welcome to the first step in the 12-lead interpretation first thing I want to ask whenever we talk about 12-lead interpretation is where exactly does the term 12-lead come from basically the term 12-lead comes from the 12 different views of the heart that we can acquire on the EKG even though we only put 10 electrodes and 10 wires on the patient through advanced circuitry and mathematics were able to take a look at the heart at 12 different angles what are the heck's axial leads we have two different kinds of leads actually we have hex axial leads and precordial leads the hex axial lead - the leads that you get whenever you place limb leads on the patient that means you put a lead on the right arm left arm right leg and left leg the hex axial leads are leads one lead two and lead three lead AVR lead AVL and lead a VF we're going to review each one of these shortly the precordial leads are leads v1 v2 v3 v4 v5 and v6 why do we need to have a firm understanding of interpretation of twelve leads well I have three separate reasons why I've actually come up with number one advancing in treatments with the advancement of research and technology we have a better understanding of the pathophysiology of myocardial ischemia and infarction since we have a better understanding we can now provide a more efficient and effective treatment plan to patients who are actually having MI or ischemia or any kind of acute coronary syndrome in the past morphine beta blocking agents calcium channel blockers and other treatment plans that are now considered standards of practice were not part of the normal treatment plans with mi now because of better research and technology we have a better outcome of patients with these conditions of acute coronary syndrome number two EKG machines can interpret a 12-lead better than healthcare providers when most people are handed to 12 lead the first thing they tend to do is look at the interpretation at the top provided by the computer many providers of health care have become crippled with the advancement of technology and its ability to interpret these results for us in some situations this may be called for but at other times we need to look at the results of the tests to confirm the interpretation and/or diagnosis the example I like to use is the arterial blood gas if you were to look at the results of a blood gas and the pH just read hi what exactly does that tell you if you are trying to treat metabolic acidosis and you don't know how acidotic the patient is because the ABG just reads metabolic acidosis or if you sent a complete blood count off to the lab and the results came back as bad how's a person expected to treat these results the answer is you can't sometimes we as professional health care providers need to look at the intricacies of the results to better understand the overall diagnosis so that we can personalize the treatment plan as much as possible also if a person can interpret a piece of information about our patient better than we can then I believe it's time for us to elevate the level of our education finally the computer can sometimes provide incorrect or ambiguous interpretations I've seen interpretations on the EKG that have read nonspecific t-wave abnormality consider lateral ischemia so if you see this do you treat the patient as if he or she was having an acute coronary syndrome or not if you trust the interpretation on the EKG only and you don't know what the computer is looking for or even looking at then how are you supposed to treat this patient with such an ambiguous statement if this is the case then you will have to treat every single patient as if he or she is having a heart attack because the interpretation said that you have to consider ischemia so for these three reasons people should be able to interpret the bumps and squiggles as it were on a 12-lead and not just read the interpretation at the top first I'd like to review the X axial lead x' the first three leads we're going to review our lead one lead two and lead three these leads are considered bipolar because you have to place to physical poles or electrodes on the body a positive electrode and a negative electrode this will detect the electrical impulses of the heart so let's look where these leads actually come from first we're going to look at lead one to acquire lead one what you're going to do is you're actually going to put the positive electrode over here on the left arm typically it's on the left wrist but sometimes people put it somewhere up here on the upper arm as well you're going to put the negative electrode over here on the right arm well you have to put a ground so you're going to put your ground electrode down here on your left leg or left foot now the reason you need to know the location of the positive and negative electrodes is because the positive electrode is actually considered the camera if you were to actually look up here there's a camera right here so if you were to look at the camera this is the camera where you are actually looking from but you have to have a destination so the camera is always looking from the positive electrode to the negative electrode so in this case you're actually looking from the left arm over to the right arm now let's look at lead to to acquire lead to what you're going to do is you're actually going to put the positive electrode down here at the left foot the negative electrode is still going to stay up here on the right arm the ground electrode is going to come over here onto the left arm so what you're going to do is you're still looking from positive to negative so now you're actually looking up in this direction towards the right arm the next few we're going to look at is lead 3 and lead 3 what you're going to do is you're going to keep the positive electrode on the left foot but you're going to move the negative electrode over here to the left arm the ground electrode is going to be kept is going to be moved over here to the right arm you're still looking from the left foot but now rather than looking at the right arm you're looking up this way towards the left arm those three leads are the first three leads that were really ever researched so what we're going to do now is we're actually going to talk about the other three leads that are part of the heck's axial leads leads AVR AVL and AVF now these leads are a little bit different because you don't actually use to physical poles on the body or to physical electrodes on the body like you do with leads one lead to and lead 3 what they've done here is that they've actually created a theoretical negative lead that goes in the middle of the body and it's usually the heart that is actually considered a this theoretical negative now when they go through this process of mathematics and circuitry to actually create this theoretical negative or the central terminal what happens is the signal is degraded significantly so what they actually have to do is they have to augment the voltage or amplify the voltage so that you can see the lead the exact same way that you would see leads one two and three now these are considered unipolar leads because there's only one physical pole or one physical electrode on the body and that's the positive electrode the negative electrode is not a real electrode it is actually the heart that's what they consider the negative electrode so let's go ahead and look at lead AVL so we're going to start off here and as you see you actually have lead one view basically we have a positive electrode here you have your negative electrode over here generally speaking you're moving in this direction but remember you're always looking from positive to negative so what were to happen if we were to actually move the negative electrode down to the central terminal the angle of your camera will move with it so now you are not looking from the left arm to the right arm you're actually looking from the left arm down into the center of the heart so you're looking in this direction which has now given you another that's supposed to be an arrow another view of the heart it is now given us a completely different view of the heart all because we just moved the negative electrode from a physical negative electrode on the right arm to a theoretical negative inside the heart remember that this negative electrode down here in the middle right here this is called the central terminal the same principle applies to AV F we're going to place the positive electrode down here on the left foot we're going to place the negative electrode up here on the right arm to give us lead to but if we move this negative electrode right here from the right arm down to the central terminal it will actually change the angle of our camera it will change it from a lead to view down into an AV F view so now we're actually looking from the left foot directly up at the bottom of the heart finally let's look at AVR what we did with AVR is we actually took the positive electrode we placed it over here on the right arm this is the only lead of the hex axial leads where the positive electrode is on the right arm the negative electrode is going to be over here on the left arm if we were to use this lead this is a polar opposite of lead one but what we're doing here is we're actually getting another view so we're going to move the electrode down into the central terminal what this does is it actually gives us another view of the heart so if you look at this just by moving the negative electrode around in the positive electrode as well we now have six different views of the heart if you were to look here we have leads 1 2 & 3 now we've created an AVR AVL and an AV F this is why this is the hex axial plane it gives us an up-and-down and left-right view of the heart so what I'm going to try to do now is explain where all of these leads are actually looking now if you were to actually look at the heart itself we'll pretend that to heart for a second lead to normally looks up in this direction well that's actually how we see it on paper that's lead to on lead 3 we look up in this direction that's how we see it on paper lead 1 looks in that direction but that's how we see it on paper what the Machine actually looks at is the Machine goes from the left foot for lead 2 and it goes up this way through the heart and then around over here to the right arm so the Machine doesn't actually look outside the heart this way it looks up through the heart and then to the right arm if it wants to get lead 3 it looks up through the bottom of the heart and then it curves over here to the left arm lead 1 actually starts over here and it goes down into the heart and then back up to the right arm so what we actually have I'm going to draw another heart here is here's your left foot this is your right arm this is your left arm so really lead to supposed to be a 2 starts here and curves this way lead 3 starts here and curves this way where lead 1 starts here dips down and then comes back up well this doesn't make as much sense as a triangle so what they did was they decided to take lead 1 on paper looks across this way and keep it as a flat line rather than a curved line and they just moved it down into the central terminal and that's actually what they did over here you take lead 1 and you move it down here and then what happens is you have lead 1 going through the heart looking in this direction this is so we have a better understanding of what the leads are actually looking at lead two they move in so now you actually have lead two looking up in this way lead three they have looking up in this way now what happens here is that you actually have a different view of what we're looking at here so I went ahead and erased all the ink off the slide so that way you can kind of see what I'm looking at so lead one we are going to go ahead and move down and put it at the heart as it were as a central terminal lead two we're going to move that one over and put that at the central terminal and then we're also going to move lead three so that way we're looking at straight lines we don't want to look at curved lines we actually want to look at straight lines now these are the first three leads that were researched leads one two and three but if you remember what happens now that we've actually moved this triangle into the central terminal right here here's our central terminal right in the middle now if you remember this is our theoretical negative down here this is where we can actually change the camera views so we change the camera views now AVF if you remember looks directly up from the bottom through the central terminal so this is where we get our three views of leads one two three and AVF AVL is starting at the left arm and actually going through the central terminal as well and of course if we put AVR up on the right arm it will also look through the central terminal now we actually have all the leads of our hex axial plane all intersecting through the heart at the central terminal and this is what we actually see now we're going to discuss the precordial lead plate the pro cordial leads are placed in very specific locations on the chest they are considered unipolar leads which means they have a physical positive electrode but the central terminal or is considered the theoretical negative take two and it looks at the heart from the anterior left ventricular aspect all the way around to the left side so we're going to go ahead and discuss placement now it's very important that you follow the proper placement procedures and a lot of people asked me in the past do you actually put these electrodes exactly where you're supposed to and my answer is if it's possible for me to place these electrodes exactly where they're supposed to go I do it every single time and the reason for that is because improper placement can actually change the interpretation of your 12-lead if the leaves are not placed in the right spot or if they're backwards or you put the v1 on the v2 spot it will drastically it could drastically change the interpretation of your 12-lead and potentially your treatment plan so let's go ahead and find out exactly how you should place these electrodes first of all you want to place your finger at the top notch of the sternum now where you're actually placing your finger is right up here at the super sternal notch right here the here it's called the jugular notch you place your finger up there to find that don't press too hard because the trachea is right below that the next step is you actually move your fingers down until you feel the horizontal ridge right there when at the angle of Louie this is where the manubrium actually joins the sternum of or the body of the sternum so you're going to start up here the next thing that you're going to do is you're going to move your finger slowly down until you actually feel a slight horizontal Ridge or elevation so what you're going to do is you're actually looking for this little spot right here that landmark which in this case is called the manubrium sternal joint it's also sometimes called the angle of Louie as well so once you find this spot right here this is your second landmark over here this is your second landmark you're going to start here you're going to migrate your fingers down until you actually feel that joint right there the next step that you're going to do is that you're going to find your joint right here the angle of Louie and you're going to migrate over here to the left because your first placement is going to be on the left side as you move your fingers across you will actually run into this articular facet of the second rib so once you find this spot right here this bump that you feel right here on the outside of the sternum is actually going to be the second rib the next thing you do is you locate the second intercostal space once I've actually found the second rib right here the hole that my finger goes into right here is a second intercostal space our goal is to find the fourth intercostal space so you just use your fingers and you migrate your way down from the second intercostal space to the third and then into the fourth intercostal space so here's my second intercostal space there's my third intercostal space here is my fourth intercostal space this is the spot that I'm actually looking for right here once I have found the fourth intercostal space I put the electrode v1 right here as close to the sternum as possible now in the past people have asked well what happens if there's a lot of tissue there if there's lots of breast tissue due to fat people or women's breasts or whatever as long as you stay close to the sternum here there's not a lot of adipose tissue over the sternal body right here at all so what you can do is stay close to it you will still be able to feel at least the sternal rib joint and then find the intercostal space as well once we've actually found v1 you don't have to find all those landmarks again we already have v1 placed all you have to do is take your fingers and move over here right about the same area on the other side the sternum is going to be the place where we're going to put v2 so we place an electrode so far we've found v1 now we've placed vitu our next step is that we're going to find the left mid clavicular or sagittal line in the fifth intercostal space we're going to use the midclavicular line which means I'm going to start here and I'm also going to look over here and I'm going to go from the midclavicular line down to the fifth intercostal space once I find the mid-clavicular line fifth intercostal space I'm going to place v4 now notice I skipped over v3 the reason for that is because you have to find v4 and v2 to find v3 once I have actually found v4 and I know where v2 is placed I just place an electrode directly in the middle of these two electrodes and that will give me the three so I kind of have to backtrack I have to go skip over v3 find v4 and then backtrack to get to v3 that is the proper lead placement now v5 is actually placed at the same level as v4 so here we have V 1 V 2 this is V 3 V 4 now from here I'm just going to place these in a direct line in this direction I don't curve up I don't curve down it's in a straight line v4 v5 and v6 v5 is placed at the same level as v4 but we're replacing it actually is what's called the anterior axillary line so basically what we're saying is the front part of the armpit here you find the crease right here where the aren't on the anterior axillary and you place v4 I'm sorry you place v5 same level as v4 at the level of the axillary line that is where v5 would actually be placed to place v6 like I said you're going to stay on the same level as v4 you're not curving but you're going to use mid-axillary the middle of the armpit that's your intersection to find v6 just remember sometimes you might actually have to move the arm out of the way in most cases you will have to remove the arm or I'm sorry move the arm out of the way if you do not move the arm out of the way you are probably placing v6 in the wrong spot so to summarize all of the procore do lead placement v1 is placed on the right side of the sternum fourth intercostal space right here v2 is placed fourth intercostal space right side of the sternum please remember this needs to be placed as close to the sternum as possible the three is placed midway between the 4 and V 2 so v3 is going to be placed over here v4 is placed in the left midclavicular line fifth intercostal space please do not use the nipple as a landmark and the reason for this is because not all nipples on the human body are placed in the exact same spot older people are going to have different nipple locations and younger people and if women have any kind of breast augmentation done then the nipples can pretty much end up in any direction so please do not use tissue as a landmark use the clavicle the midclavicular line as the actual landmark the v is going to be placed at the left anterior axillary line at the same level so if this is the axillary line I'm going to say that v5 is going to go right here at the same level as v4 and v6 of course is midex Lari line same level as v4 since I can't draw it it's going to end up over here on the side you might have to move the patient's arm out of the way and if you don't then you're probably placing v6 in the wrong spot several people have asked me in the past what happens if there is actually tissue for example breast tissue on men or women that is actually in the way where should your placement go well in the ideal situation it should actually go underneath the tissue unfortunately sometimes that is not a realistic option but you can place the electrode as close as possible now let's go ahead and look at where the procore deol lead placement is supposed to be I want you to look at these leads and take a look at the heart here the heart is actually in the middle and as you can see right in the middle you actually have the central terminal which is the big negative right there in the parentheses that's a central terminal now the pro cordial leads are actually the unipolar leads that are looking from the surface of the body all the way into the middle of the heart so if you place these electrodes in the proper spot these are the general areas where you're actually going to look we're going to start off with v1 v1 is actually going to look from the right I'm sorry the left side of the sternum directly into the heart right here v2 is also going to look from the right side of the sternum V in the fourth intercostal space directly into the heart now ideally these are actually considered septal leads because primarily you are looking at the interventricular septum that's where the central terminal is actually located the three on the other hand is actually considered an anterior left ventricle not the anterior aspect of the heart so we're actually looking over here at the anterior left ventricle this is the anterior aspect of the heart we're not leave v3 is looking at the anterior left ventricle the 4 is also looking at the anterior left ventricle of the heart as well so v4 is kind of looking in this direction my line is a little crooked as we get around 2 V 5 V 5 is actually looking at the left lateral wall of the left ventricle the 6 is doing the exact same thing if we look at V 6 it's over here looking at the left lateral wall as well so if somebody is having an anterior lateral wall MI it's affecting this whole area right here then we can clearly see it on v3 v4 v5 and v6 now if you look at these little dotted lines here these little brackets what this basically means is that v2 will not only look at the septal leads that's what it's primarily looking at but v2 has a little bit of an anterior view of the heart as well so you could see changes in v3 and v4 but you might actually see changes in v2 as well that might not necessarily mean that there is a septal problem it could just be bleed over as it were from the anterior leads the same thing can happen over here in v4 you can have a lateral wall MI affecting v5 and v6 but you have a little bit of v4 because not only is v4 primarily looking at the anterior leads it is secondarily looking at the lateral leads as well now let's go ahead and take a look at what part of the heart each one of the 12 leads are looking at and how you will actually see them on the paper now traditionally the EKG paper has one of two layouts the vertical and the horizontal views it's more common to use the horizontal layout so that's pretty much what I'm going to stick to here in the horizontal layout what you're actually going to have is an EKG that is printed from left to right the first three leads that are printed are leads one two and three these are the first three leads that are actually printed they will be followed by printing AVR AVL and a VF then they're going to print v1 v2 v3 and then v4 v5 and v6 will then be printed now all of these rhythm all of these twelve leads are all laid out pretty much exactly like this this is considered a standard layout it is possible that some people may change this standard layout but most of the time the first thing you do when you pick up a 12-lead and you look at it this is the layout that all of the leads are going to be located so if you remember back on the picture whenever I was showing you what we were looking at lead one actually looks at the left lateral ventricle lead two looks at the inferior wall lead three looks at the inferior wall AVR looks actually kind of at the right atrium but we're going to talk about AVR later on AVL looks at the left lateral ventricle or left lateral wall a VF looks at the inferior wall v1 and v2 our septum or septal leads the three is actually the anterior left ventricle v4 is also the anterior here left ventricle v5 and v6 are the left lateral ventricle so if you wanted to look at the inferior wall of the heart what you would do is you would actually look here at two three and AVF this is where you would want to look if you are looking at the inferior wall of the heart if you wanted to look at the septal you would look here at v1 and v2 if you actually wanted to look at the left lateral ventricle well you wouldn't just look here at v5 and v6 you would also look over here at one and AVL because all four of those leads actually look at the left lateral ventricle and then of course you also have v3 and v4 which look at the left anterior so depending on where you want to look will depend on what areas that you actually are looking on the paper last thing I want to talk about here is the rhythm strip the rhythm strip usually is going to be printed down here on the bottom at the same time that all of these leads are printed across the top now the nice thing about the rhythm strip it actually helps you interpret the rhythm and normally the rhythm strip is either lead to or very commonly lead v1 now the reason that it has been lead v1 is because in the past before we had twelve leads that were everywhere they were only located pretty much in the hospitals and they weren't really located much place much other places what they would do is they would print up a rhythm strip using only leads one two and three and then if we wanted to look and see why we actually had a wide QRS we could determine a bundle branch block or ventricular tachycardias using lead v1 since we didn't have v1 on the monitors what we used to do is actually use a lead called MC l1 now this is a modified chess elite as one of the term that's actually called as a modified chess lead what you would do is you would actually switch the monitor to lead three and then you would actually move the left foot lead from the left foot up to the V one location this is actually what would happen to look at the V one lead so what would happen is V one would be the positive the left arm would still be considered negative but it would get us as close to V 1 as it would so rhythm strips are usually for that reason lead to or lead v1 so now what do the leads actually look at well lead 1 an AVL v5 and v6 if you're looking at a standard 12 lead lead 1 and AVL or your lateral v5 and v6 or your lateral they're always going to be located right there leads to 3 and AVF of course we're looking at the inferior wall of the heart all three of those leads are going to be located in the lower left corner of the 12-lead and they are connected to 3 and a VF AVR is actually right lateral and the main reason that we have an AVR really is to confirm if the electrical conduction is going in the proper direction because AVR is actually a unipolar lead what you have is a positive electrode up here on the right arm the heart is the negative the central terminal you're actually looking in this direction what you actually can use AVR for is to confirm that the electricity is traveling in the wrong direct in the proper direction because you're going to have an inverted P wave an inverted QRS and an inverted T wave all of this is going to be in your AVR lead if you have a positive something in your AVR lead then you know that the electricity is traveling in the wrong direction that's about the as useful as I want you guys to know for AVR so let's move on to the interventricular septum to really note the interventricular septum you want to look at v1 and v2 they're always going to be located right here the left ventricle the anterior left ventricle is always going to be v3 and v4 these are the ones that are really the only ones that are split v5 and v6 or lateral one and AV L or lateral to 3a VF for inferior v1 v2 septum these two split up on the on the EKG paper but I guess there's nothing we can do about that and of course v5 and v6 are your other lateral leads way over here looking way over here on the left lateral the last topic I would like to discuss is how exactly does the computer grab or acquire this 12-lead the reason I like to cover this is because many people are not sure how this actually happened and sometimes they can become confused when they see artifact or love or other electrical anomalies actually print it up on the EKG paper as the computer prints the 12-lead it doesn't just copy and paste the first set of complexes in the EKG it's actually running a rhythm strip of electrical activity on the heart now what that means is whenever you hit the print the EKG button some of the machine's not all of them will actually sit there for a few seconds and say that it is acquiring the reason that it is acquiring is that because it is recording everything and then it will actually analyze and print the EKG when it prints the EKG is going to print it in a certain fashion as the picture comes across the screen the stars that appear horizontally or to the left and to the right are complexes that occur as the heart is beating in real time as the stars appear vertically up and down that is the exact same single complex in three to four different views or leads now what this means is if you were to look at lead 1 for example up here would be lead 1 right here if you look at lead 1 you have an orange star lead 1 white star and lead 2 and a red star and lead 3 what this is is this complex right here is the exact same electrical beat that occurred in the heart at this point in time which means that this is the exact same beat in three different views of the heart simultaneously at the same time since it was actually printing these three beats right here are related to each other but this complex and this complex are not related this is actually called the temporal relationship what that means is if you look down here and see this beat right here corresponds with every single beat above it this is your rhythm strip down here on the bottom this is lead to because here's your lead two and white stars here is going to be lead two which are your white stars printing now what you actually have is every single beat above or complex above that one correlates this correlates all of these correlate with each other all of these correlate with each other so do these these as well these as well and these as well all of those correlate above but you have no correlation between those right there none of these actually correlate at all this is the temporal relationship now the reason that we do this is because if you need to interpret a rhythm and you have all kinds of ectopy or something else is going on you need to know what is actually the underlying rhythm if you look at these stars over here if you didn't know that this complex and this complex were actually premature Beats or ectopic beats of some kind you might not know that because it is in a different lead it's actually switched but if you were to look down here and okay this is what your normal complex is supposed to look like but what happened as it came over here you had two ectopic beats occur the exact moment that you were actually printing up v1 v2 and v3 but then you went back to normal now using my rhythm strip I can say you know what I cannot use these beats in my rhythm or my 12-lead interpretation because they are not normal beats I hope you enjoyed the presentation and I hope it wasn't overly confusing for you if you do have any questions about this please feel free to contact your lecture instructor at any time