Basics of ECG Leads 5-1 - ECG / EKG Interpretation -- BASIC
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- Опубликовано: 5 ноя 2011
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Dr. Nicholas Tullo, a heart rhythm specialist, presents this lesson for the ECG Academy. This instructional video discusses the basic concept of an ECG "lead," the origin of the limb leads, and the concept of cardiac "vectors" and how they relate to the 12 lead tracing. The content of this video will help viewers to understand how to begin to understand axis and the interpretation of an ECG. For basic, intermediate, and advanced video instruction on interpreting ECGs, visit www.ecgacademy.com/
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Thank you for making this education free and available, you have my respect!
Good question. I plan to cover on my website, ECGAcademy -- the simple answer is that depolarization occurs from endocardium to epicardium, while repolarization occurs from epicardium to endocardium. This reversal of direction explains why the T-wave goes in the same direction as the QRS, despite their being opposite electrical events.
Thank you very very much for this! I was looking for a refresher after 2 years away from medicine, but I think you've taught me more of the fundamentals than they did at med school! Very much appreciated.
Great 👍.
@dogmanbill -- For most of the QRS complex, the electrical signal is changing direction. At times it is traveling from left to right, part of the time it's traveling from base to apex, and other parts it travels from apex to base. The AVERAGE vector (the sum of all the parts) is usually DOWN and TO THE LEFT of the patient, which is why the normal "axis" is between 0 and 90 degrees. I hope that clarifies things.
Wow this made sense to me for the first time!! Thanks a lot :)
Good to know
depolarization occurs from epicardium to endocardium so t wave in the same direction i read that ischemia is the reason but i don't know how
+hassan ali Depolarization occurs from Endo to Epi (inside out)...think about the Perkinje fibers. They are inside the heart. It would make sense that as the electrical impulse leaves the fibers and goes into the myocardium, it would start at the origin (inside) and go outside to the epicardium.
Repolarization however goes epi to endo (outside in)...just the opposite.
With an ischemia, the impulse is just having to go "around" the ischemia so the QRS, ST, and T will have varying appearances because the impulse is not "symmetric" throughout the myocardium.
Can you please explain to me why the t-wave is upright in lead II? I have heard that as repolarisation is a negative wave, and the direction of this negative wave flows predominantly back toward the negative RA electrode, the 2 negatives cancel each other out and become a positive. This doesn't make sense to me. Help!
its because of the thing that the last thing to depolarize is the first thing to repolarize :)
Hi Dr Nicholas Tullo, thanks a lot for the helpful and easy to understand tutorial. If a product is able to perform Ambulatory ECG but only can get Lead I ECG form, would that be helpful clinically? What diagnosis can be given by Lead I ECG (only)? If a doctor is able to monitor a patient's Lead I ECG (single lead) constantly, can he prevent any thing from hapening such as heart attact...etc on a prevention point of view? Thank you.
Hi Dr Nicholas Tullo, thanks. Would you please advice what kind of information and diagnosis can be give by Lead I ECG only? Does it make sense to you if there is a very small and wireless ECG that a person can attach it to his chest, record the Lead I ECG and do his normal activities? Who do you think would benefit from it if they are able to monitor their Lead I ECG?
Lead I can give important information about the heart rhythm, but it's not terribly helpful for diagnosing ischemia or infarction and it's useless to predict if something like a heart attack is going to happen.