Editing Electrocardiography (section)

===Augmented limb leads===
Leads aVR, aVL, and aVF are the ''augmented limb leads''. They are derived from the same three electrodes as leads I, II, and III, but they use Goldberger's central terminal as their negative pole. Goldberger's central terminal is a combination of inputs from two limb electrodes, with a different combination for each augmented lead. It is referred to immediately below as "the negative pole".
* Lead ''augmented vector right'' (aVR) has the positive electrode on the right arm. The negative pole is a combination of the left arm electrode and the left leg electrode: <math display="block">
aVR = RA - \frac{1}{2} (LA + LL) = \frac 32 (RA - V_W)
</math>
* Lead ''augmented vector left'' (aVL) has the positive electrode on the left arm. The negative pole is a combination of the right arm electrode and the left leg electrode: <math display="block">
aVL = LA - \frac{1}{2} (RA + LL) = \frac 32 (LA - V_W)
</math>
* Lead ''augmented vector foot'' (aVF) has the positive electrode on the left leg. The negative pole is a combination of the right arm electrode and the left arm electrode: <math display="block">
aVF = LL - \frac{1}{2} (RA + LA) = \frac 32 (LL - V_W)
</math>

Together with leads I, II, and III, augmented limb leads aVR, aVL, and aVF form the basis of the [[hexaxial reference system]], which is used to calculate the heart's electrical axis in the frontal plane.<ref name="Meek 415–418">{{cite journal |last1=Meek |first1=S. |title=ABC of clinical electrocardiography: Introduction. I---Leads, rate, rhythm, and cardiac axis |journal=BMJ |date=16 February 2002 |volume=324 |issue=7334 |pages=415–418 |doi=10.1136/bmj.324.7334.415 |pmid=11850377 |pmc=1122339 }}</ref>

Older versions of the nodes (VR, VL, VF) use Wilson's central terminal as the negative pole, but the amplitude is too small for the thick lines of old ECG machines. The Goldberger terminals scale up (augments) the Wilson results by 50%, at the cost of sacrificing physical correctness by not having the same negative pole for all three.<ref>{{cite journal |last1=Madias |first1=JE |title=On recording the unipolar ECG limb leads via the Wilson's vs the Goldberger's terminals: aVR, aVL, and aVF revisited. |journal=Indian Pacing and Electrophysiology Journal |date=2008 |volume=8 |issue=4 |pages=292–297 |pmid=18982138 |pmc=2572021}}</ref>