 What's up YouTube? Dr. Ali Hader here. Thanks for checking back into the channel. Today's video We're going to be talking about heart blocks going through the different 80 blocks and some bundle branch blocks as well And hopefully you guys get something out of it So if you like what you see hit the like button, please subscribe to the channel and share with your friends All right guys, so we're gonna dive into it We're gonna be talking today about various types of heart block. Okay, heart block basically refers to Abnormality in conduction tissue somewhere along the lines of the heart that is causing either slowing or Blocking of conduction through a specific pathway Okay, and this can occur on various levels and we're gonna kind of go through all the basics and the salient features here Okay, so if you saw my first EKG video, you remember this diagram Which is sort of representing the heart's conduction tissue. Okay up here again is the sinoatrial node at number one This fires and sends signals across the atrium, which is number two Entering the AV node at number three the AV node will subsequently send Conduction down to the bundle of his which is the important structure below the AV node Which will subsequently send the signals down the two bundles the left bundle and the right bundle to Depolarize the ventricle so essentially heart block can occur at any point along these pathways So let's dive into it again The first area that starts the cardiac cycle is again the sinoatrial node So if there's a problem in the firing of the sinoatrial node, that's called six sinus syndrome or sinus node dysfunction Not really heart block because it's more of an initial abnormality of the initiation of the signal and not blocking of a conduction path Now if there's a problem with the signal actually exiting the sinoatrial node into the atria that is referred to as Sinoatrial exit block Okay, so that means the sinus node is firing. However, the signal is not Manifesting itself within the atrium because there is an abnormality of the conduction leaving the Sinoatrial node We'll talk a little bit about that later. That's probably the least important of the blocks. I would say Now if there is an abnormality of conduction through the AV node That's when we start getting into our more common types of block. So at number three we're going to see first-degree AV block Again within the AV node or Second-degree AV block Mobits one Which is a wanky block block again, this is due to high vagal tone and It usually is the less serious in terms of AV blocks So those are two types of block that we're going to see within the level of the AV node And these are again often influenced by high vagal tone medications, etc Now when we're getting down to the hits, this is when we're starting to see more of our advanced blocks So when we talk about block below the AV node or block below the his we're talking about more advanced types of heart block Okay, so that's when we're going to be seeing the second-degree AV block mobits two Okay, or third-degree block Essentially, these insinuate more advanced block again anything kind of below this level All right, which means that there is a much poorer backup system that the heart has to kind of compensate for that block And these are the ones that can lead to a systole and often require a pacemaker. Okay Now down here in the bundles again normal conduction should go equally down the left bundle and its various fascicles, okay, there is the left posterior fascicle here and the left anterior fascicle here and of course the right bundle which has its own fascicle and Conduction should go down equally down these both pathways to cause uniform depolarization Now, of course, there can be blocked in any of these bundles individually and that can lead to either a left bundle branch block or a right bundle branch block The left bundle can also have block within each fascicle the left anterior fascicle Causing the left anterior fascicular block or a left posterior fascicular block So Basically, these are all the areas And the classifications of heart block and our job is to kind of figure out on the EKG Where this is occurring and to figure out is this something more concerning like somewhere within here? Or is there something less concerning like up in the AB node or just sort of in the fascicle? And again down here in number five these are going to be blocks that are manifested within the QRS Whereas everything else is sort of manifested In the PR interval. So now that you have a basic understanding of what's going on Let's take a look at what to look for on the EKG tracings for these blocks. All right So let's dive into it and here we're going to kind of go over What exactly we're going to be looking for on the 12 lead EKG and on telemetry when we're trying to make the diagnoses of these Various blocks, so we're going to start with first degree of the block if you recall this occurs at number three here in the AV node This is pretty simple. What we're going to be looking for here is a simple prolongation of the PR interval So you have a P wave and you have your QRS and The PR interval is greater than 200 milliseconds Whenever you see this that is a first-degree AV block You're not going to have any drop beats. You're going to have a consistent PR interval second-degree AV block mobits one also known as wankybock This is characterized by a progressive prolongation of the PR interval Where you're gonna have a P wave a QRS a P wave longer PR interval Progressive prolonging until you have a drop B. So you're gonna have progressive PR prolongation leading up to it and then eventually a dropped QRS All right, and this can be in cycles of four to three meaning four P waves of three QRS's and It can be three to two It can vary and sometimes you'll see a couple of wankybock cycles Amidst normal sinus rhythm. So make sure you take a look at all the tracings and the telemetry to make the diagnosis In second-degree AV block moments to this is block occurring below the AV node So at the level of the his or lower here, what we're going to see is P QRS and Eventually a drop beat without prolongation of the preceding PR intervals. All right so this is going to be a repetitive pattern with consistent PR intervals followed by drop beat in this example, we have a three to two Mobids two because you have three P waves for every two QRS's. All right and This can also vary between three to two two to one four to three etc and Again, the key is Steady PR intervals Now third-degree AV block also was occurring at the level of the his or lower Right here. What you're going to see here is complete AV dissociation. So you're going to have P waves That are doing their own thing and Amidst this you will have QRX complexes that are at their own rate Not doing anything that the P waves tell them. So there is complete AV dissociation all right where the ventricular rhythm is Doing its own thing based on its inherent escape rate. So Gotta look carefully. You can always get this confused with mobits, too I see it happen all the time But if you use your calipers and you are careful you'll be able to figure this out Oftentimes the QRS rate here is very slow. Look for what the escape rhythm is going to be. Is it wide? Is it narrow? This will give us an idea of where exactly the escape rhythm is coming from Obviously, if it's wide, this is more concerning and the patient can be more unstable Now briefly, which I'm going to talk about afterwards two to one AV block Can be tricky. This can technically be either a mobits one or a mobits two And we'll talk a little bit about this in a minute Now let's look at the bundle branches and the fascicles Again, these are going to be abnormalities of the QRS complex You can get individual block of the fascicles So if you have a block in the anterior fascicle left anterior fascicle, which is here what you're going to see is a Positive deflection in lead one you'll have a negative deflection in lead two and often you'll have a mini QA in lead ABL this negative lead two pushes the vector towards a left axis and Oftentimes you're going to see the QRS duration is going to be Between 100 and 120 milliseconds because there is some degree of conduction delay here In the left post your fascicular block What you're going to see is the opposite Where lead one the vector is negative in lead two you'll get a positive vector and This is again indicative of isolated left post your fascicular block This is much less common than a left anterior fascicular block, but you may see it from time to time Moving on to a left bundle. So if your entire left bundle upstream is blocked You will get a complete left bundle match block now You're going to see a QRS duration of greater than 120 milliseconds And how you're going to distinguish that between the left bundle and right bundle is really looking at two leads lead v1 and v6 In lead v1 a left bundle is going to give you a QS complex All right, so you're going to have a QS complex You're not going to have an R wave here and it's going to be broad and it's going to be wide And it's essentially just one big QA lead v6 is sort of the opposite you're going to get Sort of this RS complex where you're going to get a broad often a notched R wave indicative of the conduction delay a Right bundle on the other hand again greater than 120 milliseconds, but in the lead v1. It's going to be the opposite in this case you're going to get this RSR prime most of the time which is sort of like the quote bunny ears that we describe where you're going to have a notch and A delay on the R wave and in lead v6 what you're going to have is the slurred S wave All right This slurred S wave often got me confused What exactly it meant? Basically, this is occurring because most of the depolarization is rapid and early from the left side and the slurred S Represents the delayed depolarization occurring from the bundle branch the right bundle branch block All right, so again for these two bundles left and right if you notice it's greater than 120 milliseconds Look at these two leads and you'll be able to figure this out So real quick about two to one AV block two to one AV block is when you have two p-wave for every QRS So that means every other p-wave does not conduct a QRS and you get a drop B Okay, now this becomes Questionable about the level of block is it a moments one or a moments two Because there's every other beat that's dropped You don't have enough cycles to see could there be prolongation of the PR interval Okay, and it's tempted to call this moments two, but technically we can't be sure of that Now moments one is blocked in the AV node whereas moments two is below the AV node, right? So AV node block is due to high vagal tone. So if we can manipulate that this could help us out if we exercise the patient by walking them or doing some sit-ups this could Decrease vagal tone and improve our block if it's a moments one However, if the block were to worsen with exercise such as go from two to one to three to two This is more indicative of moments two in the end call it two to one AV block, but think about where the block could be Okay, so we're gonna go through a quick example here Here's a rhythm strip and we're gonna figure out what the type of block is here first thing to do identify the p-wave So we see p-waves here. Here's one the t-wave and their p-waves that are just sort of marching through here and Obviously, there's a lot less qrs All right, so there's more p-waves in qrs already indicative of some sort of block next Let's look at the p and the qrs relationships. Is there a relationship here? Here's our PR interval here Here's another one. Here's another one. All these are different and it does not appear that there's any potential Relationship here, right? So why don't we look at our pp interval now? So this is our p to p interval and we're gonna make sure all our p-waves are of the same cycle length and you can see They are which means the p-waves are firing at their own rate now if we look at the qrs Intervals all right, you'll notice that they are also firing at their own rate So we have two completely separate rhythms between the p's and the qrs with no relationship. What is this? This is third degree AV block