@@tasieprecious1678 Maybe it's a figure of speech? In the U.S. when we say "split the difference" we mean "cut it in half." So if you calculate both axes, one is 60 and the other is 90, by "splitting the difference" you would settle on 75.
@@TomBouthillet I understand, but the difference between 90 and 60 is 30, then when divided into half, we have 15. Or do you mean addition of both degrees not subtraction?
@@tasieprecious1678 Thanks for the follow-up. I understand the confusion now. The difference between 60 and 90 is 30 but if you "split the difference" between 60 and 90 the answer would be 75. So I think this is semantics. For example, I just prompted Bard (Google's A.I.): "If I asked you to "split the difference" between 60 and 90 what would you say?" and Bard replied, "If you asked me to "split the difference" between 60 and 90, I would say 75. This is because 75 is the average of 60 and 90." I did the same exercise with ChatGPT and it replied, "If you asked me to split the difference between 60 and 90, I would calculate the midpoint between these two numbers. The difference between 90 and 60 is 30, so to find the midpoint, you would add half of that difference (which is 15) to 60. Therefore, the midpoint between 60 and 90 is 75."
Seriously, I watched over 10 Videos about cardiac axis determination. This one is the best so far. It’s simple, organized and full of examples. Thank you doctor. I wish to see a video that tells the physiological explanation behind the different changes in ECG. Especially in electrolyte imbalance.
Sir at 15:00 ....avr is negative so should nt we take -150 as axis rather than plus 30 degrees....i mean what's the significance of the polarity of the perpendicular vector of vector having equiphasic qrs complex?? Shall we always take the positive value ignoring whether the wave is going upward or downward ..?
That’s just a quirk in the hexaxial reference system. Because the positive electrode for aVR is up on the right shoulder, a normal axis moves away from that positive electrode and produces a negative QRS in that lead. Look at the little down arrow next to 30 degrees. That lets you know the QRS should be negative for a value of 30.
It took me a minute to understand, (being a new student learning online) but I finally got it! Best explanation that I FINALLY understand. Thank you so much!!!!
Amazing video. My 13 year old son has - 56 left deviation. Should I be concerned. He wants to join the soccer team. A volunteer group gave him this free ecg.
This is the dilemma with screening young athletes with 12-lead ECGs. Unless there is clear evidence of left ventricular hypertrophy / hypertrophic cardiomyopathy, a long/short QT interval, a Brugada pattern, arrhythmogenic right ventricular dysplasia, Wolff-Parkinson-White pattern (delta waves), or concerning arrhythmias, there is a chance the athlete will not be signed off because “normal” is the hardest diagnosis in medicine. If you’re worried you could see if you can schedule an echocardiogram but insurance may not pay for it. Good luck resolving the issue!
how do these ionic events actually create the familiar ECG trace? Our electrodes are attached to the patient's skin, not to the surface of their cells. How can cardiac electrical activity be measured by external electrodes?
The electrical activity of the heart is generated by the movement of ions across the cell membranes of cardiac muscle cells. When these ions move, they create an electrical field that can be detected by electrodes placed on the skin. The ECG machine amplifies this signal and displays it on a graph. The ECG trace is not a direct representation of the electrical activity of the heart cells. Instead, it is a representation of the net electrical field as it is detected by the electrodes.
Hi Tom Thanks for the video. Really enjoyed it What is the extra tip to know about avR and avL in the hexaxial system with regards to determining the mean QRS axis
on your discussion on extreme right axis deviation, you had me confused, ( time stamp 29.00-29.06). your box red box was highlighting leads II as perpendicular to AVF. can you clarify? thanks
I was illustrating what I call a split axis. Because it wasn't clear whether lead I or lead aVL was the equiphasic lead, I calculated both the perpendicular leads, lead II (-) and lead aVF (-). Those have values of -90 and -120. If you split the difference you get -105. The computer measures the axis at -110. That's not the preferred method for this ECG but it can be done.
Quadrant method and speed method? It’s difficult to know what’s enough for a given individual. I use all three methods all the time and for me that’s best. Do what works for you.
In case of physiological left axis deviation example..at 16:50 We had aVL having positive qrs complex ...still we took -30 degrees instead of plus 150 degrees which was in right inferior quadrant ...i am unable to understand among the two values... Positive and negative ...which one we have to choose ??
I think i have got it...we don't have to see the values to determine the polarity...rather that little arrow ...at aVL -30 degrees the little arrow is pointing upward so it will produce positive deflection....and at aVL +150 the little arrow is pointing downward so it produces negative deflection
In the table with six cases the case "0 to 90" has all three leads positive, but if the axis is between 0 and 30, lead III will be neutral or slightly negative, not positive.
This was INSANE. Thank you so so much for this deep and thorough explanation, I was really lost with other videos and couldn’t grasp it at all but you made everything so understandable with every deviation. Thank you, you’re making me enjoy ECG.
I have a question though, instead of going through difficulty and further complicate in determining the axis with the split method, you could have used the quadrant method but i understand youre only trying to show the difft ways. Ive learned alot in this video:)
So after watching this a couple of times thinking "I got this," a question occurred to me. Using the hexaxial system, you stated that lead II is perpendicular to aVL. Wouldn't leads I or III be the perpendicular leads? Lead II would be parallel. When you ise the 3rd case with aVF as the most equiphasic lead, you use lead I as the perpendicular lead. Why not lead III, like in the aVL example. Or lead II, as this would slso be a perpendicular lead?
Hi, Butch! If you look at the hexaxial reference system, the spokes for lead II and lead aVL are perfectly perpendicular. Same for lead I and lead aVF (which is why you use those leads for the quadrant method). upload.wikimedia.org/wikipedia/commons/5/56/Hexaxial_reference_system.svg
Why did you go to -90 for aVF and not 90 for the example ~29 min? Why did you go to the -aVR (30 degrees) instead of aVR (-150) earlier on in the video?
@@TomBouthillet 29:00. Is it because the QRS is negative in lead aVF that you went to the -90 as opposed to +90? Earlier 14:20, same reasoning? Because QRS is negative in aVR?
@@Flash236926 Yes, that is exactly right. The polarity of the QRS complex determines the value. It corresponds to the little up and down arrows around the hexaxial reference system. Great question!
The positive electrode for lead aVL is the left arm electrode. When a depolarization wavefront moves toward a positive electrode, it creates an upright QRS.
No I think there’s some misunderstanding. I get it’s positive QRS but my question is in the ecg paper it’s showing positive avL so technically the vector should’ve pointed towards positive axis which is 150 in the downwards. But instead of positive you plotted the arrow on -30 in the axis. Why so ?
@@Persephone7770 Why do you say that a positive QRS in lead aVL should result in a positive axis? The positive electrode for lead aVL is in the left superior quadrant.
I really like the hexaxial method. Have you used a vector addition method? That's always my go-to when I'm not 100% sure, or can't remember the other mental tricks - you only need aVF and I. To do it you find the total number of small boxes from both (add up the positive deflection eg. 12, subtract any negative deflection eg. 3 = 12-3=9). Then do the same for aVF (Eg. +5-2=3) then draw a rectangle of with those proportions (9x3). The diagonal of that rectangle is your precise axis, and if you measure carefully you can do as well as the computer, and fairly quickly. But I'm totally stealing your hexaxial method for a quicker, dirtier and still quite precise way.
This video is brilliant. You are brilliant. This finally makes sense to me. Thank you from the bottom of my heart.
My pleasure, Sharon Yang! I’m so glad you got something out of it.
@@TomBouthillet can you explain more about the split axis?
You said that the difference is divided, but what u divided was the total.
@@tasieprecious1678 Maybe it's a figure of speech? In the U.S. when we say "split the difference" we mean "cut it in half." So if you calculate both axes, one is 60 and the other is 90, by "splitting the difference" you would settle on 75.
@@TomBouthillet I understand, but the difference between 90 and 60 is 30, then when divided into half, we have 15.
Or do you mean addition of both degrees not subtraction?
@@tasieprecious1678 Thanks for the follow-up. I understand the confusion now. The difference between 60 and 90 is 30 but if you "split the difference" between 60 and 90 the answer would be 75. So I think this is semantics. For example, I just prompted Bard (Google's A.I.): "If I asked you to "split the difference" between 60 and 90 what would you say?" and Bard replied, "If you asked me to "split the difference" between 60 and 90, I would say 75. This is because 75 is the average of 60 and 90." I did the same exercise with ChatGPT and it replied, "If you asked me to split the difference between 60 and 90, I would calculate the midpoint between these two numbers. The difference between 90 and 60 is 30, so to find the midpoint, you would add half of that difference (which is 15) to 60. Therefore, the midpoint between 60 and 90 is 75."
Thank you so much! You really explained this well! Look forward to watching more videos!
Thank you, Mary! Glad you enjoyed the video.
@@TomBouthillet sir can you see my ecg please
Seriously, I watched over 10 Videos about cardiac axis determination. This one is the best so far. It’s simple, organized and full of examples. Thank you doctor.
I wish to see a video that tells the physiological explanation behind the different changes in ECG. Especially in electrolyte imbalance.
Thank you, Asil H! I do have a hyperkalemia video in the pipeline.
Thank you so much.......may God bless u...amazing lecture...pls start uploading again..
These videos r boon for us
Thank you, Shaikh Zoya!
Sir at 15:00 ....avr is negative so should nt we take -150 as axis rather than plus 30 degrees....i mean what's the significance of the polarity of the perpendicular vector of vector having equiphasic qrs complex??
Shall we always take the positive value ignoring whether the wave is going upward or downward ..?
That’s just a quirk in the hexaxial reference system. Because the positive electrode for aVR is up on the right shoulder, a normal axis moves away from that positive electrode and produces a negative QRS in that lead. Look at the little down arrow next to 30 degrees. That lets you know the QRS should be negative for a value of 30.
It took me a minute to understand, (being a new student learning online) but I finally got it! Best explanation that I FINALLY understand. Thank you so much!!!!
I’m glad to hear it was helpful!
Yes
Best axis determination lesson I saw in YT so far. Thank you sir, GODSPEED.
Thanks, Tero!
Thank you so much! I like that “speed method” diagram where can I find that to print/laminate till its committed to memory?
www.ecgmedicaltraining.com/wp-content/uploads/2016/02/rapid-axis-1024x411.png
Amazing video. My 13 year old son has - 56 left deviation. Should I be concerned. He wants to join the soccer team. A volunteer group gave him this free ecg.
This is the dilemma with screening young athletes with 12-lead ECGs. Unless there is clear evidence of left ventricular hypertrophy / hypertrophic cardiomyopathy, a long/short QT interval, a Brugada pattern, arrhythmogenic right ventricular dysplasia, Wolff-Parkinson-White pattern (delta waves), or concerning arrhythmias, there is a chance the athlete will not be signed off because “normal” is the hardest diagnosis in medicine. If you’re worried you could see if you can schedule an echocardiogram but insurance may not pay for it. Good luck resolving the issue!
Thank you for this clear, concise and visually well-illustrated video!
Thank you so much!
how do these ionic events actually create the familiar ECG trace? Our electrodes are attached to the patient's skin, not to the surface of their cells. How can cardiac electrical activity be measured by external electrodes?
The electrical activity of the heart is generated by the movement of ions across the cell membranes of cardiac muscle cells. When these ions move, they create an electrical field that can be detected by electrodes placed on the skin. The ECG machine amplifies this signal and displays it on a graph. The ECG trace is not a direct representation of the electrical activity of the heart cells. Instead, it is a representation of the net electrical field as it is detected by the electrodes.
Well your patient’s skin, like everyone else, is composed of cells
This video by far is the most useful and understandable one compared to others. I love it and thank you !
I’m glad it was helpful!
Super explanations. It’s going to change how I review axis.
Thank you very much!
Thank you, I really appreciate you for being patient to make this video and for being extremely thorough
❤❤❤.
It’s remarkable that you commend my patience. It’s my pleasure. Thank you for watching.
Wow...I learned so much in less time than in a standard college class lecture! Thanx!
That is great to hear! Awesome compliment.
Best explanation I've come across for axis determination. Great job 👍🏼
Thank you very much!
Hi Tom
Thanks for the video. Really enjoyed it
What is the extra tip to know about avR and avL in the hexaxial system with regards to determining the mean QRS axis
Wonderful! Thanks, olatunji oladipo!
Thanks a lot Tom (🙏🏻from India)
Thank you for watching, Dr. Mukul Kanojia!
Oh! My! Lord!!! This is outstanding!!! So freacking easy to understand!! Thanks so much!
Thank you for the praise!
on your discussion on extreme right axis deviation, you had me confused, ( time stamp 29.00-29.06). your box red box was highlighting leads II as perpendicular to AVF. can you clarify? thanks
I was illustrating what I call a split axis. Because it wasn't clear whether lead I or lead aVL was the equiphasic lead, I calculated both the perpendicular leads, lead II (-) and lead aVF (-). Those have values of -90 and -120. If you split the difference you get -105. The computer measures the axis at -110. That's not the preferred method for this ECG but it can be done.
Question, is it enough to know the first two methods of determining all ECGs axises?
Thank you very much
Quadrant method and speed method? It’s difficult to know what’s enough for a given individual. I use all three methods all the time and for me that’s best. Do what works for you.
Thank you so much it was a great explanation 🤍🤍🤍
My pleasure! Glad you enjoyed it.
In case of physiological left axis deviation example..at 16:50
We had aVL having positive qrs complex ...still we took -30 degrees instead of plus 150 degrees which was in right inferior quadrant ...i am unable to understand among the two values...
Positive and negative ...which one we have to choose ??
I think i have got it...we don't have to see the values to determine the polarity...rather that little arrow ...at aVL -30 degrees the little arrow is pointing upward so it will produce positive deflection....and at aVL +150 the little arrow is pointing downward so it produces negative deflection
Fantastic... The video is way much clearer than my instructor!!
I'm glad you liked it.
Great explanation. Thank you so much
Thank you, Kelvin!
Wow... i learned so much in 30 mins video. now I am pretty confident to measure axis deviation without confusion. Thank you so much
My pleasure Varinder Parmar!
Very much appreciated. 🙏🏾
My pleasure!
Well explained 👍👌
Thank you!
Best explanation you can find of axis determination on you tube 🎉
Thank you so much!
In the table with six cases the case "0 to 90" has all three leads positive, but if the axis is between 0 and 30, lead III will be neutral or slightly negative, not positive.
Yes, that's true. It's not a perfect model.
Super helpful. Made everything much clear. Thank You!
Glad you found it to be useful!
nice
Really amazing thanks doctor
This was INSANE. Thank you so so much for this deep and thorough explanation, I was really lost with other videos and couldn’t grasp it at all but you made everything so understandable with every deviation. Thank you, you’re making me enjoy ECG.
Thank you, X Ktv! Glad you found the lesson to be useful.
Nice explanation and teaching
Thanks very much.
This was sooo good]
Glad you enjoyed it!
This is brilliant. I've already added it to my liked videos list.
Many thanks!
You’re welcome, Sami Lazkani!
What is a normal frontal axis T in degrees?
I have a question though, instead of going through difficulty and further complicate in determining the axis with the split method, you could have used the quadrant method but i understand youre only trying to show the difft ways. Ive learned alot in this video:)
By far THE BEST explanation I have ever heard! Thanks!
Can you explain more about Right and left bundle branch block please
Right Bundle Branch Block: ua-cam.com/video/6exhMIuofR0/v-deo.html
Left Bundle Branch Block: ua-cam.com/video/bp-J6n-MPlU/v-deo.html
Very informative
Thank you!
Thank you so much for teaching axis using a very easy and simple method. This is the first time I am listening to your teaching, and I really love it.
Plz start uploading again...
Strong work! Why was the machine interpretation of 12 lead at 31:10 Prob supraventricular tach and not V-tach?
Good point. Computer algorithms are good at certain things but not rhythm analysis!
wow, amazing ! Thank you
Thank you ,Tom.
You are most welcome.
Fantastic video, thank you!
Thanks, Nathan!
Its amazing really
Best teaching to understand Axis determination so far!
Thank you, XiaT!
Just brilliant ty❤
Thank you for your reply. Point well illustrated.
I didn't understand how to use the star of life
Then draw a horizontal line between lead II and aVL and an X between lead I and aVF and lead III and aVR and remember that pattern.
Good lecture
Many thanks.
Thank you that was so helpful!
I’m glad.
Incredibile!
Thank you
I just realized you donated $5.00! Thank you so much!
Wow! What an awesome video!
Thank you, Paul Rumbaoa!
Thank you so much for helping me to learn so I can help the patients ❤️❤️🙏🙏
Glad to help!
So after watching this a couple of times thinking "I got this," a question occurred to me. Using the hexaxial system, you stated that lead II is perpendicular to aVL. Wouldn't leads I or III be the perpendicular leads? Lead II would be parallel. When you ise the 3rd case with aVF as the most equiphasic lead, you use lead I as the perpendicular lead. Why not lead III, like in the aVL example. Or lead II, as this would slso be a perpendicular lead?
Hi, Butch! If you look at the hexaxial reference system, the spokes for lead II and lead aVL are perfectly perpendicular. Same for lead I and lead aVF (which is why you use those leads for the quadrant method). upload.wikimedia.org/wikipedia/commons/5/56/Hexaxial_reference_system.svg
Interesting question and reply
Best axis lecture yet!
Thank you, Sarah!
an excellent video!! thanks a lot
Can misplacing the electrodes on chest cause any deviation of axis???
Yes, definitely.
AMAZING!!!!!!
Thanks, lana!
Wow, really, this was an amazing explanation. Thank you so much!
Thank you for the positive feedback!
This video was incredibly helpful - thank you!
My pleasure, Chisanga!
This is very useful..very helpful... Thank you so much ...
My pleasure!
Why did you go to -90 for aVF and not 90 for the example ~29 min? Why did you go to the -aVR (30 degrees) instead of aVR (-150) earlier on in the video?
Thanks for the comment, Andrew. May I please have an exact time stamp?
@@TomBouthillet 29:00. Is it because the QRS is negative in lead aVF that you went to the -90 as opposed to +90? Earlier 14:20, same reasoning? Because QRS is negative in aVR?
@@Flash236926 Yes, that is exactly right. The polarity of the QRS complex determines the value. It corresponds to the little up and down arrows around the hexaxial reference system. Great question!
@@TomBouthillet Thank you sir. Making medical school easier.
@@Flash236926 Glad to help.
The first example at 17:06 why is positive avL pointing at negative 30 aVL shouldn’t it be at +150 how come is that left axis deviation
The positive electrode for lead aVL is the left arm electrode. When a depolarization wavefront moves toward a positive electrode, it creates an upright QRS.
No I think there’s some misunderstanding. I get it’s positive QRS but my question is in the ecg paper it’s showing positive avL so technically the vector should’ve pointed towards positive axis which is 150 in the downwards. But instead of positive you plotted the arrow on -30 in the axis. Why so ?
@@Persephone7770 Why do you say that a positive QRS in lead aVL should result in a positive axis? The positive electrode for lead aVL is in the left superior quadrant.
I’m so sorry I got confused with the positive sign and didn’t notice that actually the positive is in superior quadrant
Thank you sir
I really like the hexaxial method. Have you used a vector addition method? That's always my go-to when I'm not 100% sure, or can't remember the other mental tricks - you only need aVF and I. To do it you find the total number of small boxes from both (add up the positive deflection eg. 12, subtract any negative deflection eg. 3 = 12-3=9). Then do the same for aVF (Eg. +5-2=3) then draw a rectangle of with those proportions (9x3). The diagonal of that rectangle is your precise axis, and if you measure carefully you can do as well as the computer, and fairly quickly.
But I'm totally stealing your hexaxial method for a quicker, dirtier and still quite precise way.
Thanks for the tip, SireSquish! I am not familiar with the vector addition method but I will check it out.
Soooo helpful! Thank you!
Thank you for the comment!
Thanks a lot
You are welcome!
What a great video I’ve watched so many videos and read my text book and finally understand this a lot better. Thank you so much.
You’re quite welcome Mr. Ninja.