all right you guys welcome back to the last lesson in a series of lessons covering ECG and EKG rhythm interpretation and in this last lesson we're gonna cover the heart blocks [Music] [Music] oh right you guys welcome back and congratulations on making it to the last lesson in this series of lessons on ECG and EKG rhythm interpretation like I said in this lesson we're gonna cover the various different types of heart blocks that you're gonna find your patient in for those of you who don't know my name is Eddie Watson and I'm gonna be your presenter for this lesson and if this is your first time to this channel and watching one of our videos and you'd really be interested in seeing more in-depth critical care educational content such as this we invite you to subscribe to our channel below if you do make sure and hit that Bell icon and select all notifications this way you'll get notified as soon as our lessons become available to you guys your support truly does mean a lot to us and you guys really help support our channel and videos such as this and so for that we truly are thankful all right so let's go ahead and get into it and so to start out heart blocks they're basically what they sound like there's some sort of block in the impulse that's gonna cause some sort of arrhythmia in your patient there are several different types of these and we're gonna go through and cover each of them pretty extensively here but to start us out I want to talk about our bundle branch blocks so essentially what's happening with our bundle branch blocks is that we have one of the bundle branch pathways that is blocked and is not allowing for that high-speed signal to get to that side of the heart and so this causes the depolarization to move very slowly across that ventricle and there's primarily two types of bundle branch blocks that we're gonna worry about we have our left bundle branch block and our right bundle branch block now we're going to talk about each of these here and causes and how you would identify them but ideally you're gonna want a 12-lead in order to truly identify and diagnose a bundle branch block but you are able to recognize these as well just on your normal bedside monitor because they're gonna manifest themselves as a wide QRS complex with some sort of difference in telltale sign that will really help you to identify as in a left or a right bundle branch block now in all the past examples we've talked about using lead 2 as our lead to be analyzing and interpreting these rhythms but specifically if you're suspecting a bundle branch block you want to be looking at your V lead on the monitor which is gonna line up with what is the v1 lead on a 12 lead EKG so for the first of these we're gonna talk about our right bundle branch block and when we're looking at the V lead on our ECG we're gonna see something that looks kind of like either this or perhaps something like this and so basically what's happening here is because that right ventricle is having to depolarize slowly you're gonna end up with a very quick left-sided depolarization that shows up in the middle of your right ventricle depolarizing so in this first example we've got the left side depolarization happening here while this entire thing is the right-sided depolarization whereas in this other example here we have our left-sided depolarization all within our right-sided depolarization and so these right bundle branch blocks can really be caused by a few different things you can have things affecting the the right heart these can be things like pulmonary hypertension valvular disease PE etc can also be the result of conduction system degeneration can also be are the result of coronary artery disease or CA D and this can be either acute or chronic or it can be from other causes and these are going to be things like drugs electrolytes Baron sees things of that nature but the way that we're gonna distinguish this right bundle branch block from the left bundle branch block which we're going to talk about in a second here is in our v1 lead we're gonna have what we call terminal positive and essentially what that saying is the last part of the QRS complex before we go back to our isoelectric line and on to our T wave if we have a positive part to it then we can identify this as a right bundle branch block so even though we go up and down here we end up back up again before we come to the isoelectric line meaning that last part of it was on the positive side of that line and the same with on this side where we went up crossed back down but came back up again at the end before we came back down to that isoelectric line so you want to pay attention that last part of the QRS complex if that last part was positive then you've got a right bundle branch block so now moving on to the left bundle branch block you're gonna end up with something that looks like this so definitely a bit different than what we see in the right bundle branch block but you might not be able to pinpoint exactly what it is that's different that will be your tell-tale sign perhaps maybe you do and if you do awesome job now with our left bundle branch block there again are many causes of this the first can be something like a cardiomyopathy it can be from either valvular or hypertensive heart disease again coronary artery disease can be a cause either acute or chronic and again the same conduction system degeneration now when we talk about identifying the left bundle branch as opposed to the right bundle branch again we're gonna be looking at our v1 lead but this time we're gonna have terminal negative and again what that means is before we come back to our isoelectric line if the last part of our QRS complex was a negative deflection then we've got a left bundle branch block and so again we can see in this example we go up and then down before coming back up again the last part was down here negative therefore we know this is a left bundle branch block and again like I said it's important that you guys are looking at your vee lead as opposed to lead to in order to truly be able to distinguish either a left or right bundle branch block and so that's about all I'm gonna really cover on these bundle branch blocks I did want to include them as they are technically fall within that category of being a heart block but moving on from there we're going to go ahead and bring up again our six second strip for our EKG paper and for these last remaining heart blocks we're gonna give you examples on here just like we did in the previous lesson and so now these blocks that we're going to talk about fall within a category of what we call our AV blocks and these are going to be the typical heart blocks that you guys are gonna encounter and have to be able to identify now these blocks are the ones that oftentimes will cause people trouble when they're trying to analyze these rhythms they definitely can be difficult but hopefully by the end of this lesson you guys will be able to better understand these and understand what's happening and truly be able to identify each of them the thing to really keep an eye out here is the regularity of the P waves and then our waves of the QRS complex it's going to be really important that you guys are measuring the PR interval which we talked about in the second lesson in this series in order to truly be able to recognize these so with that said let's go ahead and move on to the first of these AV blocks which just so happens to coincidentally be our first-degree AV block and so to start out what's happening in a first-degree block is we're having a prolonged transition of impulse through the AV Junction so as we talked about the job of that AV node is to delay that transmission of that impulse but if it happens to delay that impulse too long then you end up with a first degree heart block so let's just go ahead and list out some of the defining characteristics of a first degree block and then we'll talk about what we see on the rhythm strip here the first of these is going to be that you're going to have a PR interval that's greater than point to zero and with that you're gonna have regular P waves and regular R waves and along with that you're gonna end up with a narrow QRS so let's go ahead and take a look at our rhythm here and see what we've got going on so first off we can definitely see we've got a narrow QRS here so check that one off then if we take a look at our P wave if we were to measure out this PR interval which goes from here to here hopefully it's pretty obvious in this example but we definitely have a PR interval that is well over 0.2 0 seconds as you can see we go across one big box and almost another 5 smaller boxes so we are definitely elongated here so if you think about that impulses initiating and that sa node and it's going to the AV node and it's taking a while and then finally you have your QRS complex in which that impulses pass down the bundle of hiss now in addition to that if we check our P waves we can see that these P waves march out pretty regularly in addition to that our our waves also march out pretty regular therefore we've got our regular P and our regular R with an elongated PR interval greater than 0.2 zero seconds with that narrow QRS therefore we know that this is a first degree heart block now I'm gonna start off with a little analogy that I've got to give credit where credit is due this comes from Laura guess Paris and her CCRN review but she explains these heart blocks as an example of a husband and a wife and what's happening in a first-degree block is the husband comes home late and in this example the husband's the p-wave and the wife is the qrs and in the first degree heart block we see we have the husband who comes home every single night but he's late and he's late every single time he's consistently late but he comes home and therefore every single time you've got a P wave and a QRS just with that elongated PR interval all right so let's go ahead and move on to the neck of these AV blocks and for this this is going to be our second-degree heart block and this is going to be specifically the mobitz type one or what you'll hear commonly referred to as a Winky Bock and so what's happening with a Winky Bock is you've got this cyclical and progressive conduction delay through the AV Junction so that problem is occurring in the AV node which still happens to be susceptible to the parasympathetic response and so what happens is you get this cyclical prolongation of that PR interval followed by what we call a dropped QRS which is essentially a P wave without a QRS complex so to go over our defining characteristics we're going to have that cyclical prolongation of that PR interval and again that's going to be followed by a dropped QRS and I will explain that in a minute so that it makes sense for you guys with this you're gonna notice irregular qrs's but still you're gonna have that narrow QRS and just to cover some of our potential causes of this it could be as a result of increased vagal tone could be from myocardial ischemia or it could be from the effect of drugs think of things like our calcium channel or beta blockers or even digoxin now I did also forget to mention real quick along with that irregular QRS you're also gonna have in a regular P so let's take a look at this and see what we have going on so first if we look at our first beat that we have here we've got what appears to be a normal PR interval as well you've got that normal QRS complex but as we go on to this next beat here we can see that that PR interval has gotten longer and again if we go on to this next one we see that that PR interval is even longer until finally we have this lonely P wave and no QRS complex where the heck did it go well this is what we call that dropped QRS so we had that cyclical prolongation of the PR interval so that conduction of that signal became longer and longer and longer until eventually we dropped it and we no longer passed that signal through therefore you don't end up with a QRS complex and then just like clockwork things restart back again and we end up with a short and then a longer and if we kept going on you would see a longer before another dropped beat now it's a little bit hard in this example to identify some of the irregularity and the P wave so it definitely would be helpful to have that piece of paper or a note card with you but we do have irregularity in these P waves they're not coming at a regular frequency and definitely hopefully with these QRS is you can certainly see the irregularity as this and this are quite a bit different now to take it back to the husband-and-wife reference in this example we've got the husband who first comes home normal then he comes home a little bit later and then next night he comes home a little bit later until finally the last night he just doesn't even come home and that's essentially what's happening as we have that PR interval that gets longer and longer and longer and finally it just doesn't get through and so with these second-degree AV blocks there's actually another one on mobitz to which we're going to cover in a second here but one of the ways to help you really remember that this is a winky Bock is there's a little phrase that you can say that actually a friend of mine taught me way back in nursing school that has really kind of stuck with me and it's longer longer longer drop then you have a winky balk so it's got a nice little ring to it hopefully that'll help you guys remember that when you have this going on this is a winky Bach or a mobitz one all right so moving on I already pretty much alluded to what's coming up next and that's gonna be our other second-degree block which is a mobitz type 2 now this one doesn't have a fancy name like the winky Bock so you just have to remember if it's not a winky Bock its type 2 but this is an example of it here essentially what's happening in a mobitz too is we have some sort of intermittent block that happens below the AV node so it's not going to be a cyclical thing like we saw with the mo bits one or the Winky Bock and this problem is actually occurring below the AV node so somewhere in that top portion of the bundle of His and therefore we don't have input from our parasympathetic fibers some of our defining characteristics for a mobitz - or you're going to have a fixed PR interval you're still gonna have a narrow QRS but you're gonna have occasional dropped beats and for this one you're gonna end up with regular P waves but irregular R waves but an important thing with this rhythm Before we jump into really kind of explaining this is this one's going to really require close monitoring and the reason for this is depending on how frequently we're having these dropped beats we have the potential to have a low cardiac output as a result of that and even more concerning is while this is an incomplete or an intermittent block it could progress into a complete heart block which we are going to talk about next so here kind of looking at our rhythm strip if we look at our examples in our first beat we've got a normal PR here we've got another normal PR here we've got another normal PR but then all of a sudden we have this lonely P wave without a QRS complex therefore this is one of our dropped beats again we've got our normal QRS is here and if you think about what's happening here is we have this signal which is originating in the SA node and most of the time it reaches the AV node goes through the normal delay and gets passed right along but every so often we run into a problem and that signal or that impulse just does not get passed along and that's where we end up having these random dropped beats now again if these are happening every so often you're not going to see much impact on your cardiac output but if you start having a lot of these drop beats well you're gonna be drastically reducing your heart rate and thus drastically reducing your cardiac output so here we kind of talked about our fixed PR intervals our narrow QRS having our occasional dropped beats and then if you look at our P waves you can see that these just march right along at a regular rate and some of them get through and some of don't whereas if we look at our our waves we can definitely see we've got some irregularity based on these wide differences we see here and so with all these criteria met we know that this would be a second-degree heart block mobitz type 2 and again to go back to our husband-and-wife analogy in this analogy essentially sometimes the husband comes home and sometimes he doesn't when he does come home though he always comes home at the same time but occasionally he just doesn't come home alright and so now to move on to the last of these heart blocks this is going to be what we call a third-degree AV block or a complete heart block and so just as the name suggests that this results from the complete block of impulse from the AV node to the ventricles an important thing to know when you have a patient that goes into a complete heart block as this is often going to result in hemodynamic compromise and so really to kind of explain what's happening here is we do have an impulse that's originating in the SA node and it's firing along and it's all happening at a pretty regular rate but absolutely none of those are making it through to the ventricle and so the ventricle has had to pick up its own intrinsic rate in order to provide some sort of cardiac output but which oftentimes is not going to be sufficient for your patient and so you're gonna just see these lonely P waves just marching out regularly but no real Associated QRS complex and so this is going to lead to a chaotic PR interval now along with that you have the ventricle which is picked up its own intrinsic rate and so that's going to be marching along pretty regularly but instead of that normal narrow QRS is we're going to have that wide QRS so again think about those ventricular rhythms or on the PVC that's what you're gonna see here and so with this you're gonna have regular p-waves and regular are waves but they're just gonna be going on and doing their own thing and not having any kind of communication with each other like I said due to that decreased cardiac output and that hemodynamic compromise this is often going to require some sort of immediate intervention typically pacing so if we take a look at our rhythm we're gonna look for our P waves and see if we can find them all so here we have one here we also have one that gets buried in that QRS here's another one here's another one this one's kind of buried within that QRS another one another one another one and another one so if you look these dots March themselves out pretty nicely so we do have those regular P waves happening but if we take a look at our PR interval here we've got a really long one here we've got a kind of long one here's a short one over here would be the start of another really long one so we really just have that chaotic PR interval that just doesn't seem to be making any sense in addition to that we do have that wide QRS complex here which should help to be a telltale sign that you've got some sort of complete heart block going on here and as well we do have our our waves which are marching along nicely here so we had that chaotic PR interval wide QRS and regular P and regular R but as you can see they're just doing their own thing and each one is just doing what they need to do and not having any kind of communication with each other and to bring this back to our husband-and-wife reference that's exactly what would be happening here is the husband and wife are just doing their own thing coming and going at their own schedule without any interaction with each other all right and so that is going to conclude our talk here on the various different heart blocks like I said I know these ones can be tricky to identify but if you really kind of think about some of those criteria that we talked about each one of these has a pretty unique set of criteria so if you just think through what you're seeing and take your time with it I promise you that you guys can figure this out and so with concluding that that's also going to conclude this last lesson in this series on ECG and EKG rhythm interpretation hopefully going through these four lessons has really helped to build a solid foundation for you guys because it's an essential ability that you have to have and working in the ICU and being able to look at your patient's rhythm and identify what's going on because sometimes these interventions require immediate action again down in the comments I'm gonna link to a couple resources one of those is what we call six-second ECG which is a really great online learning resource that goes through different arrhythmias and heart blocks and as you try to identify them and really being able to understand these is just gonna come from repeatedly practicing these over and over until you get good at it but eventually if you do this and you put the time in you will reach a point to where you can just look at these and pretty quickly be able to interpret these rhythms and there will be much less stressful when you actually see them happening in real life - of course the identification of some of these rhythms which mean that your patient as well as you are about to be having a pretty bad day all right and so with that said I truly want to thank you guys for watching hopefully you guys stuck with me through these four lessons and you've been able to develop a good strong foundation and your ECG interpretation if you found this lesson or the other ones to be helpful to you please go down and leave us a like as well as leave us a comment I really truly enjoy hearing some of the feedback that you guys give and I'd love to hear that you found these lessons useful and if you haven't already make sure and subscribe to our channel below that way you'll be notified when the next lesson in our next series that we're going to begin becomes available in the meantime make sure and check out a couple of our other series of lessons we've got one covering arterial blood gases as well as another pretty complex series of lessons covering shock and as always thank you guys so much for watching you have a great day