up with this idea but it's the same kind of concept from the limb leads okay the only thing that's different is is that what happens is that the ekg machine will switch the negative electrodes on two corners like on the like for in this case there'll be a negative electrode on that left arm and a negative electrode on the left leg and it'll put a positive electric electrode on that right arm and what happens is that means that if you were to kind of again follow the axis where does that mean the axis of avr is whenever you have two negative charges the actual kind of mean point is actually situated here in the center so actually when you look at this the vector is actually going to be kind of pointing this way towards that right side so that's where that kind of avr comes from so if you were to imagine here for a second imagine that's where that vector starts this is where i would imagine i had this negative electrode situated this is the axis of that avr okay so i want you to again imagine here this is the eyeball you're looking at the heart from this direction let's follow all the wave forms p wave where is it going i know it's right there but there's a lot of these waves very close but again this top one right there that's your p wave it's going downwards and to the left with respect to the positive electrode of avr where is it moving away from the positive electrode oh what does that mean that is a downward deflection so that means you're gonna get something like this oh shoot then we go here we got this next part what is this that septal depolarization that moves towards the right and upwards that means it's going to the positive charge that's going to be a upward deflection maybe a little guy like that then the ventricles right you have your mean r wave vector that's pointing downwards to the left that's moving away from the positive electrode that's a downward deflection and then you have this depolarization that's occurring at the bases of the ventricles that's moving towards the positive electrode that's a upward deflection okay and then from there you go into your st segment right which is where the entire ventricles are depolarized they aren't having a net movement and then what happens ventricular repolarization i know you can't really see it but this was the positive charge that was for the r wave what do you think that negative charge is that's for the t wave right so then after the ventricles depolarized what happened you guys remember what happened from above then what happens is you start to have this ventricular repolarization which is a negative charge a negative charge moving towards the positive electrode okay in other words if you were to imagine remember we imagine that this is our neg our imaginary negative electrode between these two points here this is moving in which direction with respect to that negative electrode away from it and so because it's moving away from it that is going to produce a negative deflection and this is what you would get here for your actual ekg waveform with respect to this uh avr all right so now if you think about this we now kind of see what our waveform would look like our ekg and avr do you know what's really interesting about this it's literally the exact opposite of lead two and technically lead one and lead three but lead two is kind of like our poster child of what the ekg would really look like so if you imagine remember what lead two did had an upward p wave remember what the uh the q wave was it was a downward deflection remember what the r wave was upward deflection remember what the s wave was a downward deflection do you remember what the t wave was and upward deflection this is the exact opposite that is going to become so so important later when we start talking about how to determine rate and rhythm if something is in sinus rhythm or not if there's ectopic foci that are developed we'll go into all of that later so it's very important out of all of this stuff that we're just talking about leads remember that avr and lead 2 should be opposite of one another and therefore their waveforms now we can go through this all again i think it's going to be kind of repetitive but if you follow the same thing avl again the ekg machine is smart creates negative electrodes on the right arm and left leg and then what happens is the imaginary negative charge then would form between those two going towards the positive electrode that way so you have an axis like this right so that means that the avl the i that positive charge will be looking at the heart like this okay and if you followed every single waveform from that point on utilizing everything we talked about guess what it's the exact same as lead one lead two lead three hey let's take another step guess what the next one below this is the exact same the only one that really should be opposite is avr every single other one of them lead 1 2 3 avl avf should all pretty much look the exact same the only one that should really look different is avr there may be variations from ekg to ekg but for the most part in a perfect world lead one two three avl avf should look the same okay so we should have an upright p wave qrs t upright p wave qrs t if you wanted to go through these definitely stop the video and follow each of these depolarization vectors and try to map all of them out and again you'll get pretty much this again there may be a small variance from either one from all of these but for the most part same for avl avf as one two and three avr should be the one that's completely different all right we now understand that before we go into the heart showing the portions of the heart we should actually finish explaining this avf though so again same thing as we talked about before with avr and avl the machine's very smart right so what it does is it turns a negative electrode on the right arm negative electrode on the left arm and creates a positive electrode here on the left leg and again if you imagine kind of the null electrode would form where somewhere in the center between those two directed towards that positive electrode in this direction here and so it would be like this positive electrode is the eye looking at the heart from below that already kind of tells you what we need to know the next part what portion of the heart do these leads tell us about are they really are good at so take a look here if you imagine avr it's kind of like a positive charge kind of situated like right here and it's looking at the heart kind of down this way it really is good at telling us about two parts of the heart the one part is it tells us about the very beginning part of the interventricular septum and it tells us about parts of the right ventricle as well so again what does avr tell us about it tells us about the activity of the right ventricle and what's called the basal septum okie dokie so that would be four let's write that up here this is for a v r the next one here is for avl avl where is the i kind of situated the i is situated right over here right so the positive charge would be here kind of looking down at the heart this way so that's going to tell us about what part here well if you can kind of follow this down here it's going to tell us kind of about the same thing that one did do you remember what one told us about that high lateral wall of the left ventricle it's the same thing for avl so avl will tell us about what avl will tell us about the high lateral wall of the left ventricle okay and last but not least is avf avf is going to be again imagine the eyeball is on the bottom so you're going to have the positive charge and it's looking upwards at the heart what part does that hit if you kind of draw an imaginary line you're going to get kind of this portion here what's this portion we already kind of seen this before it's going to kind of hit like from here to here do you remember what that looked like before with the limb leads leads two and three so leads 2 and 3 and avf tell us about the inferior wall okay of the heart so this is going to be about inferior wall of heart so if we were to combine some of these to kind of tell us about what we know already we can add on to help us to remember all of this in one thing not in separate pieces right so we know that avf sees the inferior wall of the heart but what else sees the inferior wall of the heart or kind of gives us an idea of what's going on with the inferior wall of the heart you can add on two three navf that's going to tell us about the infrared heart we already know that though and then again what tells us about that high lateral wall of the left ventricle avl but remember what else told us about it one so one and avl tell us about the high lateral wall of the left ventricle two three a vaf tells about the inferior wall of the heart and avr is just kind of like a lone rider that tells us about the right ventricle in the basal septum all right let's go to the next part now that we got limb leads down we got augmented unipolar limb leads down we know now that all of the limb leads are having uh upright kind of direction we know that all the augmented except for avr have all of an upright direction and we now appreciate the portions of the heart that those leads tell us about now let's do the same thing for the precordial leads all right engineers so now at this point in time we've covered our limb leads we've covered our augmented unipolar limb leads and we've talked about a lot of these deflections and what their ekgs should look like what portions of the heart these leads tell us about we're going to do the same thing for the precordials now the precordial leads are probably one of the more important leads out of all of the 12 limb leads because they can tell us a lot about pathology okay these are interesting ones so these are unipolar limb leads so they only have one kind of positive electrode that we put on the chest at different portions so these are unipolar leads and we put them on the chest at different regions so let's actually kind of annotate where those ones would go all right first thing here you put one of these v1 we call it the first one which again is a positive electrode all of them will have a positive electrode that we place on the chest wall v1 we actually go to the sternal angle okay that's usually around the second intercostal space and you feel down you go to about the right fourth intercostal space and that's where you'll put v1 okay then you go to the next one so go back over to the left side and you go to the left fourth intercostal space parasternal line that's going to be v2 you skip v3 for a second because you come back to him a little bit later then you go to v4 v4 you go down to the fifth intercostal space on the left and you go to about mid clavicular line you place v4 there v5 you stay in the left fifth intercostal space but you move to the anterior axillary line which is about right here okay so that's going to be v5 and the last one is you again stay in that left fifth intercostal space but keep moving moving moving until you get into the middle of the armpit and that's called mid axillary line so that's v6 now we got to come back though and place v3 where do we place v3 we just make sure it fits between somewhere between v2 which is that left fourth intercostal space parasternal angle or parasternal region between v4 which was left fifth intercostal space made clavicular lines so as long as you just place it between them it doesn't really matter so that's v three okay so these are our precordial or chest leads we know kind of now where they go right right fourth left fourth both parasternal this one goes between v2 to v4 v4 is left fifth mid clavicular v5 left fifth anterior axillary line v6 left fifth mid axillary line we know that these are unipolar they only have a positive electrode that we place on the chest so they only can pick up kind of the vectors that are moving either towards them or away from them and what plane that's what's really important this is what's really cool about them so they tell us about the electrical activity and what's called a horizontal or kind of a transverse plane which is very very cool so what we did here is we took a cross section okay of the thorax to where you're going to see the heart you can't obviously this is where your lungs would be here on the sides but we're taking a kind of a cross-section or transverse section of the thorax and looking at it now these leads we kind of try to have them all converge on a point here like that av node basal septal portion but each one of these tells us about a particular portion of the heart before we start getting into that though we should have an understanding very very importantly about the what's called the progression of the r wave and the s wave as we go from v one all the way to v six i'm not too concerned about the p and t's i'm very it's very important we understand the r wave progression as well as the s wave as we go from v one to v six when you talk about the ekg right so if we were to kind of just draw out the ekg waveform we kind of know all the parts by now uh definitely it's it's it's we're good at it now p wave q r s t wave there's two waves that i primarily want us to focus on throughout the process here that's the r wave and the s wave that's the ones i want us to really really discuss about the reason why is that q waves sometimes you see them sometimes you don't and really you shouldn't really see them at least big ones and v1 to v3 so again we're going to focus primarily on the r wave and the s wave and the ratio as you go from v1 to v6 very very important we have to understand this as a basic concept of ekgs so remember the first positive deflection in the qrs is the r wave the second deflection if it comes after whatever any positive deflection that is going to be the s wave so let's say that we take here and we kind of look at the ventricles i like to look at them a little bit separately with respect to the r wave if you think about it remember whenever the ventricles are depolarizing right we're at this phase you create a small right ventricular vector for the r wave and you create a large ventricular vector a bigger one for the left ventricle right and you know that you would create a mean one that would be a little bit more directed between the two of them but it would definitely be leaning more towards that larger left ventricular array vector for right now before we even look at the mean one i like to look at just the individual ones i think it helps me to make sense of this so let's look at that v1 if you kind of follow the lines here you obviously can tell that v1 tells us about the right ventricle v2 tells us about the right ventricle v3 it does a little bit of a right ventricle as well but v1 v2 v3 they should tell us a little bit about that right ventricle but primarily v1 and v2 so if that's the case then if i have a r wave vector that's coming from that right ventricle and it's little because it's not going to be as big as the left ventricular one because of the thickness what kind of r wave would i get for v1 v2 and maybe even v3 would i get a big r wave or when i get like a smaller r wave i get a smaller r wave right because that's a smaller r wave vector so if that's the case then my first upward deflection has to be little right like this and then like this and then like maybe a little bit maybe a little bit bigger as you go to v3 because look where v3 is starting to kind of look at it's starting to get more towards that left ventricle so if you kind of look at it v1 v2 may be the same size but v3 that that r wave should be getting a little bit bigger at that point in time okay let's keep following that over here to v4 and v4 is actually what's called our transition point because now we have that leftward kind of vector here that left ventricular r wave vector that's pointing towards the left side here and v4 is getting a good shot of it v5 is getting a really good shot and so is v6 so what do you think should the r wave be big for 4 5 and 6 or should it be small well that's a big r wave vector coming from the left ventricle so it should be a big r wave right so guess what we do we get a nice r wave even bigger here in v5 and then a decent size one here in v6 right actually don't need that yet we're going to get to the s wave in a second but you get the point here look at what's happening with the r waves as we go from v1 to v6 for the most part they should be getting smaller a little bit bigger a little bit bigger bigger bigger that's kind of the whole process of the r wave as you start to transition throughout these let's do the same thing but with the s wave so the s wave is usually indicating what so you're going to have this kind of depolarization of the bases and then this kind of depolarization of the bases as well same thing if you're kind of looking at these it's the same kind of concept here right that these are moving away from the positive electrodes okay so this is what happens is it's moving away from the positive electrodes so this will produce a downward deflection okay because again if you're looking at this one here it's going to be moving again away from the positive electrode that should produce a downward deflection if you look in v2 same thing it should produce a downward deflection and v3 it should produce a downward deflection but guess what that downward deflection starts to decrease as you move from v3 all the way to v6 so now watch what happens now this should kind of become a like a little bit smaller look a little bit there and then here this one will kind of almost become like isoelectric this one will be really tiny and this will kind of be almost non-existent so do you see what's happening now with the r to s ratio here is that as you progress the r wave should be getting bigger as you go from v1 to v6 and the s wave should be getting smaller as you go from v1 to v6 that's very very important especially when we start talking about axis deviation and other types of pathologies like ventricular hypertrophy so on and so forth okay so again what do i want you to get out of this r wave progression as you go from v1 to v6 what happens to the r wave it should get bigger as you follow the s wave from v1 to v6 what should happen it should get smaller okay that's very important to remember all right so i think we now have a pretty good idea of what the rds ratio should look like through v1 to v6 and what these kind of pre-coordinate leads are telling us about all right so now at this point in time we should have a pretty strong idea about where do we place the precordial chest leads right we should understand what kind of a way they're looking at the heart from a horizontal or transverse plane we should very very importantly understand the progression of the r wave as we go from v to 1 to v to 6 is increasing and that the s wave as we go from v 1 to v 6 is decreasing so the r to s ratios usually less than 1 for v 1 to v 3 greater than 1 for v 5 to v 6. and the next thing that we need to understand here is what portions of the heart do v1 all the way to v6 tell us about because that's very important again when it comes to stemis so to make it easy there's the different parts that we're going to color in here for us right so this first one here right ventricle right ventricle is definitely going to be told to us by v1 v2 and even a little bit of v3 so i want you to remember here v1 to v3 will tell us about the activity of what it'll tell us about the activity of the right ventricle now do you guys remember what other lead that we talked about like the limb leads or augmented unipolar limb leads tell us about the right ventricle which one avr so avr you can also add into this if you want to also gives us an idea about that right ventricle pretty cool right so if you wanted to add in from what we remember you can also add in there a vr like we did before all right so we know that v1 to v3 and we can add on that little avr there as well to help us remember stuff recognition there that that kind of tells us a little bit about the right ventricle now the basal septum though the top part of the interventricular septum if you will that is going to be pretty much picked up by the active by the electrodes v2 and v3 so v2 to v3 tell us about that basal septum but what else told us about the basal septum remember avr told us about the right ventricle and the basal septum so if we want to we can also add in avr okay let's go over to the next part so now we have the anterior portion of the heart so the anterior wall of the heart so the anterior wall of the heart is a very good big chunk of the heart and that's going to be from v2 all the way to v4 so v2 to v4 tell us about the anterior wall of the heart very very important one okay the last one here which is going to be telling us about the kind of the lateral wall of the left ventricle so again which part of the left ventricle here the lateral wall of the lv which is your left ventricle that's going to be what v5 and v6 which will be giving us a good representation of that part of the heart so v5 to v6 now if you wanted to add on here and think a little bit about this remember the lateral wall of the left ventricle is v5 to v6 but do you remember what kind of the higher part of the left lateral wall of the the ladder wall of the left ventricle was covered by one in avl so sometimes if some people develop stemis and v5 v6 they may also they have elevations in v5 and v6 they may also have some elevations in one in avl if it's those higher parts so sometimes you can also combine one avl v5 and v6 together because they really give you a good idea about that entire lateral wall of the left ventricle okay all right i think we have a pretty good idea now about these precordial leads and i think we have a pretty good idea about all of these different waveforms and vectors and physics which i know is my numbing sometimes what i want us to do is now start taking everything all this basics kind of topics that we've gone over and start applying that to ekgs now what i really want to do is give you the very basics about what an ekg kind of strip or paper looks like what are some of the bare minimum things that you really need to know whenever we start reading them and then also talk about a quick little recap of the uh different deflections and maybe what the actual parameters or distance of those intervals or waves what how wide they should be how long they should be so on and so forth so let's now come over here finish off our lecture with that all right so we've really built up our foundation now we have a very strong foundation that we've built let's go ahead and really quickly before we really start getting into looking at lectures and reading real ekgs have a basic idea of some of the components of the ekg strip itself so if i were to take here i want you guys to know first thing you see this big large red box this big large kind of red box right here there's a couple things i want you to know about it's a large box first thing i want you to know is i want you to know a couple things about its width less significant with respect to these i want you to know the height so the width and the height thankfully are the same it's five millimeters and with five millimeters in height you're probably like okay what the heck is that supposed to mean i'll tell you don't worry width is a little bit more of the important one okay so i like to turn with particularly in because this is measured over time so width is really helpful when it comes to time height is determining kind of the amplitude or the voltage that the wave is actually kind of generating so the more dependent upon the voltage or the amplitude so when it comes to width i look at that with respect to time so i want i need to have some kind of conversion factor if you will between five millimeters and some type of seconds or milliseconds i like seconds so what actually it happens here is five millimeters is actually equal to 0.20 seconds so one large box means that 0.20 seconds has gone by with some electrical activity that's occur occurred right there on the ekg strip height wise that's five millimeters right so five millimeters tells us a little bit about the voltage like i told you so voltage for this is generally going to be about 0.5 millivolts so 0.5 millivolts is how much 5 millimeters is equal to so one large box in height tells us that there is a voltage of about 0.5 millivolts is that important not necessarily we'll see later that sometimes you can have low qrs voltages in certain conditions but the real important one that i really want you to remember i think it's very important to remember is the width because that's going to become very significant when we start talking about is the pr interval too long is it too short is the qt interval too long is the um is another thing is the qrs waves wide are they narrow so on and so forth the next thing is if you look in these large boxes there is so many small boxes and you know how many there is so within one large box there's actually equivalent to 25 small boxes okay so there's kind of like five rows five in each one so it's kind of like if you want to think about it's five millimeters squared uh for these actual the small boxes okay so when we talk about the small boxes what i really want you to know is the same thing i want you to know with important and i want you to know height so for the small boxes the width is actually very interesting here you think about it one two three four five five little boxes pick up one large box it's five millimeters in in width what do you think the the width with a small box will be one millimeter so it's one millimeter then if you take five and divide it from so you take .20 and you divide it by five that'll give you your time that it takes for that one small box and that's equal to about 0.04 seconds also very important okay now height same thing it's equal to one millimeter which is equal to 0.01 millivolt right because it's the same thing it's just off by a factor of in this case it's off by a factor of uh 10. okay so what do i really want you to know about the height stuff i'm not really concerned about you knowing the millivoltages i'm more concerned about you knowing that one small box is one millimeter one large box is five millimeters the reason why is when we have to measure st segments is the st segment elevated well sometimes it needs to be one millimeter elevation so you have to go in and see is the sd segment elevated more than one box or maybe it's super elevated and you see an st segment that has elevation beyond one large box five millimeters so the whole point is why do i really want you to know the height not super important for the voltages more important for measuring those st segments okay that's the basic concept if you really wanted to know a little bit more so again width is the big one height is going to be a little bit more it's you know particular for the small boxes the one millimeter hopefully you don't see st segments that are beyond five millimeters in elevation but again you can but again i think we have a basic concept of that the other thing i want you guys to know about this is whenever we look at this ekg we see the various waves right we already kind of have a pretty strong idea about these but if we were to quickly recap this is our p wave q r s st segment and our t wave right same thing but now let's talk about maybe some extra stuff this is our p r interval this from this point here to this point here is our q t interval and then this part here is our st segment right and we already kind of talked a little bit about that sd segment there but what i really want you to know is that these are going to become very important in certain types of pathologies okay so i want you to have a basic idea of some of these so the first one that i want you to remember is your pr interval so your pr interval we already kind of talked a little bit about that it's from the beginning of the p wave all the way until we get to the beginning of the qrs complex right a pr interval should normally be from it should be less than 0.20 seconds so it should be less than one large box that's kind of the goal if it's less than 0.20 seconds it's considered to be a normal pr interval if it's greater than that it's prolonged it's going to become important in different types of blocks okay so this is considered to be normal the next one that i want you to remember is your qrs complex so your r s the width of that usually you want that to be less than 0.12 seconds okay which if you count that up one little box is 0.04 seconds so if i do 0.04 times 3 that's 0.12 seconds so i want it to be less than three little boxes if it's greater than that it's considered to be a wide qrs a pathologically yqs now some textbooks will even go and be a little bit like in stingy and they'll even say technically like greater than .10 seconds is considered to be a little bit wider of a qrs but it's easier to remember and for the sake of it if you're starting to like question it is it wide is it narrow you're taking too much time if it's greater than 0.12 seconds three little boxes it's wide if it's less than that it's narrow don't make it too complicated right so this is going to be normal or sometimes what we call you'll see us refer to it a lot kind of they're synonymous in a way they're kind of referred to as narrow which is normal all right the last one here is the qt interval that i want you to know so the qt interval is important because whenever that sucker is prolonged it increases the risk of a particular type of arrhythmia called torsades to points which is a type of polymorphic vtec and so this number it literally it can vary from textbook to textbook it can vary from gender to gender so male females there can be a lot of different ones the reg consensus that's kind of been i've seen here within the textbooks that i utilized was that if you're a a male or a female and if it's a male less than 430 milliseconds now this is utilizing rates particularly at like 60. it depends if you're going a little bit faster you have to adjust and we'll talk about those things later you have to use like corrected qtc formulas and we'll get into all that stuff but for the most part less than 430 milliseconds is considered to be normal in males and then less than 460 milliseconds in females is considered to be normal now again i don't want you to get too bogged down into that detail i usually don't consider something to be super dangerously like prolonged qt until i start approaching 500 but again to really kind of be thorough these are the numbers that are generally thrown around but we'll talk about this a lot more when we get into the arrhythmias okay [Music] you