all right so now that we've discussed the coronary circulation and reviewed the electrical system of the heart and how it works it's now time to move into actually learning about our 12 lead EKG the coronary circulation and the conduction system will come into play when evaluating our 12 leads but we need to start off with some introductory information first to establish a good foundation of knowledge as we move into the actual interpretation so let's discuss that here [Music] all right you guys welcome back to another video Lesson from ICU Advantage my name is Eddie Watson and my goal with this channel is to try to give you guys the confidence to succeed in the ICU out there by taking these complex Critical Care subjects and making them easy to understand I hope that I'm able to do just that and if I am I do invite you to subscribe to the Channel Down Below when you do though make sure you hit that Bell icon and select all notifications that way you'll never miss out when I release a new lesson now if you enjoy watching these videos and you do want to earn CE credits while doing so make sure and head on over to icuadvantage.com forward slash Academy and join the ICU Advantage Academy over there you can watch these great videos Earn CE credits while you're doing it as well as have access to audio only versions of these lessons as well as access to the notes which I am currently in the process of revamping and making them even better you can find links to this as well down in the lesson description and the comments that said if you don't need the CE credits but you do want some of the extra perks like access to the notes as well as audio only versions of the lessons you can't join either the YouTube or patreon membership and get access to that stuff over there again I'll have links to both of those down below as well alright so this is going to be a series of lessons taking a good look at our 12 lead EKGs I'm going to break the lessons up into multiple lessons on various aspects of our 12 lead interpretation I am going to cover a lot of information here in this series but also know that this series is not going to be going super in depth we're going to cover information that's mostly pertinent for your evaluation and interpretation working in the ICU but know that there's definitely much more to learn Beyond what's presented here at the end of this series you should have a good understanding of what's happening with our 12 lead as well as have the knowledge needed to evaluate what is shown for our most common concerns so to start things off let's do a quick review over the basic components of our EKG waveform here we have an example of a single waveform for a complete cardiac cycle this essentially tells us about the electrical activity of the heart so first we have our isoelectric line and this is the Baseline of our EKG tracing this really represents no electrical activity now we have our P wave here which is going to be our atrial depolarization then we have our QRS complex here which is our ventricular depolarization and then finally we have our T wave which is our ventricular repolarization and we do actually have atrial repolarization that takes place but it is pretty minimal on our tracing and it is buried within the QRS complex and thus it's not something that we typically see now from here we have certain intervals and segments that play an important role in getting measurements for the first one is going to be our PR interval this is measured from the start of the P wave to the start of the QRS complex and this tells us the time from atrial depolarization until ventricular depolarization then we have the width of our QRS complex measured from the beginning of the Q to the end of the S and this tells us the time it took for The ventricle to depolarize then we have our QT interval and this is going to be measured from the start of the QRS complex to the end of the T wave and this is the time it takes for both ventricular depolarization and repolarization to take place and then finally we have our ST segment this segment here represents when and the ventricles are depolarized with no electrical movement taking place before repolarization and this should be along the isoelectric line like we see here all right with that out of the way let's move on and talk about the EKG system and really give you the understanding of the different parts and how it all works so first we have our electrodes and these are what measure the electrical signals these are the little stickies that we put on the patient and then from there we hook up the the wires or the different leads to those electrodes so we have positive and negative leads something we call bipolar which can go figure be both positive or negative depending how we're using them as well as a series of positive leads now this is important because the direction of electricity in relation to where the positive lead is determines how we're going to see a waveform so let me kind of give you some examples and show you this here so if we have electrical activity that's moving towards a positive electrode then we're going to see a positive or upright waveform now if this electricity is moving away from a positive electrode then this is when we're going to see a negative or downward waveform and then if the electrical activity is actually traveling perpendicular or alongside the positive electrode then this is when we get a biphasic waveform so if it's perfectly perpendicular we're going to have this equophasic or isoelectric waveform so our our positive and negatives are going to be the same but then as we start to shift the angle and either going more towards or more way that this can actually change how the waveform appears and we can have smaller positive with a larger negative or a larger positive with a smaller negative and that kind of determines how we see our waveforms now for the electrode placement it's really important that in order to have accuracy of our EKG recording we have to have proper electrode placement or lead placement so the improper positioning here is going to change the appearance of the waveform and this can either mask issues that we have or falsely present other ones so for our preparation ideally patient's hair should be clipped the site should be cleaned with alcohol and we should use skin prep this is going to greatly reduce the amount of artifact that's present understandably though time may not really allow for this we do want to elevate the head to around 30 degrees for the patient again if possible and then we do want to try to keep the chest bare so we don't want to have sheets blankets gowns clothing over the top of the electrodes that said it's also important that we keep the patient warm because if they're shivering and moving that this is going to introduce artifact as well so the patient's going to want to be still now for the actual placement of these electrodes there's only 10 physical electrodes that we're going to be placing but these together are going to give us our 12 leads that we're viewing so here we have our patient's body and let's go through the different lead placement that we have first is our right arm lead typically the white lead and our typical five lead bundle this one's going to go on the right arm distal to the shoulder next we have the right leg lead again typically our green lead this one's going to go on the right leg distal to the hip although typically we try to put this below the knee next we have the left arm this is going to be the black lead this will go on the left arm distal to the shoulder there we have the left leg or the red lead going on that left leg distal to the hip again typically below the knee next is going to be our V1 lead this is typically the brown lead on that five lead bundle and the positioning for this is going to go fourth intercostal space on the patient's right sternal border now for v2 this is also going to be fourth intercostal space but this is going to be just across the sternum on that left sternal border now for the remaining V leads it's helpful if we place V4 and V6 first because these are actually going to be reference points for V3 and V5 so V4 is going to go down the fifth intercostal space but this is going to be midclavicular line then for V6 this is going to be mid axillary so along the patient's left side but we want to make sure that we have this along the same horizontal plane as V4 so at the same level as V4 now going back to V3 that this one we're going to place midway between V2 and V4 and then V5 we're going to place midway between V4 and V6 again important that we're along that same plain as those other leads important to stress it's important that V4 V5 and V6 are in a line along that horizontal plane all right so now that we have the properly placed leads we do need to understand about the different views that we get from these leads so let's talk about the plane that I've been talking about these different planes really we can think of planes as ways to divide the body I always imagine this like a magician who cuts a person in half the blade of the magician would be one of the planes and there's three primary anatomical planes we have the vertical or frontal plane and so this is dividing the body into anterior posterior or front to back so think of this one as running head to toe dividing the body into the front and back next we have the axle or horizontal or transverse plane and this divides the body into inferior and Superior so top and bottom to help visualize this one this would be the same plane that the magician magically cuts a person in half and then finally we have the sagittal plane and this one divides the body into left and right so again head to toe but this time left and right instead of front to back now of these three planes the two that we really care about for our EKGs are the vertical frontal plane so dividing front and back and the axial horizontal plane dividing top and bottom half of our leads that we have are going to be looking at the heart in the vertical frontal plane and the other half will be looking at the heart and the axial horizontal plane so when it comes to these actual leads we have different groups of leads that we have so the first is going to be our limb leads and these are going to be leads one two and three these three leads are looking at the heart along that vertical frontal plane and Lead one we're going to have the positive electrode on our left arm and we're going to be looking from the right arm to the left arm for lead two that this is going to be looking to the left leg from the right arm and then lead three is also going to be looking at the left leg this time from the left arm then we have our three augmented limb leads these are the remaining three leads that are still looking at the heart along that vertical frontal plane and we can really think of the augmented limb leads as being the average view between two different leads so first we have AVR are being right this is going to be looking at the right arm but combining the view from the left arm and left leg so you can kind of think here if we look at this if we draw a line between the left arm and left leg and then the Midway point of that to the right arm is how we're looking now for AVL this is left so here we're going to be looking at the left arm but combining the look from the right arm and the left leg and then finally avf where the F stands for foot is going to be combining the look from the right arm and the left arm down to the left leg and the purpose of these augmented limb leads is they give us a different angle of view from the traditional limb leads the more angles we have the more perspective we have on the heart and to really kind of put all this into perspective if we take an image of the heart part here and let's draw a circle and divide it up so we have different angles of our views we can see if we look at lead 2 on our body here going from the right arm to the left leg that angle when we put it up against the heart here coming down at about 60 degrees this one's roughly about the same direction that we would expect the electricity to be traveling in the left ventricle and then from there you can just look at the direction that we're looking at things at the different of the six leads and then put those angles onto sort of our pie chart that we have here all right so from there let's talk about our precordial or our chest leads these are going to be V1 through V6 and these six leads are now looking at the heart from the other important plane the axial or transverse or horizontal plane so this is that plane dividing the body from top to bottom these leads give us a good look at the area of the chest over the heart and really give us a more complete view of the harp so if we take a cross section here across the horizontal plane um we can see we've got the heart here we've got V1 through V6 along the the chest here now each of these leads though is the equivalent to measuring from a theoretically calculated reference point this is something that we call Wilson Central Terminal and we're going to go from that which is located about here on the heart out to each one of these precordial leads the way that it does this is it gets the calculation by utilizing the three limb leads so right arm left arm left leg these three combine to make a triangle and then the middle of this triangle is this Wilson Central Terminal all right so now let's talk about artifact so if you're having artifact in your tracing you really need to correct this issue to ensure that we do get a good clean picture when we're evaluating our EKG if you have artifact in any of the limb leads you can usually determine which electrode is the culprit by evaluating two different leads typically we're going to have artifact and two leads if one of the limb lead electrodes is the problem so if we think about the leads that are involved in getting the particular recordings where we were drawing out earlier if we're seeing artifact in leads 1 and lead two we want to check the right arm because that's typically going to be the electrode that's causing the problem if we're seeing artifact in leads one and three the left arm is typically the culprit and if we're seeing artifact in leads two and leads three then the left leg is typically going to be our culprit here correcting the artifact in these limb leads are also thus going to correct any artifact that we see in the augmented limb leads because they're using the same electrodes so first you want to fix any limb lead artifact first then you can move on to the precordial leads and these ones are actually easy to fix because you can easily identify which lead is the culprit if V3 is showing artifact then fix the V3 electrode all right so now let's move on and talk about our EKG paper and this is essentially a standardized background that we have for our 12 lead EKG to print out on and this is both on paper and electronic versions The standardization of this allows us to compare between different EKGs of the same patient as well as between patients and it helps us draw conclusions based on the size and position of the waveforms so now let's actually talk about the 12 leads that are going to print on on this paper so again remember we've got our positive negative and biphasic that we talked about positive is going to be above the isoelectric line meaning the electrical activity is moving toward the lead that we're viewing negative is going to be below that isoelectric line meaning electrical activity is moving away from the lead that it's viewing and then biphasic being both above and below means electrical activity is partially moving towards and then partially moving away from the viewing lead and this applies to our P wave our QRS complex as well as our T wave and then depending on the lead and the direction of the wave that we see in that lead can actually tell us a lot about many different things and these are going to be things that I discuss more later in the series so looking at our paper here we have our limb leads on the left and our precordial leads on the right we typically are going to see three per column and thus the first two columns here on the left are our limb leads with the First Column being our normal limb leads so one two and three with the next column being our augmented limb leads AVR AVL avf the next two columns are the precordial leads and they just go in numbered order so V1 V2 V3 and then V4 V5 V6 then at the bottom we're going to have our Rhythm lead and this is going to run full length across the bottom now typically this is lead to but this is something that we can change in the settings as well as sometimes we can have multiple full length rhythms showing across the bottom typically we're going to have time marker hashes either at the bottom or the top of the paper the total length of this full Rhythm strip though is 10 seconds so we should have two three second marks and a four second Mark and these marks as well as the boxes that we see the big and small boxes as well as just knowing the total here being 10 seconds that these all help us to determine the rate of our patient's Rhythm so remember 25 millimeters so five big boxes is equal to one second of time moving left to right so speaking of that let's talk about the paper size and the measurements that we get so our standardized EKG paper also has a standardized speed at which it prints and that is the 25 millimeters or five big boxes per second the standardization also takes place for the voltage measured of the electrical activity so this is shown as the amplitude or the height of the wave going either up or down and here 10 millimeters so two big boxes is going to be equal to one millivolt all right and so then for the boxes themselves we have both our large or big boxes as well as our little boxes a large big box is composed of Five Little Boxes each little box measuring one millimeter by one millimeter giving us for a big box five millimeters by five millimeters and so here the height is going to be equal to the amplitude or voltage and remember that I said two big boxes is one millivolt thus one big box is going to be a half of a millivolt then the width of the big box is going to be time so how long the electrical activity is taking place and remember I said five big boxes is one second so take that one divide by five one big box is equal to 0.2 seconds and then for those little boxes um we know that there's five of those within each big box so for the height of a little box it's going to be equal to 0.1 millivolt and the width of a little box is going to be point zero four seconds and again for these we just took the the values from a big box and divided it by five to get these values now at the top of our paper we're usually going to have some more information here on the top left is typically going to be our patient information on the top middle we're going to get calculated values for our different measurements so the rate the PR interval the the QRS complex with Etc as well as our axes which I am going to be going over all of this more in the next lesson in future lessons then at the top right we're usually going to have our computers interpretation as well as once it's been manually reviewed the reviewer can make annotations or changes for their own interpretation again this is going to come later in the series and then finally I want to talk quickly about the relationship between the leads and the Heart regions and we do this through something that we call contiguous leads so and what this means is that we have leads that are looking at the same part of the heart and I'm going to go through and group them out and divide them up and use different colors to to Really show the groupings but really you're just going to need to memorize this pattern that I'm going to show you this way when you're looking at a printout of the EKG you know the different regions that we're looking at so first let's actually start down in the the bottom corner here so leads 2 3 and avf I'm going to highlight these in green and these are going to be the inferior portion of the heart then we have leads 1 and AVL here that these are going to represent the high lateral then we have V1 and V2 that are going to be our septal leads V3 and V4 anterior leads and V5 and V6 low lateral now that said when we're looking at our pre-cordial leads we're really going to also consider any two leads that are near each other also being contiguous and the reason for this is if you think about that that cross section I showed you with those leads going across there even though like if we look at V4 we consider that anterior and V5 we consider that low lateral they're actually pretty close together so they're looking at a similar part of the heart and really one of the big purposes for memorizing and knowing this is that when we're looking at especially patients who are having Mis if we know what vessels from the coronary circulation feed what regions of the heart you can then see if we see changes here in particular leads we would know what part of the heart is impacted and thus generally which blood vessel is involved in this again this is stuff that I'm going to go more in depth in the future lesson but I just wanted to kind of cover the the basics and give you an understanding of what that meant all right so we covered a lot of information here for our introduction to doing our 12v EKG interpretation knowing this information is really going to build that solid foundation for the future lessons in the series and are really going to help bring it all together and help it to make sense for you this is going to give you the why for when we're going through these future lessons and we're just talking about the changes that we see referring back to this lesson here will give you that why on why things might be looking different so I hope that you guys found this information useful if you did please leave me a like on the video down below that really helps YouTube know to show this video to other people out there as well as leave me a comment down below I love reading the comments that you guys leave and I try to respond to as many people as I can make sure you subscribe to this channel if you haven't already and a special shout out to the Awesome YouTube and patreon members out there the support that you're willing to show me and this channel is truly appreciated so thank you guys so very much if you'd be interested in showing additional support for this channel you can find links to both the YouTube and patreon membership down below head on over there and check out some of the perks that you guys get for doing just that as well as check out some of the links to other nursing gear as well as some awesome t-shirt designs I have down there as well make sure you guys stay tuned for the next lesson that I release otherwise in the meantime here's a couple awesome lessons I'm going to link to right here as always thank you guys so much for watching have a great day