 Welcome to emergency medicine videos. This is part one of Erythmia. We will focus on bradycardic rhythms. We will first look at normal heart conduction, and then we will discuss bradycardic rhythms. First, normal heart conduction. There are three pacemakers in the heart. SA node, AV node and the ventricles. The SA node is the normal pacemaker of the heart. It beats at 60 to 100 beats per minute. Impulses originate from the SA node causing the atrium to depolarize. That is the P wave. It then travels to the AV node and down the hispagin G fibers. It then splits into the left and the right bundle branches, causing ventricular depolarization. That gives you the cure as complex. T waves represent repolarization of the ventricle. That is what happens if the sinus node is in charge of pacemaking. If the SA node falls below 60, then some of the other sites may take over. If the AV node takes over, it will beat at 40 to 60 beats per minute. If the ventricles take over, they will beat at 20 to 40 beats per minute. In both cases, since there are no atrial depolarization, there will be no P waves. In case of AV node taking over, that will create a junctional rhythm. The cure as complex is narrow. If the ventricles take over, the cure as complexes will be wide. These are important concepts when we try to tackle what kind of bradycardiac rhythms they are. Bradycardia is defined as a ventricular rate of less than 60 per minute. On a standard speed ECG rhythm strip, there will be more than five squares between the cure as complexes. Five squares on a standard rhythm strip also equals to one second. To assess a bradycardic rhythm, we look at the following. Whether there are P waves. If there are P wave, what is the PR interval? The relationship between P and QRS, whether there are P waves before each cure as complex and whether there is a cure as complexes after every P. We then look at the RR interval to see if it is regular or not and whether the cure as complexes are narrow or wide. Let's look at a few different rhythms. The first one is sinus bradycardia. In sinus bradycardia, the SA node is generating a slower than 60 beats per minute rhythm. Since it is coming from the SA node, there is a P wave. The PR interval is normal. A normal being less than five little squares. What about the relationship between P wave and cure as complexes? You can see that there is a P before each cure as and a cure as after every P. What about the RR interval? They look like they're regular and QRS is narrow. This next rhythm is a junctional rhythm. We kind of touched on that a little bit before. We know that junctional rhythm originates in the AV node. Because of that, there will be no P wave and hence you cannot look at a PR interval. Since there are no P wave, there are also no relationship between the P wave and the cure as complex. What about the RR interval? They look regular and for junctional rhythm, the rate should be between 45 to 60. What about the cure as complex? Is it narrow or wide? It is narrow. Let's look at this rhythm. This is atrial fibrillation with a slow ventricular response. Can you see P waves? You don't. However, you do see a bit of wavering at the baseline. In here, you can see it kind of goes up and down a little bit. That is caused from the depolarization of the atrial myocytes. So no P wave equals no PR interval and no relationship between P and cure as complex. What about the RR interval? You can tell that these RR intervals are not the same at each other and the cure as complex is here are narrow. Each cure as complex occur when the impulse from the atrium gets transmitted through the AV node intermittently. How about this rhythm? This is atrial flutter with a slow ventricular response rate. Are there P waves? Well, there are these waves, which kind of look like P waves. However, these are not exactly P waves. These are flutter waves that represent fluttering of the atrium. And these flutter waves tend to have a sawtooth pattern on the ECG and also the rate of the fluttering is at 300. Since there are flutter waves, we might want to look at whether there are any relationship between the flutter waves and the cure as complexes. So what's the relationship like? You can see here there are four flutter waves before there is a cure as complex and there are three flutter waves before there is a cure as complex. So this is what we call atrial flutter with a variable block, meaning that the AV node only led certain cure as complexes through and at a variable rate. Therefore, if you look at the RR interval, you clearly see the RR interval is different. Are the cures narrow or wide? Cures is narrow. This next rhythm goes a little bit lower and we're looking at a idioventricular escape rhythm. This rate is about 30 to 45 usually and is generated in the hiss bundle. Since it is not generated from the SA node nor are there any contraction of the atrium, there will be no P waves and as a result, no way to measure the PR interval. Nor can we draw any conclusion between the P and the cure as complexes. Are the RR interval regular or irregular? The RR interval is regular and the cures complexes are narrow. The next real rhythm would be about AV blocks. These happen because there is a blockage of the impulses somewhere in the AV node. There are three types of AV blocks, first, second and third degree. Second degree AV blocks are also further divided into type 1 and type 2. First degree AV block. In this rhythm strip, where would you be spotting the P waves? Can you see them? Sometimes certain leads are easier to see P waves than others and I think in this instance, lead 3 is quite helpful and probably lead AVR is quite helpful. You spot the P waves in these leads. So yes, this will be P waves and in these leads, this will be P waves. So once you've spotted the P wave, you want to look at the PR interval. So how long are the PR interval in this rhythm strip? As we discussed before, the PR interval should normally be less than 5 little squares or 0.2 seconds. However, in first degree AV block, the PR interval is more than that. In first degree AV block, PR interval is more than 0.2 seconds. And keep in mind that the PR interval is measured from the beginning of P until you've hit the R wave. If you go through that criteria that we look at bradycardic rhythms, then we need to look at the P-Curus-Complexus relationship. And you can see that there is a one-to-one relationship between the P and the Curus-Complexus. Are the R-R interval regular or irregular? It looks pretty regular and the Curus-Complexus are narrow. We now move on to second degree AV block. It is divided into Mopitz type 1 and 2. Mopitz type 1 is also known as Wenkeback. In Mopitz type 1 or Wenkeback, the block is in or above the AV node. Let's look at our criteria. Are the P waves? Yes, there are. What about the PR interval? If you look at the PR interval in here, you notice that the PR interval progressively get a bit longer and eventually there is a P with a drop Curus-Complex. And this is what defines a second degree Mopitz type 1 AV block. There is no one-to-one relationship between P and Curus-Complexus because there will be more P waves than Curus-Complexus. What about the R-R interval? The R-R interval, as you can see, is irregular. The Curus-Complexus are narrow. This is second degree Mopitz type 2 AV block. This block occurs with the function in or below the AV block. Let's see if there are P waves. You can see that there are. There are the P waves here, here, and here. What about the PR interval? Is it long or is it normal? On this strip, the PR interval is long. Although it doesn't have to be in all second degree Mopitz type 2, sometimes the PR interval is normal. Compared to the previous Mopitz type 1, you can see that the PR interval does not change. It does not become longer. What about the relationship between P and Curus-Complexus? Once again, you can see that there is a drop Curus-Complexus right here. Therefore, you don't have a one-to-one relationship between P and the Curus-Complex. The R-R interval is irregular. What about the Curus-Complex? In this strip, the Curus-Complexus are wide. In other second degree Mopitz type 2 block, the Curus-Complex can be narrow. It really depends on whether the block is at or below the AV node. The lower the block is, the Curus-Complexus will be wide. The last AV block is third degree AV block or complete heart block. The dysfunction occurs below the AV node. This happens when the atria and the ventricles are controlled by different pacemakers and are functioning independently. Let's apply our rules. Are there P waves? Yes, you can see them quite easily here. What about P-R interval? If you look at the P wave, it's really hard to make out what the P-R interval is. Because there is no relationship between the P and the Curus-Complexus, the P-R interval is all over the map. What about the relationship between P and Curus-Complex? If you count out the number of P waves versus Curus-Complex, so let's look at all the P's first. So these are the ones that you can see fairly easily. And then there are some you may not see at first glance, such as this guy right here. That looks like a P wave, but it's kind of buried in that ST segment. And also if you go back here, this is probably another P wave that's buried in that T wave. This is another P wave. So you can see there are definitely more P waves than there are Curus-Complexus. What about the R-R interval? The R-R interval in complete hard block is regular. This is because the ventricles has found its own pacemaker and it is adhering to that rate by itself. What about the Curus-Complex? Again, it depends on where the block is. If the block is closer to the His bundle, the Curus-Complex will be narrow. If it's distilled to the His bundle, the Curus-Complex will be wide. Let's say you're presented with this 12-litre ECG. Can you go through their criteria? First, are there P waves? You can pick them up fairly easily in lead 2. What about the P-R interval? It looks like the P-R interval is all over the map. Is there a relationship between P and Curus-Complexus? It looks like there are way more P waves than there are Curus-Complexus. So the next question is, are the R-R interval regular or irregular? The R-R interval at this ECG is regular and the Curus-Complexus are narrow. Based on the criteria that we looked at, this is another example of a complete hard block. Let's review what we've learned. You want to assess the Bratic-Cardic rhythm by seeing whether there are P waves. If there are, measure the P-R interval, then look at the relationship between P and Curus-Complex. Measure the R-R interval, and then seeing whether the Curus is narrow or wide. We hope you find this helpful. Thank you for watching.