Very good video! I am a patient with a misdiagnosed EKG that stopped an operation because it showed that I had a silent heart attack sometime in the past. I had to go to a cardiologist for a second opinion so that I could proceed with the surgery. The cardiologist compared the two EKGs and explained that the operator of the first EKG had positioned one of the leads incorrectly. Good news for me! I was very concerned that in today’s modern medicine this type of error not only cost my insurance company more money but worried me for more than a week. Your videos where very instructive, I am an electrical engineer and I understood the basics of the EKG and was able to understand the conclusion of the cardiologist. Thank you!
Amazing! Thank you so much for making these. The graphics are perfect and precise, and your method of teaching is deliberate and clear. I'm a first year IM resident and I have been struggling with EKG's. I feel like my medical school really did a poor job at teaching how to interpret EKG's. But your videos are bringing me up to speed in no time! Thank you so much, and keep them coming!
@@docgirl13 I hope you have got your answer by now. but i will like to reply to this comment for those who are reading this to find answer. the ECG machine travel at a rate of 5 big boxes in 1 sec , so it will travel 60sec x 5 big boxes =300 big boxes in one minute. your heart beat relation to big boxes can be written as = 1 heart beat / x no. of big boxes ( where 'x' represent the no of big boxes the machine travel during the duration of 1 heart beat ) so if you multiply both you get heart beat in relation to 1 min i.e 300/ x no of big boxes hope this help
Sir Thanks a lot. U r the most efficient teacher I have ever seen. Thanks for putting ur valuable time and knowledge for us. And I will remember for u ever 🙏 thanks and love from india
When discussing the equiphasic approach to determining the QRS axis, the "2nd lead" mentioned in Step 3 is a little bit of a confusing term; could use the term "orthogonal lead to equiphasic lead" @17:59
Nice explanation of the quadrant approach; for the equidiphasic approach I enjoyed the explanation on 12ems; a video tutorial showing the actual steps would have been nicer, words/ pics are for some kinda difficult here, esp. if multiple arrows are used; and for 17:06 (I got asked) "3. If the qrs [...]" --> in other words: If one uses a ruler and puts it on a 90° degree angle in resp. to the lead where you have been observing the equi(di)phasic wave, you do not know, via which direction you are supposed to follow the ruler, i.e. you do not know if you need to look on the top of the hexaxial system or check the bottom side; to know this, you check the qrs complex on the ECG paper of the second lead (in fact it is the lead that is kinda covered by your ruler); if the qrs of this second lead is positive, then you need to check where the positive pole of the very same second lead (ruler) is - to get the location of the positive/ negative pole of a lead just check the picture of the hexaxial system on e.g. wiki, it's denoted there with a small arrow pointing upwards (positive pole) or a small arrow pointing downwards (negative pole) - and then, since we were looking for the positive pole, check the degrees written next to the positive pole; et voila that's it (+-15°).
Very instructive video. My only objection is that the method you propose of calculating the numerical axis is a bit confusing, if one is not overly familiar with all the axes. I think a more easy and simple way is to look for the perpendicular axis to the isoelectric lead, and then go to the two leads at the two ends of this perpendicular. The lead with the the most positive wave is the one which defines the axis. Many thanks for your videos.
Hey all, I've got 2 questions specifically regarding axis determination and possible left axis deviation. For context I am a final year med student. Greatly appreciate any insights, thanks! 1) During med school, we had a number of lectures and tutorials regarding ECG interpretation. Here, two separate consultant cardiologists recommended to me to primarily use lead I and lead II to determine axis, and skip using lead aVF entirely, although I was aware that some resources recommended using lead I and lead aVF. From this video, I now understand that specifically comparing lead I + II vs lead I + aVF and noting whether both are positive allows us to determine between -30 to 0 deg vs 0 to 90 deg. So my question is, given this, is there any particular reason why different resources suggest using different leads? Especially given that most people in the population would have an axis of between +90 to +15 as mentioned earlier in the video. Thus to me it actually makes more sense to use the approach outlined in this video, starting off with lead I + aVF and then moving to lead I + II. 2) In the example shown at 16:06, lead I + aVF suggests possible LAD, but checking lead I + II confirms normal axis, suggesting an axis of between -30 to 0 degrees. My question is, if this is the case, why would the amplitude in lead aVF be so big? Given that the vector of electrical depolarisation is fairly perpendicular to aVF? Wouldn't it make more sense that the amplitude be smaller than it is shown, and probably closer to being equiphasic? Thanks :)
Thank you so much doctor for explainig very well. I have a simple question in 19:29, Why not directly see what lies 90 degrees away from Lead II, why we use aVF?
Divya, with each of the 6 frontal leads, there is only 1 other lead that is 90 degrees away from it: I and aVF are a perpendicular pair, II and aVL are a perpendicular pair, and III and aVR are a perpendicular pair. Once you've identified the equiphasic lead, you simply look at the one lead that is 90 degrees away, irrespective of whether it is clockwise or counterclockwise. For example, if I is the equiphasic lead, you should look at aVF, whereas if aVF is the equiphasic lead, you should look at I. For a graphical representation of what I'm describing, you can look at my video on EKG leads at the picture around 10:15.
***** Thank you for responding :)! according to Dr Eric's response to this post-he's saying it shouldnt matter and I just go to the perpendicular lead? as in avL if lead II is equiphasic and lead I if avF is equiphasic? But youre saying move to the adjacent lead thats positive?
Good evening doctor and an amazing teacher, in the third example for determining axis at 20:18 if we use the vector method and actually put values in tan inverse (aVF/lead I), the answer comes close to around -45 degrees. While your method seems absolutely correct, can you please help point out the mistake in my method?
thank you very much your videos has been a great help to me .. i wish if i knew about them earlier at my college years where i struggled my way thru ECG .. thank u again :)
14:23 as for the quadrant approach what if Lead I is positive and Lead aVF is equiphasic ? thanks for the videos and the time you dedicate for teaching!
The shorter duration of the sample, the less accurate it will be - particularly for slower rhythms. But if the goal is only to quickly get a rough estimate (i.e. critically slow vs. slow vs. normal vs. fast vs. critically fast), 6 seconds is probably sufficient, as long as the rhythm is regular. (though I don't know of a device in the US that regularly records cardiac rhythms in increments of 6 seconds.)
Dr. Strong medicine, is the qRs axis location related to the cardiac muscle masses of the left and right ventricle? For instance, if a person has more right ventricle muscle mass, like a baby, so the aRs axis shifts to the right (more towards the RAD area). If a person who has more left ventricle muscle mass, such as an elderly male overweight patients with hypertension, or even possibly left ventricle hypertrophy, then the aRs axis shifts towards the LAD area. I hope I got it right.
I don't understand why the axis was clockwise for some leads to determining the degrees of deviation, and for some, it was anti-clockwise for some leads, on the LL axis definition. During the eqiuphasic approach around 19:56 of the video. Can you please clarify this part, thank you.
In the Determining Axis-Equiphasic Method, in the first example we count the 90degrees away lead clockwise, in the other example we do anticlockwise. I can't understand how to decide the determining factor for clockwise or antuclockwise counting?
Thanks for the resources that you made available worldwide, I think there is problem with the final(4th) example of the "Determining Axis - Quadrant Approach" slide, and I think it's with EKG itself, coz even though you determined normal axis, lead I is about +1.6 and aVF is about -1.7 so the axis should be more negative than 45° about -50° ??? Am I right??
There are several approaches for determining a precise QRS axis, but one cannot use a comparison of the absolute amplitude of the QRS complex in different leads. It's my understanding that at least some ECG machines measure the net area of the curve - but this is impractical to do manually. One might also be able to use the R:S ratio in each lead, but in this particular example, the S in I and R in aVF are so small as to again be impossible to accurately measure manually. Determining the QRS axis is one of 2 things (in addition to the rate determination) that the computer does more accurately than an experienced clinician.
@@StrongMed Thank you so much for your quick and clear answer, I also wanted to say thanks for all that you do, you probably have no idea how your videos impacting people's lives in many different ways, worldwide. Also wanted to ask you to update & improve the Playlists in channel coz I assume it'll take relatively short time but it'll be really helpful for your new followers.
hello eric, what's the difference between LAD and RAD clinicaly speaking? what am i trying to say is if i determine LAD or RAD i can make the same diagnosis?
At 18:34 you say that lead III is what lies 90 degrees away from aVR, why not choose aVL instead? Both are 90 degrees away, and in the preceeding example you went clockwise, not anti-clockwise?
Chiranthie Karunaratna aVL is actually 120 degrees away from aVR. Each lead has only 1 other lead to which it is perpendicular. (i.e. there are 3 pairs of perpendicular leads: I/aVF, II/aVL, III,aVR)
Thanks for the video, I have a simple question. When is determining the specific degree of axis deviation important? If I can figure out I have a rightward axis between 90 and 180 degrees, what other use is there in getting more specific and calculating an axis of 164 degrees, for example? How would I apply this finding clinically? Or is truly enough just to know when an axis is left vs right vs normal?
This is a great question that has been the topic of more than one discussion between myself and cardiologists here at Stanford. In my experience with adult patients, calculating a precise axis has literally never been a useful thing with a single patient. I've spoken to electrophysiologists (cardiologists who specialize in treating disorders of the heart's conduction system - i.e. ECG experts) here who completely agree, and think it's unnecessary to teach students this skill (including the so-called "equiphasic approach") - instead stating that it's sufficient to classify the axis as normal vs. left vs. right vs. right superior (or "extreme axis"). However, other cardiologists disagree - one example cited is that calculating precise axis may be helpful in identifying congenital heart disease (to which I would respond that diagnosing congenital heart disease via ECG is a skill needed by
Hi Eric. I've got an ECG with a positive lead I and a negative AVF which puts the axis in ?LAD. I then looked at lead II which happened to be equiphasic - would that make the axis normal or LAD?
hiimcanadian Yes, the axis is then at -30 degrees (i.e. same direction as aVL). This is just at the border of normal vs. LAD. If the ECG is in an adult or older teenager, and there is no other evidence of heart disease on the ECG, I wouldn't worry about it at all. But if there is additional evidence of LVH (i.e. large amplitude of QRS complexes in I, aVL, V5, and V6; ST depressins and T wave inversions in I, aVL, V5, and V6), it might be consistent with that diagnosis instead. And if an ECG had an axis of -30 in a young child, that would be abnormal and would warrant a little more thought as to potential causes.
Dear Dr Strong: thanks for your fantastic videos, i have a question in your Equiphasic Approach, the point number 2: to determine which lead lies 90 degree away from the most equiphasic lead, my question is how do i know if the 90 degree away from the equiphasic lead should go clockwise direction or anticlockwise direction ? be cause if i go wrong direction i will make me to get a wrong lead to read in step 3/
How do you decide which way to go 90 degrees. sometimes you go clockwise and sometimes you go counterclockwise. you also alternated between going positive 90 degrees and negative 90 degrees?
Each lead has only one other lead that's 90 degrees away from it (I aVF; II aVL; III aVR), so from the equiphasic leads, there is only one choice which way to go. Half the time it will be clockwise, half the time it will be counterclockwise.
May I ask what is the difference between sinus arrest and sinus block? I would feel sinus arrest no P wave because SA node no fire, where as sinus block has P wave but no QRS, because SA fire but blocked. but when I look the picture different that what I thought. sometimes I see both of them has P
Pathophysiologically, in sinus arrest, the sinus node itself is no longer working. Whereas in sinus block, the sinus node itself works, but the myocardial tissue immediately surrounding the sinus node is damaged, preventing signals from passing through normally. This can be differentiated during an electrophysiology study in which an electrode is introduced to the right atrium and literally inserted into the sinus node to record its activity directly. On EKG, in sinus arrest, there are simply no P waves at all. In sinus block, there may or may not be P waves, depending on the type/severity of sinus block. Sinus block has 3 subtypes, just like AV block: Type 1 sinus block - All sinus impulses generate P waves. There is a delay between sinus impulse and P wave, but since the sinus impulse is not visible on the EKG, this condition is indistinguishable from normal on EKG. Type 2 sinus block - Some but not all sinus impulses generate P waves. This can look like extreme sinus arrhythmia, but if examined very carefully and over longer periods than just a conventional 10 second EKG, sometimes patterns in the irregularity of P waves can be discerned that suggest the diagnosis. Type 3 sinus block - No sinus impulses generate P waves. This is indistinguishable on EKG from sinus arrest. I have a whole video that discusses sinus node dysfunction, including sinus node exit block, here: th-cam.com/video/H6yTQm2h8dc/w-d-xo.html
Different teachers in TH-cam have different teachings. The other video I watched was, they use L1 and L111 to determine the axis quadrant. My EKG book by Karen Ellis uses L1 and avF to determine the axis quadrant. I get confuse here.
Based on the rules of vector addition, only 2 of the frontal leads (I, II, III, aVR, aVL, aVF) are necessary in order to calculate the other 4. So one could theoretically use any 2 leads to determine the QRS axis. However, it is extremely cumbersome to do this using any combination other than the one presented in this video (Looking at I and aVF, followed by II if necessary). My guess is that most of those other references are using a different range of normal than -30 to +90, which may not be strictly speaking wrong. As discussed in the video, there is not consensus on the range of normal, but in my experience, -30 to +90 comes the closest - excluding pediatrics. However, I just took a quick look at Ellis' book online. In it, she states that in a normal EKG, leads I, II, III, aVF, and aVL should all have positive QRS complexes. This is factually wrong - as in not debatable. In a patient with a QRS axis of +15 (considered normal by all references I've ever seen), the QRS complex will be predominantly negative in III. So based just on that inaccuracy alone, I might steer clear of that particular text.
Very very good.... Big fan of your teaching methods sir! One question... Many books still continue you to mention the normal range of the heart rate as 60-100? As undergraduate student... In vivas if we say 50-90... There is no way we can justify our answer...cos all books say 60-100
Suraj Utmani I completely understand - this is a mild point of contention at my own med school. However, I feel quite confident (based on literature and the crazy history as to why 60-100 is considered the "normal rate" to begin with) that literally, every ECG book in print is wrong about this. I'll be posting a new video in the next couple of weeks focusing on just this issue.
+Suraj Utmani I posted a new video today specifically on the topic of the normal heart rate range, which I hope will provide ample justification for using 50-90.
Had a cold. I would have liked to defer recording it until later, but I also wanted to post it before a class I was teaching on some intermediate EKG topics, in case students wanted to review it beforehand. I had considered replacing the audio without completely reposting the video again, but it would be too painful to get all of the timings right. Glad you found it helpful!
I appreciate that most references list the direction of aVR as -150, but that's likely only to provide a sense of symmetry. -150 is geometrically identical to +210.
If you are talking about step 2 of the equiphasic approach (@16:20), you go in whatever direction brings you to the same direction/angle as another defined lead. Since the 6 leads consist of 3 perpendicular pairs (e.g. I/aVF, II/aVL, III/aVR), there will always be 1 lead and 1 lead only that is 90 degrees away. Sometimes that will be in a clockwise direction, and sometimes in a counterclockwise direction.
They are actually the same. If one travels 150 degrees around counterclockwise, and also 210 degrees clockwise, you'll be at the same point. You can describe it either as -150 or +210: Both are equally correct.
Couldn't understand it the first time....Watched it two or three times more..... and now it makes a sense .....Very well explained....
Even after so many years I always put u first each time i need help for EKG
Very good video! I am a patient with a misdiagnosed EKG that stopped an operation because it showed that I had a silent heart attack sometime in the past. I had to go to a cardiologist for a second opinion so that I could proceed with the surgery. The cardiologist compared the two EKGs and explained that the operator of the first EKG had positioned one of the leads incorrectly. Good news for me!
I was very concerned that in today’s modern medicine this type of error not only cost my insurance company more money but worried me for more than a week.
Your videos where very instructive, I am an electrical engineer and I understood the basics of the EKG and was able to understand the conclusion of the cardiologist.
Thank you!
first time in 3 years of med school that i've even begun to grasp what axis is .... excellent video series
This is by far the best ECG Axis video on TH-cam. The Physician is obviously talented.
Thanks dr strong...the most selfless teacher
This made my medical school's cardiopulmonary exam block so much easier and... (gasp) dare I say... fun! Thank you for posting these EKG videos.
Amazing! Thank you so much for making these. The graphics are perfect and precise, and your method of teaching is deliberate and clear. I'm a first year IM resident and I have been struggling with EKG's. I feel like my medical school really did a poor job at teaching how to interpret EKG's. But your videos are bringing me up to speed in no time! Thank you so much, and keep them coming!
Where does the number 300 come to calculate the rate? Can you explain please? Thank you.
@@docgirl13 I hope you have got your answer by now. but i will like to reply to this comment for those who are reading this to find answer.
the ECG machine travel at a rate of 5 big boxes in 1 sec , so it will travel 60sec x 5 big boxes =300 big boxes in one minute.
your heart beat relation to big boxes can be written as = 1 heart beat / x no. of big boxes ( where 'x' represent the no of big boxes the machine travel during the duration of 1 heart beat )
so if you multiply both you get heart beat in relation to 1 min i.e 300/ x no of big boxes
hope this help
@@gautamphulara6866 Thank you very much.
I have gone through 3 books and multiple materials online to understand axis deviation. This is the only one that really made me get it! Thank you!
Amazing. I have watched a huge amount of videos explaining this concept and this is by far my favourite. Thank you!
Sir Thanks a lot. U r the most efficient teacher I have ever seen. Thanks for putting ur valuable time and knowledge for us. And I will remember for u ever 🙏 thanks and love from india
thank you SO much! hands down the BEST EKG series on TH-cam!
One of the best Explanations of ECG thank you so much Doctor!
Best ekg lecture with so much thought and effort put in!
once again, I want to say THANKS for this perfect lecture!
Thank you so much for these videos Dr. Strong - they're are getting me, and many in my class, through learning EKGs at Mizzou!
Such a good video, really helped me understand QRS axis as I was having difficulty understanding it. Thanks again man! :D
Very simple presentation with great understanding; Thank you so much; I got lot from the lecture.
When discussing the equiphasic approach to determining the QRS axis, the "2nd lead" mentioned in Step 3 is a little bit of a confusing term; could use the term "orthogonal lead to equiphasic lead" @17:59
Best explanation I have found of determining MEA. Thank you!
Nice explanation of the quadrant approach; for the equidiphasic approach I enjoyed the explanation on 12ems; a video tutorial showing the actual steps would have been nicer, words/ pics are for some kinda difficult here, esp. if multiple arrows are used; and for 17:06 (I got asked) "3. If the qrs [...]" --> in other words:
If one uses a ruler and puts it on a 90° degree angle in resp. to the lead where you have been observing the equi(di)phasic wave, you do not know, via which direction you are supposed to follow the ruler, i.e. you do not know if you need to look on the top of the hexaxial system or check the bottom side; to know this, you check the qrs complex on the ECG paper of the second lead (in fact it is the lead that is kinda covered by your ruler); if the qrs of this second lead is positive, then you need to check where the positive pole of the very same second lead (ruler) is - to get the location of the positive/ negative pole of a lead just check the picture of the hexaxial system on e.g. wiki, it's denoted there with a small arrow pointing upwards (positive pole) or a small arrow pointing downwards (negative pole) - and then, since we were looking for the positive pole, check the degrees written next to the positive pole; et voila that's it (+-15°).
Thank you, Dr Strong! The entire EKG series is amazing.
Greatest teacher on youtube. Thank you again, sir.
This series of videos are truly magnificent.
Thank you
Thank you very much for all your lecture videos. They are really helpful to medicine students.
Very instructive video. My only objection is that the method you propose of calculating the numerical axis is a bit confusing, if one is not overly familiar with all the axes.
I think a more easy and simple way is to look for the perpendicular axis to the isoelectric lead, and then go to the two leads at the two ends of this perpendicular. The lead with the the most positive wave is the one which defines the axis.
Many thanks for your videos.
Very simple and clear presentation
Hey all, I've got 2 questions specifically regarding axis determination and possible left axis deviation. For context I am a final year med student. Greatly appreciate any insights, thanks!
1) During med school, we had a number of lectures and tutorials regarding ECG interpretation. Here, two separate consultant cardiologists recommended to me to primarily use lead I and lead II to determine axis, and skip using lead aVF entirely, although I was aware that some resources recommended using lead I and lead aVF. From this video, I now understand that specifically comparing lead I + II vs lead I + aVF and noting whether both are positive allows us to determine between -30 to 0 deg vs 0 to 90 deg. So my question is, given this, is there any particular reason why different resources suggest using different leads? Especially given that most people in the population would have an axis of between +90 to +15 as mentioned earlier in the video. Thus to me it actually makes more sense to use the approach outlined in this video, starting off with lead I + aVF and then moving to lead I + II.
2) In the example shown at 16:06, lead I + aVF suggests possible LAD, but checking lead I + II confirms normal axis, suggesting an axis of between -30 to 0 degrees. My question is, if this is the case, why would the amplitude in lead aVF be so big? Given that the vector of electrical depolarisation is fairly perpendicular to aVF? Wouldn't it make more sense that the amplitude be smaller than it is shown, and probably closer to being equiphasic?
Thanks :)
Very practical and useful video .Thanks
This is an awesome video! Thank you for posting and sharing your knowledge.
Awesome stuff Doc, better than any book !
Excellent simple explanation. Thank you for the great video.
Thank you so much doctor for explainig very well. I have a simple question in 19:29, Why not directly see what lies 90 degrees away from Lead II, why we use aVF?
That was smoothly explained and easily digested .. Really thank you so much
Thank you for this clear, concise explanation!
Dr Eric,
You said 'move 90 degrees from the equiphasic lead'. Do you move clockwise or anti clockwise? And why a particular direction
Divya, with each of the 6 frontal leads, there is only 1 other lead that is 90 degrees away from it: I and aVF are a perpendicular pair, II and aVL are a perpendicular pair, and III and aVR are a perpendicular pair. Once you've identified the equiphasic lead, you simply look at the one lead that is 90 degrees away, irrespective of whether it is clockwise or counterclockwise.
For example, if I is the equiphasic lead, you should look at aVF, whereas if aVF is the equiphasic lead, you should look at I.
For a graphical representation of what I'm describing, you can look at my video on EKG leads at the picture around 10:15.
Thanks Dr Eric!:) That makes sense lol
***** Thank you for responding :)! according to Dr Eric's response to this post-he's saying it shouldnt matter and I just go to the perpendicular lead? as in avL if lead II is equiphasic and lead I if avF is equiphasic? But youre saying move to the adjacent lead thats positive?
***** Sorry, I didn't mean to imply that Play With Giles' method is not as equally valid as the one I use in the video (which it is!).
Physician Assistant student here. Thank you for posting this!
Thank you Doctor Strong, wonderful.
Thank you very much! Helps a lot! You´re amazing for charing this with us.
Good evening doctor and an amazing teacher, in the third example for determining axis at 20:18 if we use the vector method and actually put values in tan inverse (aVF/lead I), the answer comes close to around -45 degrees. While your method seems absolutely correct, can you please help point out the mistake in my method?
Love this thank you thank you! I have a huge final in 3 days and this video is totally helping me!
thank you very much your videos has been a great help to me .. i wish if i knew about them earlier at my college years where i struggled my way thru ECG .. thank u again :)
14:23
as for the quadrant approach
what if Lead I is positive and Lead aVF is equiphasic ?
thanks for the videos and the time you dedicate for teaching!
Thank you so much Dr. Strong
Thank you, I definitely have a much better understanding❤
Thank you so much Eric for these videos!
I finally understand this. Thank you!
Thank you so much for making it simple 🌼🙏
thank you so much! your videos are really concise and helpful!
how do you know whether to rotate clockwise or counterclockwise when determining which lead lies 90 degrees or 190 degrees away?
I have the same question :(
thank you so much sir! it's very helpful! you've saved so many lives, for sure!
Great video, thank you very much!
Yay finally easy to understand EKG vid I'm a biochemist n EMT I in med reserve corp I'll share with my EMTs:)
5:02 Is there anything that could be missed by using a 6 second rule on a strip to determine bpm? such as 7beats over 6 a second strip x 10 = 70bpm?
The shorter duration of the sample, the less accurate it will be - particularly for slower rhythms. But if the goal is only to quickly get a rough estimate (i.e. critically slow vs. slow vs. normal vs. fast vs. critically fast), 6 seconds is probably sufficient, as long as the rhythm is regular. (though I don't know of a device in the US that regularly records cardiac rhythms in increments of 6 seconds.)
Dr. Strong medicine, is the qRs axis location related to the cardiac muscle masses of the left and right ventricle? For instance, if a person has more right ventricle muscle mass, like a baby, so the aRs axis shifts to the right (more towards the RAD area). If a person who has more left ventricle muscle mass, such as an elderly male overweight patients with hypertension, or even possibly left ventricle hypertrophy, then the aRs axis shifts towards the LAD area. I hope I got it right.
Javier, thanks for the advertising. I'm not actually on Twitter myself. Maybe at some point in the future.
I don't understand why the axis was clockwise for some leads to determining the degrees of deviation, and for some, it was anti-clockwise for some leads, on the LL axis definition. During the eqiuphasic approach around 19:56 of the video. Can you please clarify this part, thank you.
Quadrant approach 13:30
Excellent! Keep up the good work! This was extremely helpful!
Omg thank you so much for these videos!!! They are great!!
Finally, that's a very useful and practical explanation. Thank you so much for uploading this, you've got a new subscriber now!
Doctor, at 19:38 you said that aVF is negative,is this an error? Please explain.
The QRS complex in lead aVF in the on-screen example is predominantly negative compared to the EKG baseline (i.e. oriented downward).
@@StrongMed Ah i see I was focused on the wrong image there haha. Thank you doctor!
very nice video Sir
In the Determining Axis-Equiphasic Method, in the first example we count the 90degrees away lead clockwise, in the other example we do anticlockwise. I can't understand how to decide the determining factor for clockwise or antuclockwise counting?
Thanks for the resources that you made available worldwide,
I think there is problem with the final(4th) example of the "Determining Axis - Quadrant Approach" slide, and I think it's with EKG itself, coz even though you determined normal axis, lead I is about +1.6 and aVF is about -1.7 so the axis should be more negative than 45° about -50° ??? Am I right??
There are several approaches for determining a precise QRS axis, but one cannot use a comparison of the absolute amplitude of the QRS complex in different leads. It's my understanding that at least some ECG machines measure the net area of the curve - but this is impractical to do manually. One might also be able to use the R:S ratio in each lead, but in this particular example, the S in I and R in aVF are so small as to again be impossible to accurately measure manually. Determining the QRS axis is one of 2 things (in addition to the rate determination) that the computer does more accurately than an experienced clinician.
@@StrongMed Thank you so much for your quick and clear answer, I also wanted to say thanks for all that you do, you probably have no idea how your videos impacting people's lives in many different ways, worldwide.
Also wanted to ask you to update & improve the Playlists in channel coz I assume it'll take relatively short time but it'll be really helpful for your new followers.
Thanks for the kind words and suggestion. Can you be more specific about what you think should be changed with the playlists?
Thank you for the video.
My question is, can we use 10 second rule for the regular rhythms also?
Yes you can!
Sir, while determining axis following equiphasic approach,how do we know whether to move clockwise or anticlockwise from lead 1
hello eric, what's the difference between LAD and RAD clinicaly speaking? what am i trying to say is if i determine LAD or RAD i can make the same diagnosis?
At 18:34 you say that lead III is what lies 90 degrees away from aVR, why not choose aVL instead? Both are 90 degrees away, and in the preceeding example you went clockwise, not anti-clockwise?
Chiranthie Karunaratna aVL is actually 120 degrees away from aVR. Each lead has only 1 other lead to which it is perpendicular. (i.e. there are 3 pairs of perpendicular leads: I/aVF, II/aVL, III,aVR)
Thanks doc!
Thanks for the video, I have a simple question. When is determining the specific degree of axis deviation important? If I can figure out I have a rightward axis between 90 and 180 degrees, what other use is there in getting more specific and calculating an axis of 164 degrees, for example? How would I apply this finding clinically? Or is truly enough just to know when an axis is left vs right vs normal?
This is a great question that has been the topic of more than one discussion between myself and cardiologists here at Stanford. In my experience with adult patients, calculating a precise axis has literally never been a useful thing with a single patient. I've spoken to electrophysiologists (cardiologists who specialize in treating disorders of the heart's conduction system - i.e. ECG experts) here who completely agree, and think it's unnecessary to teach students this skill (including the so-called "equiphasic approach") - instead stating that it's sufficient to classify the axis as normal vs. left vs. right vs. right superior (or "extreme axis"). However, other cardiologists disagree - one example cited is that calculating precise axis may be helpful in identifying congenital heart disease (to which I would respond that diagnosing congenital heart disease via ECG is a skill needed by
Hi Eric. I've got an ECG with a positive lead I and a negative AVF which puts the axis in ?LAD. I then looked at lead II which happened to be equiphasic - would that make the axis normal or LAD?
Lead II hence axis is 90 degrees away from lead II - would that be... aVL?
hiimcanadian Yes, the axis is then at -30 degrees (i.e. same direction as aVL). This is just at the border of normal vs. LAD. If the ECG is in an adult or older teenager, and there is no other evidence of heart disease on the ECG, I wouldn't worry about it at all. But if there is additional evidence of LVH (i.e. large amplitude of QRS complexes in I, aVL, V5, and V6; ST depressins and T wave inversions in I, aVL, V5, and V6), it might be consistent with that diagnosis instead. And if an ECG had an axis of -30 in a young child, that would be abnormal and would warrant a little more thought as to potential causes.
Does it matter which lead u r using to calculate the Rate? You used V1..does it matter if I use lead II? Please answer..thank u in advance
Dear Dr Strong: thanks for your fantastic videos, i have a question in your Equiphasic Approach, the point number 2: to determine which lead lies 90 degree away from the most equiphasic lead, my question is how do i know if the 90 degree away from the equiphasic lead should go clockwise direction or anticlockwise direction ? be cause if i go wrong direction i will make me to get a wrong lead to read in step 3/
I think you can go either way but only 1 direction will give you the precise degrees of your 2nd lead.
👍👍👍😀
In avf positive and lead1 negative then again we have a qn. That it can be b/w 90-120 degrees
I have also heard the equiphasic QRS complex be called biphasic
That was really helpful! Thank you!!
Thank you very much.
U are the best 😍😍😍😍😍😍😍😍😍😍😍😍😍
How do you decide which way to go 90 degrees. sometimes you go clockwise and sometimes you go counterclockwise. you also alternated between going positive 90 degrees and negative 90 degrees?
Each lead has only one other lead that's 90 degrees away from it (I aVF; II aVL; III aVR), so from the equiphasic leads, there is only one choice which way to go. Half the time it will be clockwise, half the time it will be counterclockwise.
@@StrongMed thank you!!!!
What does this do for me in prehospital?
May I ask what is the difference between sinus arrest and sinus block? I would feel sinus arrest no P wave because SA node no fire, where as sinus block has P wave but no QRS, because SA fire but blocked. but when I look the picture different that what I thought. sometimes I see both of them has P
Pathophysiologically, in sinus arrest, the sinus node itself is no longer working. Whereas in sinus block, the sinus node itself works, but the myocardial tissue immediately surrounding the sinus node is damaged, preventing signals from passing through normally. This can be differentiated during an electrophysiology study in which an electrode is introduced to the right atrium and literally inserted into the sinus node to record its activity directly.
On EKG, in sinus arrest, there are simply no P waves at all. In sinus block, there may or may not be P waves, depending on the type/severity of sinus block. Sinus block has 3 subtypes, just like AV block:
Type 1 sinus block - All sinus impulses generate P waves. There is a delay between sinus impulse and P wave, but since the sinus impulse is not visible on the EKG, this condition is indistinguishable from normal on EKG.
Type 2 sinus block - Some but not all sinus impulses generate P waves. This can look like extreme sinus arrhythmia, but if examined very carefully and over longer periods than just a conventional 10 second EKG, sometimes patterns in the irregularity of P waves can be discerned that suggest the diagnosis.
Type 3 sinus block - No sinus impulses generate P waves. This is indistinguishable on EKG from sinus arrest.
I have a whole video that discusses sinus node dysfunction, including sinus node exit block, here: th-cam.com/video/H6yTQm2h8dc/w-d-xo.html
@@StrongMed I really appreciated your explanation Professor strong😭. very clear I understand now.
The equiphasic approach confuses me . Isn’t the direction mentioned anti-clockwise ? Am I missing a point ? Kindly help
Different teachers in TH-cam have different teachings. The other video I watched was, they use L1 and L111 to determine the axis quadrant. My EKG book by Karen Ellis uses L1 and avF to determine the axis quadrant. I get confuse here.
Based on the rules of vector addition, only 2 of the frontal leads (I, II, III, aVR, aVL, aVF) are necessary in order to calculate the other 4. So one could theoretically use any 2 leads to determine the QRS axis. However, it is extremely cumbersome to do this using any combination other than the one presented in this video (Looking at I and aVF, followed by II if necessary). My guess is that most of those other references are using a different range of normal than -30 to +90, which may not be strictly speaking wrong. As discussed in the video, there is not consensus on the range of normal, but in my experience, -30 to +90 comes the closest - excluding pediatrics.
However, I just took a quick look at Ellis' book online. In it, she states that in a normal EKG, leads I, II, III, aVF, and aVL should all have positive QRS complexes. This is factually wrong - as in not debatable. In a patient with a QRS axis of +15 (considered normal by all references I've ever seen), the QRS complex will be predominantly negative in III. So based just on that inaccuracy alone, I might steer clear of that particular text.
Very very good.... Big fan of your teaching methods sir! One question... Many books still continue you to mention the normal range of the heart rate as 60-100? As undergraduate student... In vivas if we say 50-90... There is no way we can justify our answer...cos all books say 60-100
Suraj Utmani I completely understand - this is a mild point of contention at my own med school. However, I feel quite confident (based on literature and the crazy history as to why 60-100 is considered the "normal rate" to begin with) that literally, every ECG book in print is wrong about this. I'll be posting a new video in the next couple of weeks focusing on just this issue.
+Suraj Utmani I posted a new video today specifically on the topic of the normal heart rate range, which I hope will provide ample justification for using 50-90.
Is it just me... or do you sound sad in this video compared to the others? :( ... Thanks for all your help! Much appreciated!
Had a cold. I would have liked to defer recording it until later, but I also wanted to post it before a class I was teaching on some intermediate EKG topics, in case students wanted to review it beforehand. I had considered replacing the audio without completely reposting the video again, but it would be too painful to get all of the timings right. Glad you found it helpful!
awesome!!!! can you upload video on x-rays also.
You are in luck! I'm working on some chest X-ray videos right now. Will post some next week, and some more after Jan 1.
Thank you sir.
what is the actual significance of axis like if ECG shows left axis deviation what it could be the possible problem with heart?
I talk about it in another video here (specific time stamp embedded in link): th-cam.com/video/ENyBhCJ2llY/w-d-xo.html#t=12m19s
thanks a lot! well explained and helped me so much. gracias :D
very helpful, thank you
If lead 1 is equiphasic how to determine axis ?
Bruh what's the music at the beginning it slaps
It's cool I figured it out. If anyone else is wondering it's "Suite No 1. in F Major for the Hornpipe" by Georg Friedrich Händel
aVR is not +210°. please repeat the heart axis.
it is -150° !
I appreciate that most references list the direction of aVR as -150, but that's likely only to provide a sense of symmetry. -150 is geometrically identical to +210.
Do I go 90 degrees clockwise or anticlockwise !!!
Thank you
If you are talking about step 2 of the equiphasic approach (@16:20), you go in whatever direction brings you to the same direction/angle as another defined lead. Since the 6 leads consist of 3 perpendicular pairs (e.g. I/aVF, II/aVL, III/aVR), there will always be 1 lead and 1 lead only that is 90 degrees away. Sometimes that will be in a clockwise direction, and sometimes in a counterclockwise direction.
Crikey! You wouldn't want to get that wrong though would you? It would mean the difference between a RAD and a LAD or a normal axis diagnosis!
@@StrongMed can u explain why this works? What does equiphasic mean physiologically?
the sound of this video is very low ,even with sound box cant hear properly
What about rt axis deviation?
that was sooooooooo helpful
harrisons now says the axis is -30 to 110 , how accurate is it 7 yrs later ?
Though there is not universal agreement, the closest to a consensus is still -30 to +90.
Thank you very very much sir :D :)))))
amazing
Hello. Isnt AVR = -150 degress and NOT +210 degrees???
They are actually the same. If one travels 150 degrees around counterclockwise, and also 210 degrees clockwise, you'll be at the same point. You can describe it either as -150 or +210: Both are equally correct.
wonderful !!!