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Hello everybody. This is Ken Grauer. This is my third session on E CG interpretation with a focus specially for these first four sessions on arrhythmia interpretation. My goal in the 30 minutes that I have available is to make this as user-friendly as possible to hopefully present an approach that makes ECG interpretation easier for you more accurate, more time efficient. Today, we're using blog 344. All you do is substitute the blog number to have a user-friendly link to get you right there. All I wanna mention from review of the past two sessions is my system for arrhythmia interpretation. Watch your P's and Q's and the three Rs remind you of the five parameters you want to use for any arrhythmia, fast rhythms, slow rhythms. S so looking for P waves or atrial activity is the QR S wide or is it narrow? And the three Rs being the rate of the rhythm, this is both the atrial and ventricular rhythm, the regularity and if there are P waves are they related to the QR S complex does not, does not matter in what sequence you ask yourself these questions as long as you always assess all five of these parameters. Here is the rhythm. How would you interpret this rhythm? Choices are sinus rhythm with blocked PA CS. Is there av dissociation? Complete AV block, second degree AV block Mobitz type one, second degree block. Mobitz type two. How many think it's complete AV block? Watch your P's and Q's and I use, watch your P's and Q's in the three Rs. This is my system for any rhythm. Now, I can do this in real time. This doesn't slow you down. On the contrary, it speeds me up. But the beauty of this system number one is you sound like you know what you're doing, you sound smart even if all you're doing is stalling until you can think of the particular answer. But it gives you the five things you need to think of, it prevents you from missing anything and sometimes no matter how good you are with rhythms, sometimes I don't know what the rhythm is. But if I can describe presence of atrial activity, QR s with and the three Rs, I've narrowed down my differential diagnosis. So let's think about those five parameters P wave. And I showed you this rhythm. Hopefully, you all saw that they're P waves. One of the easiest things to do that I find tremendously helpful is to label P waves. Isn't it a whole lot easier to see the P waves? Isn't it easier? Now to tell that these P waves are at least fairly regular. How many have heard of ventriculophasic sinus arrhythmia? And that's just a fancy word for saying a lot of times when you have a second degree or a third degree, a V block, the rhythm is not totally regular. There is a sinus arrhythmia. Think about the other piece, 23 hours. Again, it doesn't matter what sequence we ask ourselves. But I always go through these in my mind. The QR S is a wider narrow to realize what percentage of a 12 lead ECG do we have on this single lead rhythm strip? We only got 1/12. So it's possible on occasion that a part of the QR S may lie on the baseline at the one lead you're monitoring. So always, I like to get a 12 lead if your patient is stable. But looking at this, this really looks narrow. So until we know otherwise narrow QR S, how about the ventricular rhythm is the ventricular rhythm regular throughout and it's fairly regular for most of the rhythm except in the beginning, the rate. What is the ventricular rate? And let's for the moment, just forget about the first two beats. How many large boxes in the R tar interval? 12345, a little bit more than six boxes. The rate is a little bit under 50 BPM. P waves are they related to the CS complex? That's the third R and for the A V blocks. That is key. How do we know if P waves are at all related to the CS complex? And the way we know is you focus your eye on each of the Q RSS. Look in front of it. Look for AP wave, look at each QR s, look in front of it again, I'm gonna forget about these first two beats for the moment. Look at this pr interval is the pr interval constant pretty constant, isn't it? So P waves are related at least some of the time this P wave doesn't have any QR s near it. No neighboring QR s that's related to. But these P waves are related, these P waves are conducting. The A V blocks are not nearly as hard as many people make them out to be. There are only three degrees of a V block, first degree, second degree and third degree. That's it. Third degree is a synonym for complete A V block. First degree. A V block is easy to diagnose as I'm sure all of you that have experience with ecg interpretation. No, all we're talking about is a sinus rhythm with a long pr interval. So we said that beats number 3456 and seven. They're all conducting because there's a constant pr interval and it is clearly more than a large box in duration. So there is a first degree A V block. Now, one of the things, a lot of people don't realize the first time they hear it is you can have first degree A V block and second degree A V block, they're not exclusive. So we have at the least a first degree a V block, third degree A V block, none of the P waves conduct. So we have the P waves doing their own thing. We have the ventricular rhythm doing its own thing. And basically, there's none of the P waves that get through. This is surprisingly easy to diagnose. And a lot of people don't realize this. The reason third degree AV block is surprisingly easy to diagnose is because most of the time when you have an escape rhythm, the escape rhythm will be regular or at least fairly regular. If you look at a rhythm and the rhythm is not totally regular and there's an obviously regular part, it's probably not third degree AV block. Look at this rhythm. Look now at all seven beats. What did we say about the first couple of beats is the QR S complex regular. No. So even before I look at P waves and the neighboring QR S complexes, just looking at the rhythm tells me that this is not gonna be a third degree AV block. One of the best clues that you got a beat that's conducting is you see a beat that occurs earlier than you expect. This beat occurs early, it's probably conducting. So we have P waves that are present a narrow QRS complex P waves that are related P waves that are dropped in an earlier than expected beat. What kind of AV block is this? Is it first degree? Well, yes, it's first degree but it's not only first degree because there also dropped beats. Is it third degree? No, because these P waves are related fixed pr interval and this beat occurs early. So we have second degree, makes it easy if it's not first degree and not third degree, but it's ad block. It's a type of second degree now, which type and a lot of people just think that there are two types, but there are three types of second degree A V block. There is Mobitz one, there is Mobitz two and there is second degree AV block with 2 to 1 A V conduction couple points. Number one, Mobitz one is a synonym for A V wine bach. The pr interval gets progressively longer until you drop a beat. And then the cycle begins again as opposed to Mobitz two where the pr interval is constant until you drop one or more beats. Now, the important clinical points with this Mobitz one in my experience, 95% or more of all of the A V blocks I have ever in my life seen are gonna be Mobitz one. Mobitz two is uncommon if not rare. But when you see it, it's much worse. It's usually at a lower level in the conduction system which is why unlike Mobitz, one where the QR S tends to be narrow, the QR S tends to be wide with Mobitz two and you usually need a pacemaker. Now, what about this third type? Ok. This type, we have 2 to 1 conduction. Now, if we block out these first two beats, what do we have for? Beats 34567 conducts block conducts blocked conducts block. So we have a second degree A V block for beats number three through seven with 2 to 1 A V conduction or 2 to 1 A V block here. Do we ever see two conducted beats in a row that are progressively increasing? No. So the point of this third category is if you have a strict 2 to 1 block that you cannot tell with certainty whether or not you have Mobitz one or Mobitz two. And that's why there's a third category now clinically, why is this important? Well, it's important because most of the time the prognosis is much, much, much better with Mobitz one, which is by far the most common form because you usually have a narrow QR s which means that the block is at a higher level in the AV node, it's more likely to be associated with an inferior rather than an anterior infarction. And much of the time with acute uh infarction, it's transient. Whereas Mobitz two, the problem is you go from dropping one beat to all of a sudden ventricular standstill without any notice, which is why if ever you see Mobitz two, you need a pacemaker, which is why if we have 2 to 1 block, we wanna find out which one it is, it is unlikely for a patient to go in and out of Mobitz one. Then to Mobitz two, then to Mobitz one, it's usually one or the other. So you may have a period of 2 to 1 AV block for five minutes, let's say. And then the patient has typical Mobitz one elsewhere on the tracing. So it's probably all Mobitz one looking at this particular tracing before we focus on these first two beats. It's 2 to 1 block. But which one is it more likely Mobitz one? Why? Statistics? Because it's almost always Mobitz one and the QR S is narrow in my last couple of minutes. I'm gonna talk about a later gram. It took me literally a decade if not two decades to be comfortable drawing Lado grams. But to understand Lado grams, you're gonna be able to in the next five minutes and Lado grams are great because they explain the mechanism of the rhythm. They just make it a lot easier to see what's going on for any Lado gram. We have three tiers now rarely, there's 1/4 tier if you have SA block. But SA block is rare for practical purposes, there's travel through the Atria, through the A V node and through the ventricles along the horizontal axis is time. Now travel, here's ap wave travel through the atria fast. It's almost a straight line travel slows down a little bit as we go through the AV node. That's why this is angled. And then if you do not have a bundle branch block travel through the ventricle, the conduction systems pretty fast. But here in white, this P wave is blocked, doesn't get through the AV node. The next one conducts, the next one is blocked. The next one conducts and it's blocked. And then what happens with these first couple of beats? Well, here we have AP wave and this one conducts and then here, what do we have? This pr interval is a little bit longer and then the beat has dropped. What is this? If we only look at this cycle, we have a narrow pr s we have apr interval that gets longer, the beat has dropped. And then with the next cycle, the pr interval becomes shorter again. So this is clear Mobitz one, which tells us what about this whole rhythm? It tells us it's probably all Mobitz one because it's gonna be highly unlikely to go back and forth from Mobitz one to Mobitz two. And the C is, is narrow.