Erratum: @7:27, I misspoke. I should have said "the voltage as measured by lead I plus the voltage as measured by lead *III* must equal the voltage as measured by lead *II*".

You have in 20 mins clarified years of misconceptions that I have had about these leads. Thanks very much.

How lucky we are to have FREE access to such an incredible teacher's lesson! Sincerely, an MS1

I wanna cry, you’re amazing

Your lecture series is SO helpful! So thankful that I found this. Thanks for creating these videos.

Dear Dr. strong, I found your EKG course extremely helpeful as it made me actually understand the principles behind the processes instead of just memorizing them. You really helped me a lot and I mean this literally: I just wrote my final exam in med school and there was one EKG leads localization question. While reading it, I actually heard your comment from this video in my head :-) thanks for that point on the exam! Please keep up your insigthful and valuable work!

I truly appreciate your ability to explain EKG's so well and in a manner slow enough to really take in the concepts. Thank you!!

Wonderful, no one has explained this so well to me before. You were a terrific help, thank you!

Eric, you're the best! I absolutely appreciate your time and effort for these video's. Thanks

My jaw dropped from around the 12th to 13th minute. You’re a living legend, Professor. This was so clear!!!

This is great! Thanks for saying a lead and an electrode are not the same thing. Whole lecture is great!

This is just great! Thanks for your work!. I will recommend your channel to all med students in Sierra Leone

I am always confused about reading EKG. This is very very helpful. Thanks a million!

Your videos are the most complete, competent and easy to learn. i finally got to fully understand this topic in particular thanks to you. this is definitely the best medicine related channel in youtube. i hope you keep updating it and teaching us :)

Thank God for you

BEST video I HAVE CAME ACROSS!!!!

Phenomenal stuff and great approach! Thank you very much, sir!

Your videos are super helpful! Please keep making educational videos for medical students. Thank you for your great work :)

Honestly, I would hug you if I could! Thank you for this classes!

the spatial relationships between leads explanation was great, ty

you couldn’t explain it any better! thank you sir!

These videos are extremely helpful and easy to understand. Thank you so much

Hey Mr. Strong. Thank you for your videos, Im in my first year as an intern in internal med and find them very useful to refresh my ECG knowledge every now and then. The rhythmologist (a cardiologist) at our hospital said Lead I and II are best for atrial activity, 2nd choice at best would be V1. Best, Dr. R.

Thank you Dr Strong. You are a good teacher. No doubt that Stanford would make excellent doctor ,just example that you are one of clinical teacher,instructor. This is my second or third watch of this video. I am glad that I ran into your lecture series. I have no examination to face, that I might help me learn better :) .

Im a third year med student and I have to say your channel is by far the best on KZfaq for medical education!

You're so gentle and informative 💖💕💖

Thank you sir for i could never understand anything about ekg leads no matter how many videos i viewed but your video cleared most of my concepts. Thank you sir for your efforts. Hope you keep making more videos

thank you very much for the kind work Sir. I hope the ecg lectures also continue even more

Thank you, sir. As usual your videos are very informative and easy to follow

Thank you great lecture...will surely watch more of your videos these will definitele help me in my step 2ck exam

Thankyou soo much for such a clear presentation. Cryatal clear on the orientation of leads

This is probably way more info than I need for my ccma certification, but it’s soooo interesting. Very informative. Now, I gotta go back to my notes and fix that ☺️

Thank you so much for your best video.

I had a hard time learning the ECG (and I am still not done yet) so I thought the following might help some people: 7:36 - instead of trying to understand the formula you can rather prove that it is correct and boost your confidence: 1. Take the qrs complex from lead I and substract the obtained values, e.g. let's say the q wave is -0,5, the r wave is +3 and the s wave is -1,5--> -0,5 + 3 + (-1,5) = +1 2. Take the qrs complex from lead II and substract the obtained values, e.g. let's say the q wave is -0,5, the r wave is +8 and the s wave is -4 --> -0,5 + 8 + (-4) = +3,5 3. Take the qrs complex from lead III and substract the obtained values, e.g. let's say the q wave is 0 the r wave is +4,5 and the s wave is -2,5 --> 0 + 4,5 + (-2,5) = 2,5 Now use the formula I + III = II [or the formula I + (-II) + III= 0 (in my opinion more smexy)] and you can see Einthoven was cool: 1 + 2,5= 3,5 [or: 1 + (-3,5) + 2,5 = 0 ] If you're wondering: You gotta use -II because Einthoven, instead of going clockwise, switched the positions of the electrodes of lead II. www.ems12lead.com/2008/10/04/axis-determination-part-i/ good site btw and got my info there! And the "v" in "avR" etc. stands for "vector", not "voltage" Ah and thanks for the video! Helps a lot! 14:48 - the formulas seem to be difficult but they aren't, see the formulas in the link below rather then in the video and you'll understand soon: ecgwaves.com/wp-content/uploads/2016/08/goldblaw.png To understand them just check your hexaxial system, preferably one with with correct poles, e.g. upload.wikimedia.org/wikipedia/commons/5/56/Hexaxial_reference_system.svg (arrow down means negatve pole, arrow up means positive pole). Then check again the formulas I linked and you'll understand :-) 12:25: The q wave in lead II should be a bit negative, right? It was drawn here to be isoelectric because the septal dep. is nearly perpendicular to lead II, correct? Wouldn't then the major ventricular depol. shown in lead III also be isoelectric rather than showing negative (because again it is nearly perpendicular to lead III)?

Thanks for this wonderful lecture, clear and easy to follow.

Thank you. i really enjoy watching your lectures.i hope you cover different branches in future by the way after i have watch ABG lectures.all of my colleague and consultant like the way i analyze the ABG. Great thanks

Thank you sir , it was a pleasure , we being students cant buy all the coursed , it was so generous of you for making it free

always pleasure to watch your videos sir. Waiting impatiently for the last lecture on antibiotics

Thanku & God bless u for this selfless effort sir ❤

Thank you so much, this is gold

this was great!!! Thank you so much!!!

Thank you, simply thank you!

incredibly helpful thanks so much

that was a perfect lecture!

Thank you for the excellent video...

SUPER DUPER HELPFUL!!! THANK YOU!

This is so helpful! Thanks!

it helped me a lot :) very nice channel, thank you!

this was so useful. Thank you.

As an accelerated program nursing student, thank you!!

That is really helpful, thank you very much

lecture is awesome

I have a test Wednesday so thank you for posting the EKG and lead videos. I wasn't grasping my instructor's lectures and you are a lifesaver.

Teşekkürler, gayet faydalı olmuş.

excellent video .... thank u

Very good video!

Almas, I'm glad you enjoyed it. Thanks so much for the catching my misspeak! (I've added an annotation to correct it)

Best of the best

Great Lecture. The vector addition worked best for me with Einthoven's Law. In degrees it doesn't work out. I was taught how to place ECG leads by a very picky Emergency Room Resident. Most of the time my recordings were good but occasionally the problematic ones were people fidgeting about and women with huge pendulous breasts- until an RN told me to tape the breast out of the way so I could palpate the ribs. I'm a physics geek so I figured out a lot about the electrical stuff on my own so if the ECG didn't look right I would repeat it to double check. That resident became an OBG guy!!!!!

I think the reason these 3 are used in the rhythmal strip is due to V1 being most sensitive to the right side of the heart while V5 to the left isde of the heart ( v5 is chosen over v6 because the latter's magnitude value is affected by the pleural tissue) and ofcourse limb lead2 due to it being the most parallel with normal heart activity.

Can you please teach all my classes!!! You are the best!

The reason that Einthoven's triangle represents voltages in the chest even though the electrodes are on the arms and legs is because the voltage on, for instance, the right arm is the same at every point until it reaches the torso. Essentially the arm can be thought of as a wire connected to the torso, and carries the voltage at the point where it attaches to the torso; same with the legs. Voltages only change when currents are flowing, and current only flows when there is a closed path, taking the path of least resistance. No current generated by the heart flows down an arm and then back up, as that would have more resistance than just returning from where the arm meets the torso. Hence, the legs and arms each are at the same voltage as the point where they connect to the torso in which currents from the heart are flowing. Hope that helps; it's a little difficult to put into words, but if one draws a body and models it as a network of resistors, it becomes apparent that no heart-driven current would go down and then back up an arm or leg, it would just return from the point where the arm or leg connects to the body as that is a lower resistance and shorter path. The whole shebang depends on the fact that the body is a conducting but resistive media, and air is insulating, so all current is confined to the body.

THANK YOU!!!

Thank you so much for the explanations! I wish I had encountered this earlier while studying first year physiology :)

Thank you!

thank you very much!

Helped me lots:)

Hoping to finish off the antibiotics lectures next week...

THANK YOU

Fascinating from an OLDER non-med person (a retired engineer) with a right bundle branch block to learn about placement of leads and what they should show...would love to see an EKG strip of my own...not as a criticism, but for knowledge...would be interested in How the leads are differentiated...

awesome

u r awesome...

thank you teach

Respected Sir, you have provided a crystal clear explanation to all these scary lead vectors.Thanks I want to know when we measure potential difference as measured by lead I do we assume right wrist/hand and left hand have different potentials. I am stuck with the point that both the right wrist and left wrist are at same distance from the heart ,then the potential drop should be same in both the cases as we go down towards the wrists !

The reason why lead V5 is on the 12-lead printout is because that lead is good for monitoring ventricular ischemia. During the case, CRNA's keep their monitors usually on II and V5 to best pick up arrhythmias and ischemia. Amazing lectures! I sent an email to your standford.edu email with my notes of your other lectures. Hopefully, that is your current address.

Dear Dr Eric: thanks for your amazing videos, but I have a question, I can see only 5 out of 15 advanced EKG videos here only, where are the other 10 videos?

Thanks

Damn this is fucking outstanding, even better than DD's book

time to get an EKG, G!

Hello Dr. Strong, when you talk about modern EKGs measuring only leads I and II, does that mean that they only have to attach 2 electrodes in the chest? And how does the accuracy of modern EKGs fare with the 12-lead EKG? I saw a device that you only need to hold and put into your left limb. It's called KardiaMobile and it comes with an app.

Great

Is it sufficient for FMG examination

The interventricular septum is actually depolarised from left to right ,and also in upward direction ,(maintaining left to right) but not in inferior direction(maintaining left to right) as told by you. please clarify.The arrow should be slightly upward, & from left to right.

Hello Dr. Strong, I had a question about the PR Segment. Why is this segment at the same level as the TP segment? During the PR segment, there is a great difference in potential between different poles of the heart since the Atria are fully depolarized but the ventricles are still polarized? Is the EKG actually measuring current? This might make more sense because the AV node allows so little current through it.

❤❤❤

A doubt Which lead reading is shown to us in hospitals beside the positing on the ekg monitor just before he dies and the line goes beep......???

Professor, the Wilson’s central terminal I believe is composed by two limb leads as a negative and one as a positive for example for aVR RA will be positive and the average of LA and LL will be the negative, not as stated in the video at 8:25 that it is composed by the potentials of the 3 limbs.

Hello, Can anybody clarify to me why the first of the two vectors on the heart, the one that represents the depolarization of the IV septum, is directed south-west? Doesn't the septum, on the heart, have the same direction as the left ventricle (south-east)? Thank you so much!! x

Please put numbers for your videos , it is good to know the sequences of videos .

Hi. Great course but you are missing one important part to be lecture 2 or 3: how to approach the ecg paper - what are the X and Y axis ? what does the small and big squares mean time wise and voltage wise ? what is a positive and negative waves, how to sum them up and how they relate to vector deflections? and so on...

Thank you so much Proffesor, we would like to get the ppt if it is Possible

👏🏽👏🏽👏🏽!!!

9:55 things get hectic

Hi Dr. Strong, Thanks for the video! I was wondering if you have a video on normal T-wave morphology for each leads vs "strain" associated t-wave inversions vs bundle branch block t-wave inversions, please? Tall order but thanks!

Hi Eric. There are your 24 videos together in you tube. I want to follow and watch consecutevely. Are they arranged sequentially?

Excellent! very helpful. Just one question: Why at 10:34 the event angle is down and directed to right. What does define the direction and angle of the vectors showed in yellow?. Is the only thing I couldn´t understand. Thanks!

Why avF has both positive deflections?

How is the depolarization of intraventricular septum angled down and to the right? I thought the direction of the intraventricular septum was down and to the left???? Please some one help?

Hello Dr. Strong! For the six limb leads, there's 4 electrode placed on the extremities. I'm wondering whether this statement is true? "Limb leads can be placed on any part of the patient's respective limbs. Just make sure the leads are symmetrical. " Some put the electrode just proximal to the wrist, while others put it anterior to the shoulder. I've seen both kinds in the hospital. Wondering it should alter the voltage or lead axis , and therefore affect the analysis?

@13:52, for interseptum voltage, I plus III should be positive, why II is negative instead?