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And urine and I'll be presenting C GS today. So, if you don't know me already, I've taught cardio and ophthalmology. Um and this is gonna be my third teaching session with EC C GS. Now, I have to admit I haven't done this for about maybe, let's say three years. So I'm slightly nervous as to how this will go. But um let's, let's see how we do and yeah, hopefully this should give you a good basis. Um When am I on, on me? OK. Um This will give you a good basis on how to interpret EC GS um and also how to summarize them and to present them to your examiner. So, what we'll be talking about today is the basics, how to interpret a single trace, the pathologies that you could detect. I won't be talking about all of them, but I'll be talking about some of the high yield ones and also just putting it all together. Um Just so you understand it and how to present it back to your examiner. So, in terms of basics, first of all, we need to know what is an E CG um the electrodes, the domains of an ECG. So, what are we looking at? And what aspect of the heart is being, um, assessed on each lead also, setting it up. Uh, we'll go, we'll, as we, as we go along, we'll talk about how to set one up. Um, and this, this presentation shouldn't last more than an hour and a half. Um, because it's just hard to interpret an ECG. Um, and I won't be, II won't be delving too much into management. Um But yeah, so in terms of an E CG, simply put is a machine that uh measures electrical activity on your skin. Um and interprets it, uh interprets it as the uh heart's electrical activity. So it's used to give certain angles on the heart um based on the electrodes. So you've got negative and positive leads, uh electrodes, sorry. Um And you typically look down from the positive side, but we'll go into that, um, later on. So you use this in parallel with other clinical investigations essentially to diagnose patients. So typically we wanna use things like um troponins as well. When we talk about acute coronary syndrome, there's a sample trace. So for the more senior ones among us, I think, um this is pretty straightforward, um kind of know what's what, but for the more junior ones among us, uh especially those starting out in their ay, um this might be quite overwhelming being a lot of things like 12 A VL, you know, V two V five. What, what's all this? So hopefully we'll unpick all of this and uh make sure everybody understands it on the same level. So talking about the electrodes, so we use a 12 lead system. So three of them are the bipolar leads. So that's the three big leads that you typically know of an N A CG. So it does lead 12 and three. And then we got three augmented unipolar leads. So these are based off the bipolar leads and they also give you another kind of view into the heart. Um It's just, you know, another, another view. So why not? And the six chest leads, basically, they give you a cross sectional view of the heart uh especially in the anterior area. Um But we'll go into that later on and what it means to be unipolar. So in terms of the bipolar limb leads, uh a lot of us will be familiar with riding your green bike. So going from your right arm to your left arm to your left leg, to your right leg. So almost like a box um like soap. Uh this is a drawing of my own. So they might not be great drawings, but you know, they're uh they serve me well. So in terms of riding a green bike, so you would typically have a bunch of leads that you separate and the most outer ones, they will be either red, yellow or green and black. So you put um the red one on your right arm, the yellow one on your left arm, the green one on your left foot and the black one on the right foot. So in terms of what's positive, what's negative, I think it's worth memorizing and drawing this down. But uh in terms of lead one, negative to positive goes from right to arm to left arm. For lead two, it goes from right to arm to left foot. Like so and lead three goes from left arm to your right foot. So I've drawn it here for convenience. But uh if you guys wanna try and remember it, I think it's best to keep drawing it out. And conveniently what I've put is are these arrows and these eyes basically to show what they look at. So if you think about almost like an arrow in the eye, um they give you that perspective of the heart side. So you're able to, for example, um let's say an ECG trace flags an anomaly on lead two and three, your eyes would almost be down here. So you're essentially looking at the inferior aspect of the heart. And likewise, er for lead one, you'll be looking more at the er left side. Oh, the lateral side should I say sorry? So in terms of the augmented unipolar leads, um these leads, as I said, offer another perspective on the heart. Um and it essentially go from like the base of the triangle up to the limb in question. So VR being like right arm, a VL being left arm and VF being uh foot, a like a V foot basically. So as I, as I mentioned earlier, so it goes from the base to the limb in question. So that's sort of the, the, the view that you get and it, it applies similarly in the sense that the arrow um is sort of the angle you're looking at. So especially when the art, it's a common exam question to ask you what, you know, um what arteries affected. Um And this is kind of a way that if you're stuck on what's going on, this is something you can think about. So in terms of chess leads, we'll talk about setting up chess leads here as well. Um They seem rather confusing cos you know, there's about like six of them there. But um when you think about how systematic it is, I think you begin to develop a system for it. So starting off with V one, you wanna start in the fourth intercostal space on the right side. Um That's sort of your, your starting point really. And then from there, um the V two goes on the same si uh on the same like landmark just on the other side of the body. So your left side moving fourth, you go to V four. So V four just remember that is on the fifth intercultural space now. So moving down, but it's mid clavicular and V six is the other one to know. So that one is mid auxiliary on the fifth intercostal space. Now, V three and V five are the ones that go in between um their respective uh electrodes. So just moving back. So V three would go in between V two and V four and uh V five would go in between V four and V six. Sorry, that's a lot of words there. So as I said, they're unipolar leads, so they give you the cross sectional image. So these electrodes are only positive. So um all the electrical charges negative will move towards the er positive electrodes essential. So in terms of domains of an ECG, we'll, we'll practice this as we go along later. But um you could think of it as like um like a table, for example, if you, if you like learning of tables. So you know what's uh what needs see different size of the heart or you can also learn it quite visually as well. So I've drawn a few of my lovely diagrams again to try and show you but um if you think about the way the electrodes are orientated, um they kind of give you um a look as to what side of the heart is affected, for example, with lead one. the the bit shaded in pink is kind of what it looks at now, obviously, these are rough areas. But um I think as you do more questions and throughout time, they will sort of um embed themselves really. And um in terms of the chest leads. So V one and V one to V six kind of look at the cross sections. And um there are no negative electrodes here essentially. So the um positive impulse will be running along the chest leads um in the pos to form a positive reflection. So V one is actually a really good example um because the net vector is kind of moving to the left cos there's more sort of a there's a greater mass on the left ventricle. So it will sort of flag as a negative deflection in this case, um as all the charges are running away from it, uh the the uh depolarizing in charge, sorry, and just a disclaimer, sorry, there's not many SBA S in this ques in this uh session. So I have a few uh sample stations that we can all get involved in later on. So that's sort of my uh my equivalent of SBA S in this session I picked up on this uh this, this diagram actually recently. Um And it is quite helpful because it shows you um exactly kind of what arteries might be affected. So this is a really visual way of looking at it. Um So this is something you can consider looking at um especially in conjunction when you sort of answer questions and maybe eventually it will get to get to memorizing it. I think I might have jumped. Sorry. There we are. So interpreting a single trace. So first of all, I wanna talk about heart rate. So heart rate is something we need to look at and it's something that a lot of people, it's like kind of like fire and forget. Um But hopefully we will try and remember it. Now, we want to look at the, essentially the whole um story of the heart essentially. So the PQ RST um complexes. So the wiggling line essentially is just a the story of the heart in one sort of cycle essentially. And if you know your alphabets, you know that the E CG, so it's PQ RST, it's kind of straightforward there. Now, the rule of thumb that you remember is that the, the depolarization charge is negative. So when it moves towards a positive electrode, it records it as a positive deflection. Um But it's important to note that when there's repolarization um that energy is essentially positive. So when you move towards a negative electrode, it will record as a positive deflection. Um And that's really important when we talk about the T wave. So in terms of heart rate and rhythm, the standard rhythm trace that we use is 25 millimeters um per second. So that's something you need to check when you set up an ECG or when you interpret one to make sure it's 25 millimeters per second. So, a good way of remembering is one small square is equivalent to 0.04 seconds. Five small squares um is equivalent to 0.2 seconds. And also five small squares make up one large square.