before we get started you have to understand which leads on the ecg correspond to which portion that's reading the heart and what i mean by this is we group our leads into four different categories so leads 2 3 avf leaves 1 avl v5 and v6 leads v1 and v2 and leads v3 and v4 these correspond respectively to inferior leads lateral leads anterior leads and septal leads now oftentimes v1 v2 v3 and v4 are all grouped into one category of four leads which we call anterior septal and this is what that looks like and the reason that this is important is because when you see different changes in these leads you have to know which leads we're talking about so if you see changes in 2 3 or avf the pathology is inferiorly located so those are the inferior leads shown here in green lateral is b5 v6 1 and avl shown in blue v1 and v2 are anterior v3 and v4 are septal but they're oftentimes grouped into one big category where the four leads together are referred to as anterior septal so they just can literally combine the words so i want you to memorize that first so pause the video and really get that down if you don't have it down already but assuming that you do and you're comfortable with the way that these leads work let's move on and talk about my mnemonic for remembering these leads because again if you're not there yet you have to have a way to memorize this because this is very important when you're taking your board exam so i'm going to push that information to the left and draw my stick figure here and when i was a medical student it didn't really make a lot of sense to me that where the leads were in space corresponded to different parts of the heart now if you're going to be a cardiologist maybe you understand that geographic orientation but i didn't go into cardiology so i needed a different way to memorize this so how i did this was with a few pneumonics so the first one is two to three feet and feet are the most inferior portion of the body so two to three for leads two and lead three and feet for av f the f in feet for the f and avf and two to three feet are always at the inferior portion of the body so i remember that two to three feet are inferior i also remember that one hand with five to six fingers is lateral so one for lead one hand with five to six fingers for v5 and v6 and then the hand is the lateral most part of the body so that reminds me that these are lateral leads and lateral for the l in avl you can use my mnemonics you can do your fancy cardiology things that you try to do when you're a gunner and you impress people in medical school but either way as long as you know where the leads are i'm fine with that so this is a normal electrocardiogram and i think it's really worthwhile to stare at some normal ecgs before we talk about the abnormal ecgs because if you don't know what normal looks like how the hell are you going to know what abnormal looks like so really take this in some medical students really get scared when they see v1 v2 v3 and v4 because they see that the st segment might be elevated but um i was lucky enough to do a rotation with a really really great cardiologist when i was a medical student and basically what he told me is that from v1 to v4 those st segments are going to get a little bit bigger with each successive lead so don't be scared if it's if it's rising proportionally then it's normal if they're super off the page then obviously it's going to be abnormal and we'll get into all that as we go today but the reason that i bring that up is because a lot of medical students look at v1 v2 v3 v4 and they're like wait is this a stemi is this an st segment elevated myocardial infarction but it should go up from v1 to v4 so this is normal stare at it get comfy with it you're going to look at the ecg you're going to find if it's sinus or not and you're going to find out if there's any other abnormal findings like st segment elevation st segment depression q waves for different types of ischemia etc so i don't want you to come into this lecture being like rate rhythm axis the don't do that that's not going to help you on usmle and it's not going to help you on complex here is where you look for p waves now the best leads to find p waves according to the cardiologist that i worked with is lead 2 and lead v1 they're just the most evident in those leads and i've drawn in here with black arrows some p waves in lead 2 and lead v1 and they're kind of subtle but they're definitely there right you can clearly discern that there are p waves there and where this gets tricky is medical students will look at an electrocardiogram and be like oh i don't know is that a p wave is it buried in the qrs i don't know is that a p wave is that a little squiggly thing is that artifact everyone loves saying the word artifact is that artifact no it's a p wave look in lead two and lead v1 and find p waves if you find p waves it's a sinus rhythm so here's our first one the question is what are we looking at what kind of ecg is this okay so pause the video if you want to think about it but what you're seeing here is an st segment elevated mi in the inferior leads so what i'm showing you is the inferior leads leads 2 3 and avf see those red arrows they are pointing to st segment elevation and the reason that i put the blue arrow in is to show you that comparatively the st segment of lead v3 which would be not in the inferior leads is not elevated so this is a stemi localized to the inferior leads now if you look at this ecg i want you to theoretically ask yourself what would have happened if you went through this with a dumb methodical approach that they teach you in medical school well rate uh the the the rhythm what do i see axis uh well let's see one is upright and avf is upright so the axis is normal what does that get you where does that get you in this question it gets you absolutely nowhere or you could just look at this and say hmm two 3 avf of fst segment elevation let me compare the st segments to the other segments well none of the other ones are elevated so this is a stemi is this sinus not that it really matters in this question but we look at v1 and icp waves we look at 2 and icp waves so it's sinus so it's a sinus rhythm but there's an st segment elevated mi done answer it check the box move on that's that's what i'm saying here don't go through that methodical crap unless you're going into cardiology or you really want a mastery level understanding of ecgs if you just want to dominate boards do it this way so this is a stemi what do we see here pause the video if you need more time and in three seconds i'm going to tell you this is another stemi but this one is anterior septal right so look at the red arrows those are st segment elevations that corresponds to v2 v3 v4 v5 and v6 so v5 and v6 are lateral and v2 v3 and v4 are anterior septal so we combine them and we say this is an enteroceptal lateral stemi and then look at the blue arrow right look at avl not really elevated so we can localize this mostly to v2 through v6 which would be anterior lateral anteroceptor lateral or anterior lateral now on a test they could simply ask you what type of stemi is this and you would pick the answer that says anterolateral or anteroceptolateral or they could flip it on you and in the vignette describe the leads with the sd segment elevation or describe even the name they could say something like enteroceptilateral and then ask you which leads you would expect to find the st segment elevation and that goes back to my point it's very important to be able to correlate leads to location so those are stemis and stemis are the highest yield ecg's that you could probably see on usmle and comlex because they're pretty easy to get and to be fair guys on usmle and complex they have to give you very straightforward ecgs they can't make it too challenging if they did it would be way beyond your level as a medical student and everybody would get the question wrong and one of the themes of us emily and comlex is that the questions really can't be controversial so that is an enteroceptal lateral stemi let's move on to the next example what are you seeing here now this one's a little trickier it's a little more subtle but as soon as i point out the answer to you i don't think you'll ever get this wrong again so pause the video if you really want to look and dissect this ecg but in three seconds i'm going to give you the answer this is wolf parkinson white syndrome and what i've highlighted here with the red arrows is what's called a delta wave now a delta wave is a slight upslanting of the beginning of the qrs complex and this is classic of wolff parkinson white syndrome wolfe parkinson white syndrome has these delta waves the slight upslanting of the qrs and if you really put on your bifocals and zoom in here you can see that upslanding portion of the qrs now in real life this is a pretty rare disease but on us emily and complex it's pretty high yield because that subtle finding that upslanting of the qrs should tip you off that this is wpw syndrome and then from there they can go in a whole bunch of different directions by asking you things about pathophysiology about the treatment for wolf parkinson-white syndrome if you see the the answer procaine procainamide that's the answer but wolf parkinson white syndrome very very high yield be able to recognize this upslanting and again i'm just really gonna hone in on this you don't have to dissect this ecg and go rate what's the rate rhythm what's the rhythm axis what's the axis you see the delta wave the answer is wpw so what the hell is the point of doing that methodical dumb unnecessary waste of time method that you're seeing in all these other youtube videos okay guys look for the pathological findings and answer the damn question it's that simple wpw has the delta wave that up slants done moving on what do you see here this is a very very high yield ecg and it may not be obvious at first but i want you to pause the video and look around and see if you can tell me what we are looking at on this ecg this is atrial fibrillation and almost equally as high yield as stemi if not more so afib is very very high yield because it's so easy to recognize you don't see p waves and it's irregularly irregular right so in irregular intervals it's irregular so that's what irregularly irregular means and what you see there with the blue arrows is that the width between the qrs complexes is irregularly irregular right they're skipping different uh widths that is classic of afib and if you look up at the other leads you will not see discernible p waves you see a lot of squiggly crap but there's definitely no discernible p wave in lead 2 or lead v1 okay so this is afib very very high yield because they can get into pharmacology they can talk about rate control they can talk about rhythm control they can talk about hemodynamic changes and pathophysiology but you have to be able to recognize in a regularly irregular ecg with no p waves so again rate rhythm axis that doesn't get you anywhere the question is are there p waves and is this sinus in this case the answer is no and then you would look at this ecg after seeing that it's not sinus which eliminates a million things that it could possibly be and you'd see that a regularly irregular qrs interval and you'd say it's afib i'm done i got the point and i'm moving on that is atrial fibrillation this is our next example what is this pause the video if you need more time but i'm going to give you the answer this is atrial flutter and atrial flutter also has no p waves just like afib but the big difference between atrial flutter and atrial fibrillation is what's classically referred to as the sawtooth pattern and i've superimposed it on the slide for you to really be dramatic about what it looks like but on us emily or complex they have to give this to you they can't give you an a flutter question without the sawtooth appearance because you just frankly won't be able to answer the question so if you see that really choppy sawtooth pattern it's a flutter stop what you're doing pick it and move on so a flutter has no p waves and it's got the sawtooth pattern sort of like afib and that the rate is similar and maybe the appearance is similar in terms of no p waves so it's not sinus but look for the sawtooth appearance so that is atrial flutter so guys i want to pause for a second and highlight something here we are flying through this lecture but what i'm showing you is that you don't need to dissect ecgs like a cardiologist instead you should be dissecting ecg's like a medical student because hey after all you are one so look for p waves and after that just look at the ecg and get the pathologic finding because it's going to be obvious so we've done afib we've done a flutter we've done stemis and we've done wolf parkinson white syndrome with the upslanting delta wave let's move on and talk about some other really really high yield ecgs that don't get a lot of love in other review sources but i think you should know because if you could pick them out and correlate them to something in the vignette you're giving yourself free points so this one's really tricky and to be honest i don't expect you to get this until i teach you what it is and then from that point onward hopefully you'll never miss it again but pause the video if you want to look around on this ecg i'm going to give you the answer in three seconds so this is actually a pulmonary embolism and and what this is is called s1q3t3 now this is tricky and it's honestly beyond the level of a medical student but it still shows up on usmle and comlex because of how uh how high yield it is in terms of being able to correlate this with a pulmonary embolism so for whatever reason when somebody has a very large pe and this is more likely in something huge like a saddle embolus they get classic findings on the ecg and what those are are shown here on this slide so the s1 q3 t3 refers to a deep s wave in lead one so the s wave when it comes down will go deeper than it normally should so s1 s wave that goes very deep in lead one q3 means a deep q wave in lead three so normally the q wave kind of drops down a little bit but if it really goes deep that's q3 and then t3 stands for inverted t waves in lead three so a pulmonary embolism you really need to just look at leads one and lead three and if you see the deep s deep q and inverted t you should think pulmonary embolism now i want to be honest if you're on your exam this is probably going to be a choice of elimination and i remember when i was taking my exams if i had s1q3t3 but i couldn't recognize it by reading the electrocardiogram i would eliminate all of the other questions all of the other answers first and if i saw pulmonary embolism as a possible answer choice then that would cue my brain to look back at the ecg and be like oh maybe there's an s1 q3 t3 let me take a look and so you want to use the answers that they're giving you to look for the associated features so for example if you have a b c d and e as your possible answer choices and it's like afib a flutter wolf parkinson white inferior stemi and pulmonary embolism what should you look for so if the answer is a flutter look and see if there's a sawtooth pattern if the answer is a-fib look and see if it's irregularly irregular with no p waves if the answer is inferior stemi look for st segment elevation in leads 2 3 and avf if the answer is wolf parkinson white syndrome look at the qrs complexes and see is there an upslanting delta wave and if it's a pulmonary embolism look to see if there's s1q3t3 so that's the way that you should approach these you should look for the pathonemonic finding associated as a buzzword with your answers so that is a pulmonary embolism s1 q3 t3 let's move on to our next example what do you see here now i'll give you a little hint i'm not looking for an answer to like a disease here i'm looking for sort of a symptom pause the video if you need more time but in a few seconds i'm going to give you the answer so this is actually showing hypokalemia hypokalemia or low potassium and what you're seeing here is what's called a u wave now in i put something on top of the slide here to show you the difference between the ecg when it's normal kilemia which means your potassium is normal and the ecg when you have hypokalemia so now normally the t wave comes up and it's normal in size and then after it you see a small little bump which is a very very shallow u-wave if at all now sometimes that u-wave won't even be there but if it's there and it's normal it's going to be an ever slight little bump that's significantly smaller than the t-wave but in hypokalemia you get prominent u waves so instead of the u wave being very very small compared to the t wave or even absent it's much much larger than the t wave so what you see on the ecg that i've shown with the blue arrows is a prominent u wave that's come up and is bigger than the t wave and if you see that you should think of hypokalemia now the reason that this is high yield on usmle and comlex is because if they're going to show you an ecg with hypokalemia they're probably going to have you tie it in some way into a pathophysiology question or a pharmacology question asking you about hypokalemia so if you see this they're going to ask you an associated question which probably has to do with the cause of somebody having a low potassium so this ecg is often used to tie in high-yield associations which is why i've included it in this lecture it's extremely high yield so you see those uavs it's hypokalemia start to have your brain think of causes of hypokalemia because that's probably where the question is going here's our next example and obviously we just did hypokalemia so you can probably take a guess that this ecg is going to be something similar this is hyperkalemia so hyperkalemia shows what's called peaked t waves so the t waves kind of get really sharp and spiky and they come way up off the paper now i've superimposed something on this slide which shows you how the peak t waves appear in the different leads from v1 to v6 and the reason that this is important is because some medical students get mixed up between a peaked t wave and st segment elevation because they're seeing the t wave come up and they're not sure if that's s t segment or if that's just an isolated t wave that's peaked because of hyperkalemia so what i want to show you is that in these in these different leads if it's a peaked t wave it's kind of like somebody grabs the tip of the t wave and pulls it straight up but if it's an st segment elevation they have to grab the whole segment right from the s to the t so instead of it being a really spiky thing that you could like cut your finger on if you touch the tip of it uh that's what a peak t wave is st segment is more blunted right it's more rounded at the top because it's the whole entire segment and i really want to hone in on that because people will think that this is a stemi from leads say v2 to v4 but this is really just a peaked t wave now hyperkalemia can lead to a stemi but you have to be able to differentiate those two so in summary a peak t wave is very sharp at the top but st segment elevation is more blunted at the top more rounded at the top so be able to keep that straight in your head and just like hypokalemia hyperkalemia is going to be about some type of association and the question will no doubt ask you about pathophys or pharmacology leading to elevated potassium this is our next example this one little tricky at first but hopefully after i point this out to you you'll never get this question wrong because this is very high yield what do you see on this ecg pause the video if you need more time and in three seconds i'll give you the answer what you're seeing here is actually a prolonged qrs segment and what this what you'll see causing this is tricyclic antidepressant toxicity so if someone overdoses on any one of the tcas it prolongs their qrs and that can be really dangerous it's not something that you want to mess around with and if you've memorized your pharmacology already you know that tca toxicity leads to cardiotoxicity and this is how the prolonged qrs segment can lead you into dysrhythmia and cause death so you need to treat it very very fast and the treatment for tca toxicity is bicarb so bicarbonate will reverse the prolonged qrs but look at the blue arrows look at how long those qrs segments are actually lasting even if you had know nothing about ecg's but you've just been staring at normal ones you should be able to appreciate how long these qrs segments are so if you see a prolonged qrs on usmle or comlex they're telling you that someone overdosed or inadvertently took too many tcas you pick bicarb as the treatment prolonged qrs is the ecg answer be able to correlate all of that stuff because it's incredibly high yield here's our next example what do you see on this slide pause the video if you need more time and in a few seconds i'll give you the answer what you see here is pericarditis okay pericarditis classically causes diffuse st segment elevation in most leads and diffuse pr segment depression especially prominent in lead two so what i've shown you here is the blue arrows and the red arrows and what the blue arrows are showing you are pr segment depression so normally the pr segment should not be depressed under the line it should not go in the negative direction but look at the blue arrows the pr segment's moving downward so that is pr segment depression the red arrows are showing you diffuse st segment elevation now you might look at this at first and be like oh is this a stemi i see sd segment elevation and that could be possible but what you need to appreciate is that the st segment is diffusely elevated in all of the leads and of course it'd be very rare to have a stemi in every single lead at once you wouldn't be infarcting all of the vessels at your heart at once so this is probably pericarditis what will seal the deal for this question is the clinical vignette they will give you something extremely suggestive of pericarditis so they'll give you all of the other symptoms of pericarditis and then show you this ecg or vice versa and want you to tie these symptoms together so be aware that for pericarditis you will see st segment elevation but you'll see it in all leads you'll see a pr segment depression and if you see that on usmle or complex your brain should instantly think about pericarditis here's our next example what do you see on this slide now this one i will tell you is probably the trickiest of any of the ecgs that i've included in this video today but this one is really important to understand and we're going to spend a little bit of time on this because i think that understanding this is very very high yield pause the video if you need a few seconds but i'll give you the answer what you're seeing here is multifocal atrial tachycardia now i'm going to be honest when i was a medical student this was one of the ecgs that i got really nervous about because i didn't really understand what the word meant multifocal coming from different areas atrial means atrium right the atrium of the heart tachycardia means fast heart rate so this is a fast heart rate that is due to the atrium originating from multiple areas that is literally what multifocal atrial tachycardia means and what you see here is that there are three or more different p wave morphologies which all that means is that there are p waves and at least three of them look differently so let me explain this and i've superimposed a really clear-cut example with the black arrow showing you three different appearing p waves in lung disease now this is classically associated with lung disease so something like copd you have elevated pulmonary pressures which cause the atria of the heart to contract irregularly and all the atria technically have foci that can generate electricity and cause impulses through the heart now normally the sinoatrial node handles this but in lung disease the there are different areas of electric activity that are incorrectly generating electrical impulses so you see different p waves because there's the sinoatrial p wave but there's also the irregular p wave or the abnormal p wave if you will that's generating impulses due to lung disease causing pulmonary back up into the heart and when you see that on the ecg you'll see different looking p waves one is sinoatrial one's coming from the atrium closest to the pulmonary system and you have all of this mismatch and electrical activity which causes you to see different p waves on the electrocardiogram so if you see three or more different p waves it's multifocal atrial tachycardia and the reason that it's so high yield is a because the p waves will look different and it's a very subtle finding that they want you to be able to notice on an electrocardiogram but also because it's classically associated with lung disease so look in the vignette if they're giving you somebody who has copd or asthma or pulmonary hypertension or sarcoidosis or whatever it is it's probably going to be multifocal atrial tachycardia so remember mat is associated with pfts that was my pneumonic mat for multifocal atrial tachycardia is associated with pfts or pulmonary function testing somebody with abnormal pfts will have abnormal mats three or more different p waves because the heart is sending impulses from different areas because the lung disease is causing aberrant electrical activity of the atria