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Hello everybody. This is Ken Grauer. Welcome to the session. This is my fourth session on this first series. I'm doing cardiac arrhythmias 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. Hopefully present an approach that makes ecg interpretation easier for you more accurate, more time efficient. All I wanna mention from review of the past two sessions is my system for arrhythmia interpretation. And I still find after decades of looking at cardiac rhythms that unless I'm systematic, I miss things, 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. 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 for the A V blocks that I'm covering today. I like the kiss method. The kiss method basically keep it simple. There are three degrees of A V block, there's the first degree and that's easy to diagnose because all you do is see that there's a sinus rhythm with a long pr interval for the third degree. That's also easy. And this is what most people don't realize the reason third degree or complete a V block. Those are synonyms. The reason that's easy to diagnose is that most of the time, not 100% but most of the time the escape rhythm wherever it comes from the junction or the ventricles will be regular. So kiss method for the three degrees of A V block, if I have an A V block and it's not first degree and it's not third degree. What degree is it? It's second degree. And as we talked about last time, there are three types of second degree AV block, there is Mobitz type one, Mobitz type two and then sometimes you have 2 to 1 conduction, which means it could be either Mobitz one or Mobitz two. This is the case. It's EC GB block number 191. This two lead rhythm strip was obtained from an older woman who presented to the emergency department after syncope is the rhythm, complete a V block. Watch your P's and Q's and the three Rs. So looking for P waves or atrial activity is the CRS wide or is it narrow? And the three Rs being the rate of the rhythm, the regularity. And if there are P waves, are they related to the CRS complex, isn't it much easier to look at this? Once I've labeled the P waves, why did I use this pink arrow? And the answer is because it's hidden within the QR S, am I 1000% sure that there's ap wave in here. No. Why? Because the QR S is covering it. But this is an important concept. So with difficult rhythms and this is a challenging rhythm, I always divide the rhythm into easier parts and more difficult parts. And I like to start with the easier parts. The easier parts are, let's see if there's an underlying rhythm. The easier parts deal with. Watch your P's Qs three Rs is the ventricular rhythm regular. What do you think to the P SQ three Rs? We have answered the question that yes, there are P waves that are pretty regular and the QR S is regular and the QR S is wide. And what is the rate? The ventricular rhythm is 123456, a little bit more than six large boxes, 300 by six. So the rate is 50 a little bit less than 50 per minute. What is the last component of the PQ? Three Rs? We didn't do the last R which is related RP waves that we see are they related to the QR S complex? How do you tell and the way that you tell the easiest way for me, I look in front of each QR S and I look for AP wave and tell me if the pr interval is the same here, it's longer and here it's longer here. This is really short and here there's AP wave, it's right on top of the QR S. So how many think there is no relation of P waves to the QR s? Now, how do we define complete a V block? The easiest way to tell if the P wave might be related to the QR S is whether you have any repetitive Pr intervals. Do you have pr intervals that are seen that are identical pr intervals that occur more than once? And we don't P waves, they are marching through at a regular rate through the QR S complex with no relation. So third degree A V block, regular atrial rhythm or fairly regular atrial rhythm, if there's underlying sinus arrhythmia, regular ventricular rhythm and there's no relation to them. There is one last part of the definition of complete A V block that in my experience, most providers even experienced ones forget in order to call something complete A V block, you need to have P waves occur at all phases of the cycle, the RR interval that have a chance to conduct but still fail to do. So what do I mean by this? Well, if you look at all of these P waves, most of them occur either in the middle of the RR interval or close to the QR S complex. But I don't have a lot of P waves occurring there, there, there, this P wave right in front of beat number four, there's no way that can conduct, it's way too short to conduct. So let me prove this with the last part of this tracing here are the last couple of beats and I'm going to give you a couple of moments to look at this rhythm strip, look in particular at the last couple of beats. Now, what happens both to the QR S complex and the question of a relation between P waves and the QR S for the last part of this tracing? How many think this is still complete AV block? How many think this is now definitely not complete AV block? Tell me about the P waves, don't they continue regular or almost regular throughout the entire tracing? What has happened to the QR S complex? What has happened to the CRS complex? Now, look in front of each QR S complex for these last four beats. What do you see? Do you see P waves is the PR interval constant are these last four beats conducting? You should be able to appreciate that the Pr interval is constant which tells you what these last four beats are conducting. But is every P wave conducting? How many P waves are conducting? We see this better at the latter gram beat. Number seven has a constant pr interval, the same pr interval as all of these beats. So it's conducting all of the P waves in today's tracing go through the atria because we see the P wave they get through the atria. So you see a pretty regular pretty vertical line through the atrial tear. That's because conduction is pretty fast through the atrium beat. Number seven is sinus conducted. Once you get from the SA node to the AV node conduction slows down. That's why there's a little angle here. This is the amount of time it takes to write the pr interval. And then once you get into the ventricular conduction system because it's a narrow QR S conduction is fast. Again, this is the conducted beat. What happens to this P wave it gets blocked, it doesn't get through the A V node every other P wave starting with beat number six conducts. So we have what's known as a 2 to 1 A V block. What degree is it? Is it first degree? No, because I don't have every P wave conducting. Is it third degree? No, because we have some P waves that are conducting. Therefore, by kiss the kiss method, this is a type of second degree block and this is the special type of second degree A V block because there is 2 to 1 conduction. What happens with Wky Bak is the pr interval progressively increases until you drop a beat. The problem is if I only conduct one beat and then I drop it one beat and then I conduct is I never know if I'm conducting P waves don't have a chance to increase the pr interval. Which is why when you have a 2 to 1 block, we cannot be sure which type we have, but we do have a second degree A V block. Now, what is the LA gram showing in this part? Where are the impulses beginning? Well, they're beginning from the ventricles. These are ventricular beats, they conduct backwards and they prevent conduction of these impulses down to the ventricles. I need to get to the difference between V dissociation and complete AV block. AV dissociation is not the same as complete AV block. There are three types of a dissociation. This is a schematic illustration of what we have a regular ventricular rhythm. We have regular P waves. The rate is slow ventricular rate is a little over 30. Do these P waves conduct? So we look in front of each pr interval continuously changes this complete a V block. Do these P waves have a chance to conduct? Yes, because they pretty much occur everywhere and they fail to conduct. Now, where is the escape focus? But the cures is wide. So it comes from the ventricles as opposed to this example of complete AV block, none of these P waves have a chance to conduct but the QR S is narrow. So where is the escape? It's probably at the V node. Look at this rhythm. Is there AV block? If so what degree of AV block is present? Is my patient stable? I'm gonna say yes, the patient's stable, the patient's not stable. You might have to do something before you figure out the rhythm. Since the patient's stable. Watch my PS and Qs in three Rs. What can we say, regularity of the ventricular rhythm even without calipers. What do you think pretty regular is the C wide or narrow, pretty narrow, isn't it? Are there P waves, red arrows is the hint. Yes, there are P waves and yes, the atrial rhythm looks pretty regular but are these P waves the third R are these P waves conducting? Now, if I just looked at this P wave in front of beat number one, I would not know if this P wave is conducting or not. It's a reasonable pr interval probably a little bit less than 0.2. So I would not know. But what about this P wave? And this P wave there is no way that these P waves are conducting. So this defines AV dissociation is this complete AV block? Whether any of the P waves on this tracing have a reasonable chance to conduct and still fail to do so and none of them do because the pr interval is short, I don't have any P waves occurring here or here we're here. This is a V dissociation and I have no idea if there is any degree of a V block, there are three types of a V dissociation. There's what's known as a V dissociation by default by usurpation and by a V block. What do I mean by that? There is default because the sinus pacemaker, the sa node slows down. The A V node may take over. This was a healthy individual who basically was put under anesthesia which often slows the rate and look at the rate of the A V node. It's about 55. The sinus rate is about 50. So this is default. What happened was there was sinus bradycardia. So a normal A V nodal escape pacemaker took over. This is a V dissociation by default. And if you only showed me this rhythm without telling me the history, I would say I have no idea if there's heart block, but there is no evidence of any A V block. Now, the second type of A V dissociation is usurpation. What do I mean by that? I mean that one of the other escaped pacemakers, either the A V node or the ventricles accelerates to faster than the sinus rate. Since the CRS is narrow here, this is the A V node. And I will say it's pretty uncommon to see an accelerated junctional rhythm. You may see it with acute infarction after surgery, open heart surgery, shocky patients. But it's not that common. But what happened here is none of these P waves really have a chance to conduct because the AV node took over. So this is av dissociation by usurpation and I have no idea if there's any degree of heart block at all. What's the difference with this last example, regular P wave rhythm, right, red arrows, regular QR s coming from the ventricles cause it's wide, no relation between P waves and QR S complexes. Now, ideally, I would like to see a little longer tracing here. Basically, it looks like none of these beats are conducting. This is complete a V block at the ventricular level. So I'm gonna finish with one last look at the later gram of today's case, none of these P waves in the first five beats conducted, they didn't have adequate chance to. But because there's a little sinus arrhythmia, eventually one of these P waves occurs at a point when it is able to conduct. So what do we have? We have second degree AV block 2 to 1 AV conduction. And we also have some a V dissociation that occurs. Now, when there is conduction, the rate it's slow, it's about 50 but it's not that slow. It is likely to be Mobitz one or Mobitz two, which one's more common in my experience, Mobitz one or A B. Winkie B is about 95% if not more common than Mobitz two. Mobitz two is rare with Mobitz two. The C is usually wide here. It's narrow. You want to recognize Mobitz two is because those patients need a pacemaker. It's much less stable this particular rhythm. I would look at this and I would say, well, there's avid association but the patient can conduct. It's a second degree block, it's probably Mobitz one and at a rate of 50 the patient may or may not be stable. I need clinical correlation for that.