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Hartas2 (CardioNetworks ECGpedia).jpgNormal cardiac axis (ECG).png
The cardiac axis is the overall direction in which the heart is electrically activated.


  • Define the term 'cardiac axis'
  • Describe an ECG as having a normal axis by confirming leads I and II are both positive.
  • Draw or label the angle that each limb lead 'looks' at the heart from.
  • Identify the normal axis range on a graph of all limb lead angles.
  • Identify an ECG axis as normal, left, right or extreme based on at least one of the methods including:
    • Thumbs method
    • Quadrant shading
    • 90o to Isoelectric lead
  • List causes of left axis deviation (e.g. Inferior MI, LAFB or Paced rhythm), right axis deviation (LPFB, Lateral MI, RVH or right strain), extreme axis deviation (VT, Electrolyte problems or misplaced ECG electrodes) or indeterminate axis.
  • Describe Einthoven's triangle and the history of his development of the cardiac axis
  • Define the 'Hexaxial reference system' and draw this from memory.
  • Plot the axis using net complex heights of two leads.
    • Use this technique to identify changes in the cardiac axis inside the limits of 'normal'.
  • Calculate the axis for P waves and T waves.
  • Analyse the clinical significance of the cardiac axis in a broad range of patient scenarios.

How to use this page:

  • Explore the sections below by clicking on Process, Review, Apply or Contribute to find a variety of educational exercises. Click again to hide the same content.
  • Read the suggestions for each type of activity.
  • Choose your learning goals using the list of skills on the previous slide.
  • Make this page better by editing it or leaving comments on the talk page.

Medical disclaimer: This page is for educational and informational purposes only and may not be construed as medical advice. The information is not intended to replace medical advice offered by physicians. Please refer to the full text of the Wikiversity medical disclaimer.


Nuvola apps kate.png Process
Active learning exercise:
Wizard Hat Icon.png Can you process some new information and transform it into something different?Nuvola multimedia.png

Help: Learning by connectivism involves remixing information to create new connections and links. Start by choosing materials from the collection above that are most relevant to you. Keep a record of which materials you have accessed (suggested ways of doing this can be found here). Transform the information from one format to another. A traditional example of this learning exercise might be taking a lecture and processing it to make dot point notes, but also consider other formats like diagrams, mind maps, short movies and more. Revise your notes by transforming them again rather than just passively reading them. The theory is that this exercise helps you to engage elements of active learning and learning by teaching to increase the quality of your own learning while also creating something useful for others to learn with if you choose to share it.

Nuvola apps korganizer.png Review
Active learning exercise:
Bombilla amarilla - yellow Edison lamp.svg Can you review your knowledge by trying this quiz?True.svg


Icon Transparent Blue.png What is the cardiac axis?

The overall direction that the heart is electrically activated in.
The height of the tallest QRS complex.
The overall angle that the heart physically rotates with each contraction.
The most central anatomical structure in the heart.


Icon Transparent Blue.png Describe these QRS complexes as positive, negative or isoelectric:

A and D are negative, B and C are positive, E is isoelectric.
A and B are isoelectric, C is negative, D and E are positive.
A is positive, B is negative, C, D and E are isoelectric.
A and D are positive, B and C are negative, E is isoelectric.


Icon Transparent Blue.png True or false? Lead I is a horizontal view of the heart and aVF is a vertical view of the heart.



Icon Transparent Green.png Which ECG leads look in the following directions?

Lead I, aVF, aVR, III, aVL, II
Lead I, aVF, II, aVL, III, aVR
aVF, Lead I, II, aVL, III, aVR
aVF, Lead I, aVR, III, aVL, II


Icon Transparent Green.png Describe the following cardiac axes as normal, left, right or extreme:






Pp interrogation.gif Exercise: Can you copy and complete these diagrams from memory?

Stub doctors.svg Apply
Active learning exercise:
Wikiman MD.png Can you apply this information to these clinical examples?

Icon Transparent Green.png Looking only at leads I and II, which of these ECGs has a normal axis?

Case 1
Lead I and Lead II are both positive. The axis is normal.
Case 2
Takotsubo ECG.JPEG
Lead I is positive but Lead II is negative. The axis is abnormal.
Case 3
Electrocardiogram 12derivations male 23yo Japanese.png
Lead I and Lead II are both positive. The axis is normal.

Icon Transparent Green.png Can you use the thumbs method to describe the axis as normal, left or right axis deviation? (click on an ECG to view it)

Icon Transparent Green.png Can you identify which lead is isoelectric? (click on an ECG to view it)

Icon Transparent Yellow.png Can you describe the axis angle using the isoelectric method? (click on an ECG to view it)


Interpret these challenging cases to the best of your ability. Suggested levels of interpretation:

  1. Icon Transparent Blue.png Describe the axis as normal (positive leads I and II) or abnormal
  2. Icon Transparent Green.png Calculate the axis
  3. Icon Transparent Yellow.png List possible causes (if the axis is abnormal)
  4. Nuvola filesystems services.png Interpret the ECG and case details as a whole to assess the significance of the axis.

Help: For each skill, here is a collection of relevant cases and clinical examples. You can practise these skills and exercises in any order, but the coloured icons (Icon Transparent Blue.pngIcon Transparent Green.pngIcon Transparent Yellow.pngNuvola filesystems services.png) should help you to find examples of a similar difficulty level. Planned future versions of this page should allow you to keep track of which exercises you have completed, for example by exporting the list to Learnist where you can mark each item as 'done'. You can also review the concepts, theory and background knowledge in the 'Review' section above.

Nuvola apps kuser.svg Connect
Active learning exercise:
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Wikiversity is a community devoted to collaborative learning. We build learning resources from the ground up and also link to existing internet resources. By getting involved, you can benefit from powerful educational models including active learning to strengthen your own knowledge, while also helping others around the world to access medical education.

Join in the community:

You can also learn more about the projects that this page is designed to support, including FOAM, Global Open Educational Resources Logo.svg and CC-logo.svg