what's up ninja nerds in this video we're going to talk about how to systematically approach a 12-lead ekg and have a master interpretation of it before we start that though let's start talking about the basics of ekg the foundational concepts that you need to have in order to effectively and efficiently read 1280 kgs so what do i need you guys to know first the first thing is when you look at an ekg they have all these different deflections and blips up and blips down and flat lines what do all these things mean we should have a basic idea of that straightforward the first positive deflection or blip here is called your p wave the p wave is indicative of atrial depolarization so you have a structure here called the sa node in the upper part of the atria what happens is it intrinsically depolarize generates action potentials that spread throughout the atria that electrical activity that's spreading throughout the atrium from the sa node is represented by the p wave the next part is at the end of the p wave until you get to the qrs complex there's this flat line that's called the pr segment the pr segment is the time period where all those electrical activity that was coming from the sa node throughout the atria all converge and come on to the av node so the av node gets hit with that depolarizing wave and holds on to the electrical activity but doesn't send the electrical activity down to the ventricles yet it just holds on to it that pr segment is indicative of av node depolarization now let's add on to that if you take the p wave which is indicative of atrial depolarization and you take the pr segment which is indicative of av node depolarization combine those two together you get the pr interval which is the time span from which the sa node fires depolarizes the atria depolarizes the av node and it's just getting ready to send those action potentials down to the ventricles got it next part you have this down portion here up portion down portion and then back to a flat line this thing right here where you have the down portion this is called the q of the qrs complex this one up here is the r of the qrs complex and this one is the s waver component of the qrs complex what is it indicative of ventricular depolarization so followed back the av node depolarized finally it said hey ventricles take the electrical activity sends the electrical activity down to the ventricles they depolarize and what do they generate the qrs complex so indicative of ventricular depolarization after the qrs complex you have this s wave right after the s wave it goes up and then goes into this flat line this here is called your st segment the st segment is indicative of still ventricular depolarization but there's no net direction there's no net movement or electrical activity in a particular net direction it's just the ventricles are depolarized they're holding on to that positive charge and they're just getting ready to repolarize okay there's no net movement of electrical activity no particular vector being directed it's just the ventricles are still depolarized waiting to be repolarized that is the st segment the next part here is this next positive blip the next positive blip is called the t wave the t wave is remember what would we end off with st segment right that was the ventricles are depolarized still but they're just getting ready to repolarize what do you think the t wave is indicative of ventricular repolarization so finally the ventricles go from positive to a negative charge and they create this upward deflection called the t wave the last part of this ekg that i want us to talk about is what's called the qt interval so the qt interval it starts right here right before you have that q wave right so just as we get ready to go at that downward deflection all the way until after the t wave that is the qt interval it's indicative of the time period where the ventricles are depolarized and repolarized very important later when we talk about prolonged qt intervals okay so i think that gives us a big idea about the different components of an ekg particularly the waveform and what that tells us about the electrical activity of the heart the next thing that you need to know is how do we pick up the electrical activity of the heart how do we register that on an ekg paper or an ekg graph we utilize things called electrodes and electrodes there's a bunch of different types and we use these different things called leads to determine the electrical activity of the heart in different planes let's talk about that so here we have some hearts and we're going to focus on a particular electrical activity in a very specific portion of the heart and what leads which are going to be based upon the electrodes where we put them what leads tell us about the electrical activity in that portion so for example the inferior part of the heart which tells us a little bit about the right ventricle a little bit about the left ventricle leads 2 3 and avf are going to tell us about that part of the heart very important when we start talking about things called stemies st segment elevation demise the next one is if we're talking about the lateral ventricle the lateral wall of the left ventricle okay this whole portion is the electrical activity in that part is told to us by what leads 1 avl v5 and v6 okay next is the right ventricle the right ventricle the electrical activity in that part of the heart is told to us by what leads v1 v2 and avr last but not least the anterior portion of the heart and the septal portion of the heart is told to us by what elect the electro activity in that part of the heart is told to us by what leads v1 to v4 to quickly recap what all of these things mean we have 12 leads where did that 12 leads come from we have three bipolar limb leads lead one lead two and lead three okay we have three augmented unipolar limb leads that's avf avl and avr and we have six precordial chest leads which are going to be v1 2 3 4 5 and 6. that's where we get the 12 particular leads that tell us about the electrical activity of the heart for our ekgs now that we have a basic idea about the electrical activity what that tells us about the heart the different electrodes and leads that tell us about where the electrical activity is occurring in the heart let's talk very very briefly about the basic things that we need to know about an ekg strip all right so the last part that we need to understand is when you look at a 12 lead ekg there's all these boxes right and there's a big box and there's a bunch of boxes inside of it what the heck is that for what you need to know is that you have a big box and then inside of that big box there's a tiny bunch of little boxes right one large box is about five millimeters in height and it's about five millimeters in width why is that important well you should know what the height is telling you and you should know what the width is telling you height is telling you about amplitude it's something about voltage how much electrical activity that these uh different parts of the atrium ventricles can generate and the width is telling us about time how long is it taking for this electrical activity to move through the different portions of the heart why is that important we'll talk about that later as we go through our systematic approach but what i want you to know is to have some numbers in your head not so much the height but just to for thoroughness sake five millimeters of the large box is equivalent to 0.5 millivolts what i really want you to know is five millimeter millimeters in width is indicative of 0.2 seconds of time that that electrical activity has taken to occur and the same thing if you take a big box there's five little boxes that are going this way and five little boxes are going up this way there's about a total of uh five raised to the second power 25 little boxes in one big box if we take one of those 25 little boxes and zoom in on it what do we need to know about that same thing that we need to know about the large box its height and its width height is one millimeter with one millimeter so one millimeter of height tells us that this is equivalent to 0.1 all right and more importantly is one millimeter in width is indicative of 0.04 seconds of time that has occurred within the electrical activity of the heart these are the basic things that we need to know to be able to effectively and efficiently read 1280kg systematically now let's go ahead and talk about the next part of our systematic approach which is the rate in rhythm all right ninja in this video we're going to talk about how to determine the rate and rhythm on a 12 lead ekg so before we start doing that let's take a look here at this makeshift 12-lead ekg here and really quickly recap what we talked about in the basics one two three those leads are what your bipolar limb leads tell us about the vertical plane avr avl avf are going to be your augmented uni polar limb leads they tell us about the electrical activity in the vertical plane v1 v2 v3 v4 v5 v6 are your precordial chest leads they tell us about the electrical activity in a horizontal plane right now this is kind of what a 12-lead ekg should look like right we have all the different leads that we talked about 12 total leads and then we have a rhythm strip which focuses on one of those leads and continues out for about 10 seconds in duration usually the most common one is lead 2. so this is what kind of a 12 led kg should look like now how do we go about determining the rate of this actual 12 lead kg and then the rhythm let's go through it first thing i really want us to know is let's be simple right keep it simple are we going too fast too slow or is it a normal rate well i got to know what a normal rate is normal rate is between 60 to 100 beats per minute so if i'm less than that that's bradycardia if i'm greater than 100 that's tachycardia how do i determine this though there's a couple ways one is usually on the printout of the 1280kg they can give you the rate and for the most part those are usually accurate rates other than if they have peak t waves sometimes that can track off the t wave in the qrs complex for the most part the machine is relatively good at giving you a rate but always make sure how do we do that there's two methods there's the box method and then there's r waves times six so let me tell you the r waves times six it's a really quick easy one for example if i take here my r waves i take my rhythm strip i only look at rhythm strips first and i take and i count how many r waves i have in that 10 second strip i'm gonna count one two three four five six seven eight nine that's nine total r waves i'm gonna multiply that by six nine times 6 is 54. so 54 beats per minute is about my rate if i'm using utilizing that r wave times 6 method okay so that's a little slow i would kind of consider that maybe bradycardic okay let's use the other method the box method now remember this isn't perfectly to scale okay if we was perfectly to scale it would be you know it would work out perfectly but all you're doing is you're measuring the distance between an r wave and an r wave on the number of boxes between for example there's only one box between the r and r that's 300 beats per minute if it's two boxes that's just 300 divided by two that's 150 beats per minute if there's three boxes it's 300 divided by three that's 100 beats per minute okay so you can do it two ways you can say how fast am i going based upon the box method how many boxes divide it you know it's 300 divided by the number of boxes or how many r waves do i have multiplied by six okay we've kind of used the r wave method here because we drew this out so we said 54 beats per minute is about our rate so we're kind of in the bradycardia range next thing we do what's the rhythm is it regular or is it irregular how the heck do i determine that we look at our r to r interval so what i would do is is i would take like a little like note card and i would take the note card and i would make like a little line here and a little line there on my note card and then what i would do is i would track the actual line to line and make sure that it's pretty much constant as i go the entire length of the rhythm strip so that rdr interval that i mark on my note card has to be the same if it's not the same it is what irregular if it is happening every single time i line that up on my note card it is very very consistent constant r to r it's regular okay in this case here it's not going to be perfect but we're going to say it's regular okay so so far we know that we're bradycardic and we're going to say here that our rdr interval is constant so it's regular next thing i need to determine what's the qrs look like is it wide is it a big mama or is it narrow is it a little mama right how do i determine that again if i were to really measure this and we will look at this on 1280 kgs we measure how many little boxes are between the qrs complex here if there is greater than three small boxes within that qrs complex that is considered to be wide that's so if you remember how many seconds is one little box .04 seconds times three point one two seconds so if it is greater than .12 seconds it's wide if it's less than that we consider it narrow or maybe even indeterminate we'll talk about that later okay so in these we're going to say that that is narrow okay we're going to say that they are less than 0.12 seconds or three little boxes so so far we're bradycardic we have a normal interval okay our interval so it's regular we have a narrow qrs complex next thing is their sinus p waves what the heck does that mean so i like to go to lead two this is how i learned how to do it i look at lead two and i say what's my p wave doing is it upright i look here my qrs complex it has to be a p wave before the qrs it is upright then i say okay my avr has to be the exact inverse or opposite of lead two so let me go to avr is my p wave retrograde or inverted it is so if my p wave is upright in lead 2 inverted in avr and go down to my rhythm strip every p wave is followed by qrs which it is this is sinus rhythm okay so far what have i been able to assume bradycardic normal a regular constant a regular interval uh so regular rhythm it's a narrow qrs and sinus rhythm at this point in time i can then determine my pr interval so if you guys remember that's taking the p wave and the pr segment and measuring that i want to know is it prolonged is it normal in this case we're going to say it is less than 0.20 seconds it's going to be normal okay so we have in this case bradycardic regular narrow qrs sinus rhythm normal pr interval that is going to be a good way to pretty much systematically approach rate and rhythm now let's say that we take this into consideration we really take into consideration differential diagnosis which is super important when a person is going too fast or they're going too slow and utilize that system let's talk about that all right so let's use our system all right let's say we're taking a look at a 12 lead ekg is it going too fast too slow or normal let's say in this case the person is going too fast it's tachycardia next thing i want to know is the rhythm regular or irregular okay let's say it's regular what's my qrs looking like is it wide or is it narrow let's say in this case it's narrow if you go through that system that we just talked about that should give you a differential for narrow and regular tachycardias for narrow regular tachycardias there is three particular things that you need to try to figure out what it is as a part of your differential first one is sinus tachycardia how can i determine if it's sinus tachycardia is there sinus p waves is there upright p waves in lead 2 that are inverted in avr and a p followed by qrs atrial flutter and svt we'll talk about those a little bit later they can be very difficult to distinguish but these are the three things i need you to remember as a part of your differential next thing is it tachycardic is it irregular is it narrow there's a three more differentials i really need you to remember first one most common afib are they in atrial fibrillation do they have variable block so atrial flutter with a variable block whereas if you guys remember here with narrow regular it could be a two to one atrial flutter that produces a narrow regular tachycardia but if it's atrial flutter with a variable block that can produce a narrow and irregular tachycardia okay so afib variable atrial flutter and multifocal atrial tachycardia should be your differential for narrow irregular tachycardia what if you're tachycardic you're going too fast you have a regular rhythm but you have a wide qrs always always always v-tac v-tac v-tac until proven otherwise other things that it could be svt with a bundle branch block sinus tac with a bundle branch block or anti-drummic wpw but by far the most important wide regular tachycardia v-tac until proven otherwise the next one here is what if i'm going too fast irregular rhythm and a wide qrs polymorphic v-tac there's two types normal qt and prolonged qt atrial fibrillation with wolf parkinson's white syndrome that's a pretty serious one and a fib with a bundle branch block last but not least if we have a differential for bradycardia you still follow the same sequence and systematic approach we did above the only thing that's going to be a little bit different we'll talk about these in individual cases is that whenever i see bradycardia i go through the same system but i'm looking to break these into these groups are they having sinus bradycardia are they having an av block is it a junctional rhythm or is it a ventricular rhythm and we will go into great detail on these and really expand on this approach particularly when we get to this fifth step here in our cases okay so this is really what i want you guys to remember to approach every ekg the same way in determining the rate and rhythm for a 1280 kg all right engineers in this video we're going to be talking about the st segment in any particular abnormalities now you guys may be wondering zach why did we go straight from rate and rhythm right to the st segment shouldn't we go through all the other parts of the ekg like the different waves you could but here's the thing you want to focus your time on a 12 ekg and what's going to probably kill the patient the quickest right what would kill someone really quickly and arrhythmia that's why we got to go through and determine the rate and rhythm is this person having a deadly arrhythmia then the next thing that can really kill a patient is if they're having any ischemia or infarction and that's where we really got to take a look at those st segments very carefully because that's why we're going to focus on this next so st segments and their abnormalities why do i need to know this well the first thing that i need to know is is there any st segment elevation and i go through each lead i go all the way one two three avr avf v1 all the way to v6 and i look at that st segment is it elevated in any of those leads well here's the thing how much elevation do i truly need to be classified as st segment elevation is does sd segment elevation always equal mi not necessarily so let's talk a little bit about this sd segment elevation the way that you truly measure it is at the end of the qrs complex there's a point called the j point so if you could imagine here here's our qrs there actually is no s because an s wave has to come down through the isoelectric line and then come back up but right there at the end of this qrs complex is that little point there that goes into our st segment that there is our j point so you measure from the isoelectric line which would be right here how many millimeters above that isoelectric line until i get to the j point is there if it is one millimeter of st segment elevation in any of the leads okay except for v2 to v3 that's st segment elevation has to be in two contiguous leads but one millimeter st segment elevation in any of the leads except for v2 to v3 that is considered to be true st segment elevation it has to be two millimeters of st segment elevation in v2 to v3 in order for it to be truly st second elevation there as well okay so one millimeter everywhere except for mv2 to v3 has to be two millimeters okay if it is elevated can we automatically say oh it's a stemi no there could be a plethora of differentials to be considering on the top of the list though should be stemi some of the difficult things to sometimes really really do is is this person having a stemi or are they having benign early repolarization we'll have some good cases on that are they showing signs of pericarditis do they have prinz metals angina also known as vasospasm are they having a pe a pulmonary embolism is there a left ventricular aneurysm is there left ventricular hypertrophy or is there a left bundle branch block and we'll actually have a pretty good conversation about left bundle branch blocks in the setting of what a stemi and we'll talk about scarbosa's criteria for that but we're going to try to go through a bunch of ekgs to figure out oh we see sd segment elevation which one is it if you don't think about it you can miss it so always have a good differential and rule every single one of them out effectively this is what we need to know about sd segment elevation now just as important as st segment elevation is what if those st segments are sagging a little bit they're depressed that's also very important okay there's three different types of st segment depression i want you guys to be thinking about one is where you see here we have this sd segment it's kind of like uh sagging a little bit and it's kind of like down sloping a little bit if i were to draw a tangential line it's going to look like it's going this way that's down sloping as depression if i had a line here that's horizontal st depression and if i have this one here a tangential line that's up sloping st depression now st depression is just like we would say with st elevation find your j point where's my j point here's my j point for this horizontal one i wanna know with respect to my j point here's my j point how many millimeters how many small boxes is that j point below my isoelectric line if it is greater than or equal to 0.5 millimeters that's almost like a half a little box if it is greater than that in two contiguous leads and this isn't any lead that is considered st depression now out of all of these is there one of them that we should be more concerned with actually yes horizontal st depression can be a harbinger for actually concerning signs of ischemia so always always if you see someone with st depression and you see horizontal sd depression do not send them home because this could be a sign of ischemia the next thing though is to don't actually kind of like say what about upsloping that one's not that big of a deal and down sloping's not that big of a deal not necessarily true upsloping st depression there's a newer thing called the dewenter's t waves criteria which is almost a stemi equivalent if you see someone who has st depression and v1 to v3 with peak t waves this can be a harbinger of a very proximal led occlusion and a very scary type of stemi pre-coming okay so be thinking about that st depressions what do i need to know greater than or equal to 0.5 millimeters below the isoelectric line to the j point is st depression by definition and what could that tell me about and stemming should be at the top of the list okay very very important one but another big big one to think about is a posterior mine especially if you have st depression with upright t waves and dominant r waves in v1 to v3 think about posterior mind we'll go through a bunch of these cases the other ones to be thinking about is left bundle branch blocks left ventricular hypertrophy with strain pattern another really really big one very important when it helps determine is this person having a true stemi is you can see st depressions when someone's having a stemi and these are called reciprocal changes and the last one is a drug called digoxin toxicity and actually produces a very classical type of you or sagging type of down sloping sd depression and we'll show you some of those as well all right the last thing that i want you guys to think about is the only reason i threw it with the st segments is it's going to become very helpful we'll talk about it later we use this when we're trying to determine benign early repolarization from semis and i'll show you what i mean but is the last thing i want you guys to talk about is a j wave sometimes also referred to as an osborne wave in the setting of hypothermia but also hypercalcemia we'll talk about what i mean there but usually it kind of takes on this kind of like fish hook pattern so you have your q wave your r wave and then you're coming down you don't actually have an s wave because again what does the s wave have to do it has to go down through the isoelectric line and come back up so you don't actually have an s wave it stops here so it's kind of like the down slope of the r wave and you get this quick little blip quick little blip and then you go into the st segment and then to the t wave that little blip right there is called your j wave okay so this little blip right here is called your j wave why is that important if i have someone who has st segment elevations with a visible j wave and particular leads and we'll talk about this later this could be an indicator of benign early repolarization rather than st segment elevation mi okay so again what is a j wave it's a quick little short positive deflection on the downstroke of the r wave okay and it's going to be very helpful later when we're trying to differentiate benign early re-pull from a stemi okay but to be thorough because again if you don't think about it you can miss it j waves can also be seen not just a benign early repo but in hypothermic cases and hypercalcemia and a super rare condition called bragata syndrome where they have sd segment elevations right bundle branch blocks as well and sometimes a visible j wave okay very rare condition though but if you don't think about it you can miss it why am i going down to t wave so we started talking about rate and rhythm why because we need to know if there's any arrhythmias that can definitely kill a patient very quickly then we talk about st segment is there any ischemia and infarction right why is that important because if someone's having an mi that could also kill them but here's another big thing always look at the t waves as well any abnormalities in t waves particular types could also be a sign or a harbinger of impending ischemia or infarction so that's the next thing we're going to look at the big one that i really want you guys to remember is t wave inversions now t wave inversions are classified as when you have technically the t wave has to have kind of this deflecting or depression in a way that has to be at least greater than or equal to a millimeter below that isoelectric line or point okay so that's the first thing now you can have t wave inversions that can be considered completely normal if they're in v1 v2 your precordials or in lead three that's fine where am i most nervous if i see a t-wave inversion by itself just by its lonesome and avl i'm going to keep getting serial ekgs because you want to think about that that could be a sign of impending inferior wall am i okay think about that here's the other thing though think about your differentials with the t-wave inversion yes it could be a sign of ischemia what kind it could be potentially an inferior wall of mind or if you have these t-wave inversions that are in v2 v3 sometimes this can be a sign of the wellin's b criteria kind of type of ischemia is that something to be thinking about with a proximal led but other things to keep in mind for your differential is is there any left ventricular hypertrophy with strain is there any elevated intracranial pressure sometimes called cerebral t waves is there any bundle branch blocks left bundle branch block right bundle branch block is there any pulmonary embolisms right sometimes you see this with an s1 q3 t3 type of pattern we'll talk about that so big things to be thinking about when you see t wave inversions but again this is that big one i really want you guys to remember that avl okay the next one is the hyper acute waste hyperacute t waves very tall okay broad based asymmetrically peaked if you look at that so it doesn't have that beautiful kind of concave type of pattern that you'd usually see with it so hyper qt waves another way that you want to think about them if you can take your qrs complex and almost fit it into that hyper qt wave that is also a sign that it's probably a hyper qt wave so again broad based tall asymmetrically peaked maybe can even fit the qrs inside of it hyper acute why is that concerning hyper acute t waves definitely can be a sign of an early stemi especially here's a very very important one we'll talk about these when we get a look at the cases but if i see that t wave again normally you kind of want it to be concave but if it starts to look flat like almost straight as i'm going towards the upper upper slope of the t wave that is a sign of early ischemia okay a little bit a little bit concerning but the other thing to be thinking about is vasospasm so prinz metals angina the next one is a biphasic t-wave biphasic t-waves are again something you want to be thinking about a little scary if i see these in v2 to v3 okay the reason why is that kind of fulfills this wellin's a criteria which could be a sign of a proximal led occlusion so if i see a upward blip and then a negative blip i'm thinking about welln's a especially if it's in v2 to v3 if i see the opposite though where i see a negative blip and then a positive blip i got to be thinking maybe this could be hyperkalemia so check the potassium see if that's a little elevated okay so biphasic t waves think about those two types of things the the next one is a flat t wave flat t waves we have to kind of fit within the line of depression and normal right so we say depression is greater than one millimeter below the isoelectric point so a flat t wave has to be somewhere at least you can have you can go up to less than like negative one millimeter of depression and a millimeter of elevation or you know a positive deflection there so it has to be between negative one millimeters of deflection downwards and a millimeter of deflection upwards okay that's a flattened t wave flat t waves definitely a sign of impending ischemia definitely got to be concerned about those and also hypokalemia check their potassium all right the last one that i want to talk about here is peak t waves okay peak t waves they look like they would hurt to sit on okay so these are very narrow based very narrow based very tall and for the most part they're relatively symmetrically peaked okay so if i see a peak t wave obviously the first thing that comes to mind and everybody they would say oh hyperkalemia definitely could be also could be hypermagnesemia definitely could be one thing i really want to be thinking about though which is becoming a very big thing uh is the de winters types of t waves so this is actually considered to be a stemi equivalent if i see peak t waves in v1 to like v3 area and i also see an up sloping st depression i'm going to be a little bit scared for a proximal led occlusion it's called the d winter's t waves so be thinking about that yes peak t waves definitely can be hyperkalemia could be on the lower end hypermagnesemia but if you see this in v1 to v3 with an upsloping st depression be concerned for de winter's t waves which could be approximate led occlusion why are we going to the qrs wave well what have we covered up to this point we talked about the rate in rhythm we want to know is there any arrhythmias why because those can kill a patient very quickly then we went into the st segment is there any ischemia is there any infarction that's also a very scary thing then we look at the t waves why because the t waves could be sometimes an early sign of ischemia or infarction now what we're going to do is we're going to talk about qs complexes and we want to know a couple different things about them what do we want to know well the first thing we want to know is going back to our original thing from the rate and rhythm is is the qrs complexes wide or are they narrow right that's important remember what we said for a wide qrs we said basically if it is greater than 0.12 seconds in width which is three small little boxes that is considered to be a wide qrs right remember i told you though that sometimes if it's between 0.10 to 0.12 seconds it's kind of like we're on that teetering part of it being wide but it's not so it's kind of like an indeterminately wide qrs but let's just be simple greater than 0.12 seconds it's a wide qrs that's what we're going to stick with but just to be very very thorough just remember that there is an indeterminate point okay if i see a y qrs what do i need to be thinking about you got to have a differential you don't think about it you'll miss it right what do i think about first and foremost bundle branch blocks is there a left bundle branch block a right bundle branch block and we'll talk about the patterns that you can see with those in a second the next one hyperkalemia hyperkalemia can show up as anything anymore you know you don't always think it's going to you think it's going to show up as a peak t wave but sometimes it'll show up as a wide qrs complex sometimes as a junction of rhythm so always be thinking about that again hyperkalemia you see a wide qrs think about it what did i tell you always to think about with a wide and regular type of tachycardia v-tac right so if i see a wide qrs i also want to be thinking about vtec another one though that was in that differential of wide regular tachycardias was what wpw right but particularly we call it antidromic wpw so another one that you can think about again if you don't think about it you could miss it even though it might not be super common the other one is a pastry rhythm so someone has a pacemaker paste rhythms can sometimes produce wide qrs complexes so think about those as well and last but not least medications always have on the differential tricyclic antidepressant overdose as a potential for wide qrs's so wide qrs you see it you buy greater than .12 seconds three small boxes there's your differential make sure that you rule those out really quickly while we're here bundle branch blocks okay you want to be able to identify these on the 12 lead kg and we're going to look through a bunch of these but left bundle branch block when i look in v1 and v2 what i see is i see that my s wave is really really big i get this deep s wave there and then when i look in v5 and v6 i see this positive deflection with a little divot kind of almost making like a little m if you will and v5 and v6 okay so that is definitely very important left bundle branch block look at v5 v6 you're going to see kind of like this almost m type of shape with that actual qrs complex for right bundle branch blocks when i look in v1 to v2 you have this characteristic r s r prime pattern that you see in v1 and v2 and then in v5 and v6 you have your r wave coming down into your s wave but look how wide the s wave is there's a slurring of the s wave in v5 and v6 for right bundle branch blocks okay so that's a big thing to remember for left bundle you see kind of this m shaped very wide qrs and v5 v6 deep s wave and v1 to v2 sometimes you even get a little bifid kind of formation in v1 to v2 in that s wave you might even get a little bi-fit just like you see here in v5 v6 all right there's our bundle branch blocks the next thing that i need you guys to understand besides wide qrs is what else could be very significant to pick up as an abnormality is pathological q waves now you guys are like wait i thought q waves were a part of the normal qrs complex they are but you shouldn't see them in particular areas on the 1280 kg because they should not be there that could be a sign of ischemia or old ischemia or other negative things so we never see them in v1 and v3 if you ever see them in v1 to v3 q waves it's not normal regardless of their small or they're they're actually considered pathological regardless you see a q wave there not normal what do we consider to be a pathological q wave versus a normal q wave a pathological q wave it has to be very wide so if you were to measure that kind of distance there of the q wave it would have to be greater than .04 seconds which is a small little box or from the isoelectric line down to the peak of the q wave it has to be two millimeters deep or if i measured the distance from the isoelectric line down to the bottom of the q wave and then i measured the height of the qrs complex if that q wave is greater than or equal to 25 of the height of the qrs complex that's also considered to be a pathological q wave why is all of this important big thing is mis okay sometimes this can be a sign of a new acute mi or someone had an old mi in the past okay so these sometimes can actually occur acutely and they stay along for a very long time okay but also be thinking about pes with that s1 q3 t3 type of pattern think about left bundle branch blocks they can definitely produce pathological q waves and lvh with a strain pattern okay all right so the next one that i want to talk about is low voltage qrs complexes these sometimes can be kind of overlooked and for the most part they're not too serious in the particular clinical setting but if i see someone who is short short of breath or tachycardic i got to be a little bit concerned for a pericardial effusion right so how do i determine if someone has a low voltage qrs there's a lot of different ways that you can do this one of the ways that i like to look at them is i take and i add up the r waves and lead one two three if it's less than 15 millimeters that could be a sign of low voltage qrs i can do the same kind of concept here but i do it in v1 v2 v3 and if it's less than 30 millimeters that also could be a sign of low voltage qrs complexes why am i worried about that well definitely at the highest point of concern is pericardial effusion there's something that's blocking the conduction or the electrical activity from getting from the heart to the electrodes what could that be something is blocking the conduction it could be fluid pericardial effusion it could be fat obesity it could be air copd or it could be that the heart is not being able to generate enough of an action potential or conduct action potentials through it maybe it's because the heart is really floppy and weak heart failure or super rare but sometimes if you don't think about it you can miss it infiltrative diseases deposits within the conductive conductive tissue of the heart like amyloidosis and sarcoidosis okay so big thing to think about here low voltage qrs complexes really be on high alert especially in the clinical setting of shortness of breath and tachycardia for pericardial effusion all right the next thing that i want to be thinking about with qrs complexes is i want to look at the pattern of them as i go from v1 to v6 because it tells me about two different things it tells me about the r wave progression is the r wave progression as i go from v 1 to v 6 not very good or is there a dominant r wave which is present in the early parts of the precordial chest leads so what the heck does road progression mean it's very simple you see how generally normally as you go from v1 to v6 the r wave should exponentially start to really increase but let's say that it's just only incy benzy types of increases that you see as you go from v1 to v6 so it's not a great increase usually in v5 v6 those r waves should be pretty dang big if they're not too big and the s waves are also still pretty big in v5 and v6 and i don't see that nice steady increase going from v1 to v6 that could be a sign of poor r wave progression and that could be a sign of an anterior mi or it could be a sign of right ventricular hypertrophy with strain and we'll look at some cases like that okay the next one is a dominant r wave this is the one that i would be a little bit more concerned with if i look here and i see the r waves in v1 v2 v3 they're big and they're not supposed to be really big in v1 to v3 those are supposed to be smaller r waves and bigger s waves that's a part of the normal kind of cardiac axis there if i see that they're bigger in v1 v2 v3 and on top of that i see st depression upright t waves i'm going to be really nervous for posterior mi okay so that should be at the top of the list whenever you see kind of this dominant r wave in v1 to v3 along with st depression and upright t waves think about posterior but make sure you rule out first look at old ekgs do they have a right bundle branch block do they have right ventricular hypertrophy and anything that can cause right ventricular hypertrophy so again rule those things out first but be on high alert for a posterior stemi okay last but not least for abnormalities with the qrs complexes is let's talk about what the heck this lvh left ventricular hypertrophy and rvh right ventricular hypertrophy means and what it looks like so i look at these again similar to bundle branch blocks i look at v1 and v2 v5 and v6 so again you have an r wave here s wave here r wave here s wave here i will add together the height in millimeters of the r wave in v5 and v6 or one of them v5 or v6 add the r wave in millimeters to the s wave in millimeter in v1 or v2 if when i add those two together that comes to greater than 35 millimeters that is a sign of left ventricular hypertrophy we'll go through plenty of cases on these and pick them out what could that be indicative of it could be indicative of any really kind of persistent strain on that left side of the heart hypertension aortic stenosis many different things right ventricular hypertrophy it's the same concept but it's the opposite so i look at the r wave r waves aren't supposed to be big in v1 v2 or v3 right particularly v1 and v2 but if my r wave is bigger than my s wave and i take and i add up the millimeters of my r wave in v1 or v2 and i add it to my s wave which is not supposed to be big in v5 or v6 but i add that to the millimeters of my s wave and v5 or v6 and that ends up being greater than 10 millimeters that is a sign of right ventricular hypertrophy you know what else adds to that diagnosis if you have this is if they also have associated right axis deviation and we'll show you what that means what could right ventricular hypertrophy be due to anything that's putting strain on the right ventricle if someone has maybe a pulmonic stenosis or they have pulmonary hypertension due to some underlying lung disease like copd or interstitial lung disease things like that could cause some right ventricular hypertrophy all right engineers so in the next part of our systematic approach we've already covered what we've covered the rate in rhythm we've covered the st segments we've covered the t waves we've covered the qrs wave analysis now it's time to talk about the qt interval in the abnormalities that may be present there why is that important well the qt interval if it is prolonged more more concerning it could be something very pathologically you know very serious that we need to be able to pick out very quickly so first thing we need to determine is how do we know if it's a prolonged qd interval remember how do we measure the qt interval you start right there before the q wave starts to go down and then you go all the way until after the t wave okay and then you measure that distance now generally we say that qt intervals that are particularly greater than about 460 milliseconds in females is considered to be definition long qt prolonged qt greater than 450 milliseconds and males is considered to be by definition a prolonged qt however to be very very specific the computer and you should also use particular formulas there's a bunch of different formulas like for example bizet's formula to calculate the corrected qt interval to give a more accurate representation of what the true qt interval is at varying rates okay that's important so always check your qtc and then utilize those numbers accordingly determine is this truly prolonged now why is this important well the reason why this is important if someone has a very prolonged qt interval the concern or the risk is that this can eventually throw them into a deadly arrhythmia called torsades to points which can present as what's called a polymorphic ventricular tachycardia so we need to be able to pick that out to prevent that from happening a good rule of thumb is if you don't want to go ahead and be specific and measure all these things you can take the qt interval and it should be about half the preceding r to r interval okay so that's another thing to be thinking about if you see a prolonged q and a qt interval you calc you based it upon the qtc or you based it upon the half of the preceding rdr interval you're worried about the risk of developing torsades what are your differentials that you need to be thinking about that could be causing this by far one of the serious ones that you need to be thinking about is is there any medications because i could quickly just discontinue those how do i remember them anti-arrhythmics antibiotics antipsychotics antidepressants antiomedics those are medications that can definitely have a very intense risk on that qt interval so discontinue those medications the other things that you need to be thinking about is electrolyte abnormalities are they low in potassium are they low in magnesium are they low in calcium because those could be particularly things that if we fix it it'll fix that qt interval another really concerning one is ischemia is this a sign of ischemia is the person having a myocardial infarction i need to be able to pick that stuff up as well so once you see a prolonged qt think about your differentials if you don't think about it you could miss it rule those things out and treat accordingly not as significant but just to be thorough we should think about short qt intervals so what is that defined as technically it's when you have a qt interval that's less than 350 milliseconds i'm not super concerned if you know this but for thoroughness think about it what you'd want to be thinking about is some of the opposite for prolonged qt if it was hypokalem if it was hypokalemia hypomagnesemia guess what it would be due to hyperkalemia hypermagnesemia and on that off chance sometimes if someone's taking digoxin some digoxin toxicity could be another thing that's causing that as well so again these are the things i want you to be thinking about in your systematic approach here looking at the qt interval and then the abnormalities now let's go ahead and talk about the next thing which is the p wave pr interval and any abnormalities present there our systematic approach is what's the rate what's the rhythm is the st segment elevated or depressed are there any t wave abnormalities are there any qrs wave abnormalities what's the qt interval is it prolonged or is it short and now we're at the point where we can say all right we have some time let's look at those p waves and the pr intervals and see if there's any abnormalities there what kind of abnormalities should we be looking for and keep our eyes peeled open for well the first thing is you want to be thinking about signs of atrial enlargement right atrial enlargement left atrium larger or sometimes even bi-atrial enlargement so what does this look like well the first one let's talk about right atrial enlargement so right atrial enlargement what i do is i'll take a look at my p waves and lead two and you can even extend this to 3 and avf if you want to but i like to look just in lead 2 and i'll take a look at my p wave is my p wave a little bit bigger than it should be in other words if i look at the height is my p wave greater than or equal to 2.5 millimeters above the isoelectric line because if it is that is definitely a big p wave an abnormal p wave and that could be indicative of right h or enlargement to add on to that to enhance your actual diagnostic seals there look at v1 so if you look at 2 or 3avf you see a big p wave greater than 2.5 millimeters in height and you look over at v1 and you see this kind of biphasic p wave where the upward positive deflection is bigger than the negative deflection that also could be a sign of right atrial enlargement what else could you do though you could do an echo and see if there really is some radiator enlargement but right at your enlargement what could be causes of this think about valvular stuff is there something going on with the tricuspid valve it's stenotic is the pulmonic valve stenotic do they have a lot of strain on that right side of the heart because of something going on with the lungs those are all things to be thinking about okay left atria enlargement same thing look at lead two do i see a p wave that's pretty big but more importantly looks like a camel's hump it's bifid if i see a bifid p wave that's located in lead two and again you can send it to three and avf i just like lead to the best i see a bifid p wave and the point between those two points the camel hump is greater than .04 seconds one little box that is considered to be a bifid p wave indicative of left atrium enlargement to enhance that diagnostic ability though go to v1 do you see a biphasic p wave oh i do so not only do i have a bifid p wave and lead 2 but i also have a biphasic p wave in v1 what's my upward deflection bigger than my negative or what or is it vice versa the negative deflection is bigger than the positive deflection in that biphasic p wave that is indicative of left atrial enlargement okay left here enlargement what could be causes think about something going on with the valves on the left side of the heart is there mitral stenosis is there aortic stenosis or is there a lot of systemic hypertension going on that's causing things to back up into that circulation towards the pulmonary circulation right so these are things to think about for the atrial enlargements all right so now let's talk about the pr interval and any abnormalities that may be present there so short pr interval it's less than 0.12 seconds again so three small little boxes okay if it's shorter than that that could be indicative of wolff parkinson's white sentry you know wolf parkinson's white syndrome does have that shortening of the pr interval it has a wide qrs it also has that delta wave as well so sometimes you may be able to see wpw another thing is premature atrial contractions so sometimes if you have a pac an ectopic area somewhere that ate you that fires quicker and it's closer to the av node that may produce a shortening of that pr interval as well now these are interesting but by far what you really really want to take away from the pr interval abnormalities is when it's prolonged those are the real big meaty ones that you want to think about especially when it comes to heart blocks if the pr interval is greater than 0.20 seconds that is technically the definition of a prolonged pr interval that's actually one large box remember that one large box so what do i think about definitely if it is long you want to be thinking about heart blocks first off is if it's a first degree heart block first degree heart blocks they have a prolonged pr interval but it's the same prolonged pr interval throughout the entire length of the rhythm strip if it's a second degree heart block it has to be mobitz one because those also have a prolonged pr interval that gets longer and longer and longer down that rhythm strip and then last but not least is a third degree heart block those have prolonged pr intervals but they're variable they could be short at one point in time but when we say short they're still long and they can be longer they're all over the place but they definitely have the ability to have prolonged pr intervals and third degree heart blocks all right engineer so we're at the last part of our systematic approach to 12-lead ekgs and that's talking about the cardiac axis and any abnormalities that we may be picking up in this portion of the lecture so at this point we've talked about rate and rhythm we've talked about the st segment we've talked about the t waves we talked about the qrs wave we went to the qt interval we even went to the p wave the pr interval and all the abnormalities that can come up there now we can take a look at cardiac axis and any abnormalities that may pop up there so we have to ask ourselves the question what the heck is cardiac axis so to really make it the basic bare minimum that you really need to know here let's talk about what normal axis is okay normal cardiac axis and then after that we'll discuss the abnormalities so normal cardiac axis can be based upon primarily two leads within your 12 lead ekg lead 1 and lead avf now what you're going to be looking for is using your thumbs to help you in this process all right your left thumb is going to be lead one your right thumb is going to be avf let's start first off looking at the most important thing the r wave in lead one is it primarily is there positive deflection of the r wave or is there a negative deflection a big s wave in lead one let's take a look here and lead one if we were to imagine this is what it looks like that's the r wave that's that's definitely up so i'm going to put my left thumb up for lead one go here to avf let's look at this first one don't mind this for right now look at this one avf is the r wave as their primary positive deflection yes it's both thumbs up both thumbs up that's good that's normal baby that's normal axis however you can still have a normal axis in one other scenario same thing let's say that your lead one r wave is positive deflection upwards primarily avf though there's a predominant kind of s wave the s wave is bigger than the r wave and avf well uh oh now my left thumb is up my right thumb is down that's left axis deviation if your left one's up but here we got to be very very careful if avf is ever down lead one is ever up always take a second look at lead two the reason why is you base the the decision if it is left axis deviation or normal axis based upon the presence of the r wave in lead two if the r wave in lead 2 is upright then it is normal axis so to recap that part if you're a positive deflection lead 1 negative deflection avf you check lead 2 and lead 2 has a positive deflection it is a normal axis okay now let's talk about times where the axis deviation is to the left to the right or extremely to the right so the first one is left axis deviation so the electrical vectors are going to be more profound on the left side of the heart or in this case left ventricle usually so what happens is the lead one let's use our thumbs here lead one if there's an upright deflection of the r wave that's up avf there's a downward deflection of the s wave primarily that's down like this right so that is what seems to be left axis deviation but what do you always have to check whenever you have lead one up avf down check lead 2. what's lead 2 look like it is primarily an s wave a negative deflection there so that is left axis deviation if it was upright primarily the r wave was up it would be normal but it's not there's a primary negative deflection there so that is left axis deviation so lead one up avf down check lead two it's also down left axis what could be causes of this left axis deviation if you have a bundle branch particularly a block in that left bundle branch that could potentially cause a left axis deviation because now the electrical activity has to come from the right side to the left side it could be lvh where the ventricles on the left side are thicker and causing more electrical activity to get pushed to that side or it could be inferior mice or hyperkalemia okay that is something i want you to think about the next one is right axis deviation so use your thumbs again right axis what's my lead one doing oh that's primarily a downward deflection with the s wave okay what's my avf doing that's a primary upwards deflection of the r wave so left thumb down right thumb up which thumb is up the right thumb that's right axis deviation so usually whatever thumb is pointing up is telling you the axis you just have to be a little bit careful when you do left axis deviation check that lead too but again right lead one's down so left thumbs down right thumbs up that is right axis deviation don't worry about lead two you already know it's a right axis deviation so what could be the problems here so there could be a right bundle branch block there's a block in the right bundle branch that's causing the left side of the heart to have to bring electrical activity to the right side or there's a thickness of that right ventricle causing more electrical activity to get pulled to that or it could be an anterior my or vtac ventricular tachycardia where the tachycardia is actually originating particularly in the left side of the heart and it's getting pushed towards the right side of the heart all right extreme right axis deviation extreme right axis deviation again use your thumbs here lead one what's it looking like well there's a primary negative deflection of the s wave avf primary negative deflection of the s wave the both thumbs are down wow that's pretty extreme right so that is extreme right axis deviation when both of them are pointing down don't worry about lead two what could be potential causes that that right ventricle will be thick right so thick right ventricle pulling lots of electrical activity to it that's going to cause an extreme deviation to the right side the electrical activity the mean electrical vectors if you want to think about the qrs uh vector primarily v-tac there's a electrical focus that is maybe developing within the left side of the heart particularly left ventricle and that electrical activity spreading towards the right side or severe obesity if someone's really really obese it actually can push the diaphragm up and push the heart maybe the apex instead of it being towards the left maybe a little bit midline maybe even a teensy bit to the right which kind of affects that mean qrs vector causing that extreme right axis deviation so i think this gives you the bare minimum the big things that you need to know to be able to determine what's the cardiac axis and what could be the potential causes of these abnormalities all right engineers i hope this made sense i hope that you guys did enjoy it i hope it helped as always ninja nerds until next time [Music] you