ECG Level 3 Tutorial: Axis
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Tutorial: Axis
This will teach a basic approach to determining the axis of an ECG.
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Tutorial: Axis Defining the Normal axis
Lessons
42
Times Practiced
1284
Cases Completed
1h 24m
Total Time spent
1m 24s
Average Time
Progress
Accuracy
Efficiency
Accuracy
Efficiency
1 Remember the Vector Remember the Vector
2 Quadrants Quadrants
Current lesson 3 Defining the Normal axis Defining the Normal axis
4 The Isoelectric lead The Isoelectric lead
5 Shading the QRS Shading the QRS
Defining the Normal axis
The normal axis is -30 to +90. We simplified things in the previous lesson when we said that the normal axis was the lower right quadrant which is 0 to +90 degrees. That is not 100% accurate.

There is a very quick way to define the range between -30 and +90. Use leads I and II.

If you are positive in both these leads, look at the "double shaded" purple region:
normal ECG axis

It is from -30 to +90. Thus, we have now defined the normal axis with upgoing QRS in both leads I and II.

Here is an example of a normal axis:
ECG normal axis
Notice that the QRS is mostly upgoing in both leads I and II.

How about this one?
ECG LAD axis

Upgoing in I and downgoing in II. Hmmm. Not normal. Where does it double shade?
ECG axis LAD

It double shades from -30 to -90: in the LAD range.
This is your shortcut for LAD: up in I and down in II


And quickly, let's go over 2 more easy shortcuts:
Down in I and up in aVF defines RAD:
RAD ECG axis


Down in I and down in aVF defines the extreme axis:
extreme RAD ECG axis

** remember that "downgoing QRS in aVF" means the QRS is moving away from the feet ... mostly toward the head. That is why the red shaded region is in the top half in the above image.

And there you have it. 4 axis shortcuts in record time. Note that you have to use 3 leads total: I, II, aVF.

Summary of Axis Shortcuts:
  • normal = upgoing in I and II
  • LAD = upgoing in I and downgoing in II
  • RAD = downgoing in I and upgoing in aVF
  • extreme = downgoing in I and aVF