Hi again. We're back with dysriythmias and we're going to continue on with the next section called conduction abnormalities and this is talking about different types of heart blocks. We talk about conduction abnormalities. They're an inhibition of cardiac impulses along the conduction pathway. So somehow in different spots we know what the conduction pathway is. We have the electric impulse that begins in the SA node and as it travels through it gets blocked somehow. An example right here we'll talk about some of the causes and the different types of heart heart block. So there can be some congenital causes can be acquired CHF, MIS, um valve problems, anything that can kind of contribute to to um interference of the electrical conduction system. So we're going to talk about two main groups of heart blocks or conduction abnormalities. And the first one is called a bundle branch block, which is probably something that you've heard of. And you have to think about where the bundle branches are. So let's let me do this and kind of put this line across and show you where the the heart blocks are. So a bundle branch block is in the ventricles in the in the bundle branch. So for example, this one right here has a block in it. Maybe there was an MI in this part of the the septum became eskeemic and it interfered with the conduction and it doesn't work and and the the conduction can't get through. And this bundle branch block takes place in the ventricle because the the bundle branches are the reason that the ventricles are contracting. Correct? I think another term that I have down here in parenthesis is IVCD. IVCD stands for intra ventricular conduction delay. Okay. So, if we're just looking at a patient and the strips that we've been looking at, they're just a single strip uh looking at one lead. uh if we determine that there's a block in the ventricle, we really can't say that it's a bundle branch block because we don't know we don't know where the block is. The only way to tell if the block in the ventricle is in one of the bundles is with the 12 lead EKG. But there's a simple way to know that somewhere in the ventricle there is a conduction delay. So somewhere from the bundle of H down, there's a conduction delay and we call it an IVCD. When somebody has an IVCD, we get a 12 lead on them. And that we'll talk about that in the next section. And then we can determine if somebody has a a right bundle branch or a left bundle branch. We need a 12 lead to actually confirm it. So IVCDs, which include bundle branch blocks, are in the ventricle down here. And then the second one is AV blocks. An AV block is a block in the AV node right here. So this is where AV blocks are. And I didn't draw this line very well, I suppose. And then this and down here are where ventricular blocks are. So we're only going to talk about AV blocks and ventricular blocks. So know where they are. The AV block occurs in this AV node or this AV junction right here. And there's three degrees of blocks. A first degree, a second degree, and a third degree. First degree being mild, and third degree being severe. Okay. So, second degrees are considered more moderate, right? Sometimes people have symptoms, sometimes they don't. Mild and severe. So, when we talk about AV blocks, let me see here. Wait one second. When we talk about AV blocks, we're going to talk about the different levels. And I'll just I'll just wait till we get to the next picture to tell you. So, so that's with this slide. I just want you to know we're going to talk about two different types of blocks. And the next slide is going to show us a ventricular block or a intraventricular conduction delay. Like I said, very likely that it's a bundle, a right bundle or a left bundle branch block, but we can't diagnose the bundle branch without a 12week. So, we get the strip. It's on our patient and we start doing the steps. We take a look and we see the rate 1 2 3 4. Okay. And this probably another one right here. So, it's probably 50. And this might not even be a six-second strip, but just we'll just say that the rate is 50. So, it's a sinus brady. And we take a look and we measure and we can see that it is regular. Okay, so it is regular. We take a look at the Pwave. We see that there's a Pwave. It's the same shape and it's in front of the QRS. So those are two yeses. And then we want to do our measurements. And we measure the Pwave, the PR interval right here, the beginning of the P to the beginning of the QRS, which is kind of inside here. So 1 2 3 just a smidge under three boxes. So maybe one or.12 but regardless the PR interval wait 1 2 3.12 sorry it's 0.12 and so regardless it's normal. Okay. Then we want to measure the QRS complex. And we're measuring the QRS complex right here. We see an R and then this big gigantic wide Sway. So we have to measure the QRS complex in here. So how many boxes are in here? One, two, three. So this QRS complex, this one starts here. So it says 1 2 3 and a half. So it's greater than.12. So about 3 and 12 boxes. So the QRS complex is greater than.12. If a QRS complex is greater than 0.12 seconds, we know that it's taken the impulse too long to get through the ventricle and hence we have a block in our ventricle and we call it an intraventricular conduction delay. So the impulse starts in the SA node, comes down the the interodal pathways to the AV node, travels through the bundle, down the right and left bundle branch, gets to a block and has to take an alternate route like a detour or it goes through here, but it takes longer. Either way, you see it takes longer for that impulse. takes too long for that impulse to come up and around the ventricle. And we recognize that by measuring a QRS complex, which is an indication of the ventricle. And see this one here is 1 2 3 and 1/2 boxes. So definitely we have a QRS complex that's measuring too wide. So this person is in a sinus brady because we see that he does have a sinus rhythm. We can't dispute that it's a sinus rhythm. It starts with an the Pwave, the SA node. It's a sinus brady. And then we would just say with an IVCD or an intra ventricular conduction delay. And we know any time the QRS complex is going to measure greater than 0.12, we'll call it an intraventar conduction delay. Now is that a bundle branch block? Probably. But we don't know if it's the right or the left or if it's in the bundle of his. We don't know where it is. But when we get a 12 lead, we'll determine exactly where the the block is. Now, this is our second type of blocks we're going to talk about. We're talking about the AV heart blocks. And so, remember that occurs here's the SA node, interodal pathways, AV node. And this is where the AV blocks are occurring. So keep in mind a first a second and there's two different types of secondderee blocks and a third a node uh block first being the most mild three being the most severe. When we talk about firstderee AV blocks and keep in mind when we're talking about an AV block this impulse comes through here and it gets blocked somehow in this section and that's why it's called an AV heart block. First degree heart block. Every single impulse gets through the AV node. So the impulse starts comes here gets a little delayed and travels down. The next one starts in the SA node comes to the AV node gets a little delayed travels down. Every single beat gets through it's just delayed. Okay. So you can see that somebody can have a firstdegree block and really may not have any symptoms at all. There's just a delay. Super easy to diagnose a firstderee AV block. Then we take a look at all of our different steps. We take a look at the rate of regular. Is there a Pwave? Yes. So they all look the same. Is there a P for every QR? Yeah. Let's do a measurement of a PR. And this is kind of hard to to see right here, but we can see the PR right here. all the way to here and it's greater than 0.2 seconds. See how much how how long these PR intervals are. So they're greater than.20 seconds. Since they're greater than 0.20 seconds, we have a prolonged PR interval. That's considered a firstderee AV block. The rhythm is regular. It's um the PR interval is greater than 0.2. The Pwave is normal and the QRS is norm measuring normal as well. So the only abnormal here is the PR interval is greater than.20 seconds. And that's it. Every beat gets through the AV node. They just get a little held up in here because there's something that's causing this AV node to just not conduct through the way that it should. Now a second degree block not all of the impulses get through the AV node. Only some of the impulses get through the AV node. Whereas the first degree all of them got through they just got held up a little bit. So some get through and some die right in the AV node. So second degree AV block we have the impulse that starts up here travels down gets delayed and comes through and the next one starts comes out and may not even get through and just end right there. So let's take a look at this second degree AV block which we call Mobitz type two. We could have ratios and I'll kind of tell you what that means in a minute. So let's take a look at this right here. We have a pqrst pqrst p nothing. pqrst pqrst p nothing. Okay. So we take a look at the rate 1 2 3 4. Rate is 40. Rhythm is irregular. The PR interval is normal, but there's more Pwaves than QRS complexes. See these P waves that just stand alone right here. So when we look to see if there's a Pwave married to QR, each QRS, there's not. Okay, so that's a problem. When we see more P's than QRS's, there's some kind of block. The Pwave looks fine. There's no problem in the SA node or the atrium. The and the QRS tends to be a little bit on the wide side, but not necessarily. So, the main thing we need to see is some of the impulses get through. So, let's take a look at the first beat. The first beat right here. Okay, this first beat right here starts up in the SA node, travels down PQRS. No problem. Second one, SA node P QRS, no problem. Third beat comes from the SA node, goes into the AV node, dies. So we have atrial deolarization and it never gets through the ventricle. So there's a block there. It's next beat comes up here. PR interval gets through QRS PQRS. So some of them get blocked and some of them get through. So this looks like it's a ratio of two beats to one missed. Two beats to one blocked. So it's a 2:1 block. Two get through, one gets blocked. Two get through, one get blocked. So this is a secondderee AV block. Mobitz type two. Some of the beads get through. This up here is another secondderee block. Second degree AV block type one. or a Mobitz one and another name for it is a winky block. So keep in mind it's a second degree block so some are going to get through it just a little different pattern than Mobitz 2. So Mobitz one is winky block and some get through. So you can see here a Pwave QRST a Pwave QRST a Pwave QRST a Pwave then there's no QRS right here and then a Pwave again. So here's a Pwave that's standing alone. But let's take a look at it. Why is this called something different than this? Mobitz one has a prolonged PR interval. the rhythm increasingly prolonged and it should be here. Increasingly prolonged PR interval and the PR interval is irregular. So look at this PR interval right here and then we take a look at the next PR interval and look how long much longer it is. If we measured it, it would measure longer. Then we look at the third one. Whoops. Sorry, I'm not even looking at I'm not even given the right spot. I'm sorry. PR. This PR is longer. This PR is even longer until the third one or excuse me the fourth one. There's no QRS. So let's show see what's happening in this one right here. We have the SA node, the AV node and the perkis. Okay. So let's take a look at this number. First beat impulse leaves the SA node goes to the P the um AV node. It gets through. The second one leaves the essay, goes to the AV node, gets stuck a little longer. PR interval gets longer, gets through. This third one comes from the SA node, goes to the AV node, gets stuck even longer, but makes it through. So, even a longer PR interval. And then the fourth one, nothing wrong with the SA node, nothing wrong with the atrium. the impulse comes through and gets stuck in the AV node and dies and we have a Pwave with no QRS complex and then the cycle starts up again. So the rhythm is always an irregular rhythm with a PR interval that increasingly lengthens and that's the second degree. The last type of ABB block which is the final which is third degree AB block is the most severe and basically what's happening here is we have the heart and we have the SA node sends an impulse to the AV node remember this is where the block is and this is a severe block so pretty much you can just cut this in half right here there's absolutely no communication between the atrium and ventricle a complete hard heart block third degree is a complete heart block. So none of the impulses, we have all of them getting through, we have some of them getting through, some of them getting through, none of them get through. They all die in the A node. So basically we have Pwave, Pwave, Pwave, Pwave, Pwave, Pwave, Pwave, Pwave. The SA node doesn't know there's a problem. So it initiates an impulse, travels down, dies. initiates an impulse, travels down, dies, initiates an impulse, keeps doing that, keeps doing that. So there's P waves that march out completely regular. Well, what happens in our heart? If the SA node doesn't work, the AV node takes over. If the AV node doesn't work, the ventricle takes over. The ventricle only has the ability to beat about 40 times a minute. So the ventricle recognizes that there's no impulse coming from up the AV node. So the ventricle says, "Well, let me take over." Okay, there's nothing wrong with me. I still work. It's this AV junction that's not working. So it initiates a beat. So we have a QRS comics generally around a rate of 40 here. Ventricle beat, ventricle beat. So you would march out all the QRS's, the R to R to R to R to R to R, all regular because the ventricle is working great on its own. And then the atrium has no idea what's going on. P's march out to P. And sometimes they get a little hidden. There's probably one hidden under here. You can see that T-wave here, here, here, here. But there's no relationship between the atrium and ventricle at all. So there's no consistency with the PR intervals. They're just all completely different. The rhythm does look regular because there's nothing wrong with the ventricle. And so it tends to look ra regular, but it's always slow because the ventricle can't beat faster than 40 times a minute. There is no PR interval. There's no connection be for them at all. There is a Pwave. We just talked about that, but it doesn't relate to the QRS at all. And because the beat comes out of the ventricle, the QRS typically is wide. It's typically greater than.12 seconds because it's initiating from here somewhere and it just takes a funky pattern to get around. So those are the different heart blocks. Okay.