ECG Leads

[MedStudent219]

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Hey, I'm just a bit confused about how leads work. For example avR, avF and avL are unipolar leads, however according to my textbook, they average out the other limb electrodes to get a negative lead. How does that work? How does it do this? can someone sort of explain it or point me in the right direction? Also this is a really dumb question, but how is something like Lead I have it's positive electrode at 0 degrees? wouldn't the electrode on the patient's left hand mean that it's underneath the heart --> not to the left (in simple terms, how do we know a lead is at a particular angle, when the electrodes are most likely not when compared to the position of the heart)? sorry if this is a really dumb question, if someone could give me some advice I'd really appreciate it. Thank you so much, this forum is amazing!

 

[MedStudent219]

bump

 

[libertyyne]

Look up Najeeb ECG on youtube.

 

[Quantal Reasoning]

Treat the negative leads as a single lead, and by "average" I think it means take the center of the two leads as the "average" space for the negative field.

 

[mybluedog]

The boards and beyond video for EKGs are pretty sweet.

 

[allantois]

Lead I is arbitrarily assigned 0 degrees. Your augmented vector leads are obtained from averaging out other leads (e.g. aVF is obtained from Lead II and III).
Maybe give Dubin's book a quick read.