Effects of Ischemia on the ECG

greetings everyone in this video we're going to explore the effects of myocardial ischemia on the EKG tracing let's review quickly the different components of the EKG and the different waveforms and what each represents so the P wave represents atrial depolarization followed by the QRS complex which represents ventricular depolarization so atrial and ventricular depolarization takes place and is represented graphically as the P and QRS complex following the QRS complex is the ST segment and following the ST segment is the T wave and both the ST segment and T wave represent repolarization of ventricle ER tissue so at what point does ventricular depolarization end and ventricular repolarization begin and the answer to that is in this magic point right here known as the J point and the J point is nothing more than the junction between ventricular depolarization and ventricular repolarization so when the myocardium is ischemic a couple changes occur on the EKG but most are isolated to the J point itself the ST segment and the T wave so when looking for myocardial ischemia on the EKG tracing we're going to focus on the J point we're going to focus on the ST segment and we're going to focus on the T wave and certainly there will be some other changes to the QRS complex perhaps even maybe to the P wave and PR segment and interval but the majority of the findings that will have during myocardial ischemia are going to be limited to the J point the ST segment and the T wave so let's explore each one of those in depth so the first thing we want to do is be able to identify and recognize where the J point is exactly so as we said the J point signifies the end of ventricular depolarization and the beginning of ventricular repolarization another way to look at it is that the J point is where there's a departure from the QRS complex into the ST segment and T wave there's usually an acute angle that happens at this departure point in this case the J point is located right here in this tracing there are certainly some other changes in these waveforms and we'll explore those in a second right now we're just looking to make sure we can all find the J point here's another example and forgive me for the quality of the tracing I don't know why it came out that way the J point in this case is this acute angle that takes place at the end of the QRS complex and before the st-segment that's the junction the end of ventricular depolarization and the beginning of ventricular repolarization let's do one last example the J point so the J point in this example is right about here and again that signifies the end of ventricular depolarization off to the left and everything to the right of that point is ventricular repolarization being able to find the J point is critically important because we're going to next evaluate the location of that J point against other elements on the EKG trace so in this case there are a couple rules to follow the first rule is under no circumstance is it ever okay to evaluate the location of the J point against the PR interval or PR segment it is never okay to do that because the PR interval may also be up or down meaning that it has departed from the isoelectronic or baseline and we wouldn't want to compare two variables against one another to determine if one of them has moved instead the rule is that the J point is only and always evaluated against the isoelectric line so let me place the isoelectric line in this case where that blue line is and I'm also going to place a line where the level of the J point is and that's just about right here next what we want to do is we want to determine where the J point is in relation to the isoelectric line in this case it's pretty easy to see that the J point is well below isoelectric in fact it's about 3.5 or 3 millimeters below the isoelectric line so one of the things that can happen with the J point is that the J point can drop down below isoelectric we tend to refer this to this as ST segment depression but in reality the better way to describe it is J point depression let's take a look at the other option that can happen the other thing that can take place here let's establish our isoelectronic again here's our isoelectric line let's locate where the L of where the level of the J point is it's just about there and then we'll evaluate the location of the J point as it relates to the isoelectric and in this particular case we'll see that the J point is elevated compared to the isoelectric line and so this is the second option that can occur during ischaemic change and that is that the J point can depart from isoelectric and it can rise above the isoelectric line we colloquially refer to this as ST segment elevation but again the better way to describe this would be to call it J point elevation so the two changes J point depression or ST segment depression or the J point can elevate J point elevation or ST segment elevation both of those things can occur during myocardial ischemia next we want to look at the shapes of the ST segments themselves and one of the ways we can do that is by drawing a line from the end of the QRS complex to the tallest point of the T wave and so we're going to do that here and we're going to identify a specific pattern so when we find the end of the QRS complex it's kind of hard to determine where exactly the J point is here so instead of looking specifically for the J point we're going to evaluate the shape of the ST segment and T wave in its early stage to determine if the pattern of ischemia exists so in this case when we draw a line from the end of the QRS complex to the very tallest point of the T wave if any of the ST segment or T wave lies above that line that we drew that is a pathological finding that is most consistent with ischemia on the EKG this is also referred to as convex ST segment so this is a really important finding and convexity convex ST segments are always abnormal and convex st segments are those st segments that present with an ST or T wave that lie above a line drawn from the end of the QRS complex to the tip of the T wave convexity and the ST segment is always bad news it always indicates that there's a problem and almost always that problem is an ischemic change let's look at some other ST segment shapes that can occur this next one is a flat ST segment just as though we did in the previous example if you find the end of the QRS complex in this case the j-point is very clearly identifiable and you draw a line whoops let me go back here and you draw a line from the J point to the tip of the T wave if the ST segment or early phase of the T wave lie right on the line that you draw this is a horizontal section this is a flat section and ST segments and T waves are never supposed to be flat another example of that is in this right-hand illustration again I apologize for the quality of the tracing if we draw a line from the end of the QRS complex the J point through the ST segment you'll notice that that ST segment is also flat flat ST segments are always abnormal so we talked in the previous one previous example that convex ST segments are always a abnormal and now we're going to say not only are convex ST segments abnormal but flat st segments are also abnormal flat ST segment always a bad sign there are only two things that cause ST segment flattening and those involve myocardial ischemia or hypo kal Samiha and so when we look at these ST segments when we're looking at the shape of the ST segments convex ST segments are bad and flat ST segments are always abnormal findings next we're going to look at the third possibility in this third possibility as we find the J point very clearly identifiable here and go to the tip of the T wave what we find here is that the ST segment actually dips below this line and typically when we find an ST segment that is concave concave concave ST segments are almost always normal findings or their normal variants of benign conditions they don't typically identify ischemia on the tracing that's not always a hundred percent or conclusive so it's sometimes possible to have acute ischemic change that creates a concave ST segment in fact this particular tracing an example that I'm using is from a patient with myocardial ischemia so convex ST segments and flat esti segments are always abnormal findings concave ST segments are typically from benign presentations but they can also be from ischemic change so we have to be careful in with the concave presentation because it can be benign or it can be a more sinister presentation shut such as myocardial ischemia all right now for field providers for folks who want an expedient method of looking at the ST segment without spending too much time on it and determining if it's okay or if it's bad this is my recommendation to you draw some eyeballs on it and so what I mean by that is find your ST segment and early part of the T wave and put some eyeballs on it and if this frowns at you if you get a frowny face out of it right this is always bad and badness on the EKG think of ischemia so put some eyeballs on the ST segment and T wave if they frown at you that's bad the next possibility is to put some eyeballs on those two flat s T segments that we looked at just a little while ago again these don't look like very happy st segments flat st segments are also bad think ischemic change so concave st segments our next presentation if you put some eyeballs on this guy it's actually pretty happy and so happy st segments typically mean benign condition but not always and so we have to be careful with this guy frowny faces and sad faces are always bad happy faces are usually benign but can sometimes be related to ischemic change next we want to look at the ST segment itself and the direction or the slope in which it's traveling so there are three possibilities it can be an upward or an up sloping ST segment it can be a horizontal ST segment or it can be a Down sloping ST segment so horizontal ST segments and downsloping ST segments are always bad and again when you think of badness on the EKG you're thinking about myocardial ischemia up sloping ST segments can sometimes be okay but they have to be rapidly rising you normally see this like a much more acute almost vertical approach you'll see this sometimes in stress testing with a person who's got a healthy heart and has a completely normal stress test the ST segment will dip a little bit below isoelectric because there's the person is exercising there's a little bit of a supply and demand and bounce and so the myocardium is just repolarizing a little bit differently in this case and in this example however the slope of the ST segment is really lazy so these three slopes that are illustrated on this chart are all bad and all indicate ischemia so a lazily rising up sloping ST segment is bad horizontal ST segment always bad and down sloping ST segment always bad always signs of myocardial ischemia really really important to identify on the EKG last but not least we want to look at the T wave itself and we want to see the changes associated with the T wave so there are going to be four really important changes to look for the first one is a peaked or tented T wave the next one is going to be a broad-base next we're going to look for the symmetry of the T wave and we're going to determine if the T wave is hyper acute now let's explore each of these independently so when we talk about a peaked or a tented appearance a normal T wave is supposed to have a nice gradual upslope and a rapid return to baseline it's not supposed to look like a TP or to be peaked or tented as is the case with this particular example the next thing we want to look at is we want to look at the base of this T wave look how massive and broad this T wave basis it really shouldn't be that broad it should be much more narrow so a peaked or tented T wave a broad-based T wave always tell us about a problem that's going on now we look at the T wave symmetry so if we were to evaluate the T waves left and right legs with respect to a vertical line that we draw that wasn't very vertical let me try that again little bit better if we now evaluate this right leg and compare it to this left leg you'll see that both kind of mirror one another and so this talks and speaks to the symmetry of the T wave and as we discussed up here a normal T wave no matter where you put a vertical line there should be no symmetry right to left there should be a nice gradual up sloping ST segment into the T wave and a rapid return to baseline so symmetrical T waves are always an abnormal finding last but not least we want to evaluate if the T wave size is hyperacute and when we talk about hyperacute T waves we talk about a T wave whose amplitude exceeds half the amplitude of the QRS complex so if it's greater than half the amplitude of the QRS complex we refer to that as a Piper qtwave and in this case you'll see the T wave is actually taller than the QRS complex not by much but it's actually taller than the entire complex so this illustration shows us peaked or tented T wave it shows us a T wave with a really broad base it shows us a symmetrical T wave and it shows us a T wave that is hyper acute in nature these four findings are critically important to recognize on the EKG tracing because they tell us about EKG badness specifically they tell us about myocardial ischemia so what do we do with all this and let's summarize what we talked about so when you approach the EKG after you've done your rhythm identification and interpretation if you're looking for ischemic change you're going to look for the J point you're going to look at the ST segment you're going to look at the T wave specifically with the J point you're going to determine is there J point depression or elevation if there's ST segment depression or J point depression or ST segment elevation or J point elevation these are both abnormal findings so the presence of either one of these or both in certain EKGs is abnormal so we're really going to want to be able to recognize that this is an abnormal finding this speaks to ischemic change next we want to look at the ST segment itself is the shape convex is it flat another way to ask is is it frowning or sad appearing if you put I ball Zahn it or is it concave remember that convex and frowning are always abnormal these speak to myocardial ischemia and concave is sometimes abnormal but usually associated with benign conditions lastly we want to determine what the shape of the T wave is and there are four specific things we're going to look for the first is is the T wave peaked or tented in appearance next we want to inquire about the base of the T wave is there a broad-base oops I did that last time too is there a broad-base next we want to look at the T wave symmetry symmetric T waves are always abnormal last but not least we want to look at is the T wave hypercute and again that was is the amplitude of the T wave in excess of half of the QRS amplitude so the presence of ST segment depression and or ST segment elevation the presence of convex or flat ST segments the presence of peaked or tented broad-based symmetric and hyper QT waves all identify the presence of myocardial ischemia

Channel: Chris Touzeau

Views: 212,889

Keywords: ischemia, EKG, ECG, 12 Lead, Ischemic ECG

Id: MCRYcLArHp0

Length: 21min 4sec (1264 seconds)

Published: Sat Dec 26 2015