Lead I

Lead I is made by:
* AVL - AVR ( it is not an actual recording but the signal difference between L and R)
* II - III

So, you take the second storey of the ECG where II and aVL live, and subtract III and avR from that.


What is normal for Lead I:

• If the axis is >60degrees( III, II R waves> I, then the heart is horizontal, and so the septum is in line with "lead" I, so will see small Q's(1 small square and  less then 25%  of the R wave height) in II, III and aVF because the depolarization wave is perpandicular to the lie of the septum.

(correspondingly, if the axis is <60 degrees - III, II R waves

• if you see a high R wave in lead I then there must be either a high R wave in aVL or a deep S in avR. The same goes for leads II and III.