ECG: how to determine left and right axis deviation?

First lets revise the basics of ECG related to axis deviation :

• Normal if QRS complexes positive deflection in lead I or II
• Lead I is 0 degree and lead II is +60 degree
• Normal cardiac axis lies between -30 deg to 90 deg
• Deflection moves towards the positive direction.
• In a normal ECG with no axis deviation in both lead I and II QRS complexes have positive deflection that is to upward direction.


To determine axis deviation remember that you need primarily information of lead I and lead II only, and forget the rest.

Now if QRS complex in lead I and II are negative and positive respectively what will be the axis deviation – right or left?

Answer: as we said do determine axis deviation we need to move towards positive direction, here we will move from lead I to lead II i.e. from 0 degree to +60 degree. Since this is a clockwise movement towards the right side this is a right axis deviation (RAD).


If QRS complex in lead II and I are negative and positive respectively what will be the axis deviation – right or left?

Answer: as we said do determine axis deviation we need to move towards positive direction, here we will move from lead II to lead I i.e. from +60 degree to 0 degree. Since this is an anti-clockwise movement towards the left side this is a left axis deviation (LAD).

This was a simplification effort of the topic made by the author. Hope you find it useful. Crosscheck the issue from standard textbooks.

 

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