This document provides instructions on how to determine the electrical axis of the heart from an electrocardiogram (ECG). It explains that the electrical axis shows the general direction of electricity in the heart from right to left. It describes the orientation of the limb and augmented leads around the heart and how their deflections relate to the electrical axis, with Lead I typically positive and AVR typically negative in a normal axis. Deviations of the axis to the left or right can be identified by comparing the deflections of Leads I and AVF.

1. ECG BASICS 1
HOWTO DETERMINETHE AXIS

2. WHY?
• WHY SHOULD I DETERMINETHE AXIS AS MY
FIRST STEP IN INTERPRETATION?
• BECAUSE IT STARTSTO GETYOUTHINKING
ABOUT WHATTHE PROBLEM MAY BE

3. HOW DO I DO IT?
• FIRST WE NEEDTO KNOWTHE BASIC LIMB LEADS
• NAMELY :- LEADS I , II , III,AVL,AVR & AVF
• CANYOU REMEMBERTHEIR ORIENTATION
AROUNDTHE HEART?
• AREYOU SCRATCHINGYOUR HEAD RIGHT
NOW?

4. LETS LOOK AT
THE HEART
THIS ISTHE HEART INTHE
SAGITTAL PLANE

5. THE NORMAL ELECTRICAL
AXIS
• THIS ISTHE GENERAL
NORMAL DIRECTION OF
ELECTRICITY INTHE
HEART
• ITS FROM RIGHTTO LEFT

6. NOW WE HAVETO IMAGINE
WE ARETHE ELECTRODES
• EACH ELECTRODE
LOOKS ATTHE HEART
FROM A PARTICULAR
DIRECTION
AVR
AVF
AVL

7. SO FOR AVR
• AVR ALWAYS SEES A NET
MOVEMENT OF
ELECTRICITY AWAY
FROM ITSELF
AVR

8. SO?
SO ITS DEFLECTION IS
ALWAYS NEGATIVE

9. SO FOR AVL AND AVF
• THEYTENDTO SEE A
MORE POSITIVE
DEFLECTION
AVF
AVL

10. SO?
SOTHEIR DEFLECTIONS
ARE MAINLY POSITIVE OR
BIPHASIC

11. LETS NOT FORGETTHE
OTHER 3
• USINGTHE SAME
PRINCIPAL WE CAN
NOW PLACETHE
AUGMENTED LEADS
AROUNDTHE HEART
III II
I

12. AND USING WHAT WE
LEARNT BEFORE
• LEAD 1 SHOULD SEE A POSITIVE
DEFLECTION
• LEAD II SHOULD SEE A POSITIVE
DEFLECTION
• LEAD III SHOULD SEE A BIPHASICTO
NEGATIVE DEFLECTION

13. NOW WE GET A BIT MORE
TECHNICAL

14. IF WE PLOT
THESE ONTO
A BODY
THESE ARETHE ANGLES
THAT EACH OFTHE LEADS
SIT AT
WITHTHETHICKER LINE
BEINGTHE NORMAL AXIS
1
AVL
IIAVF
III
AVR

15. LETS SIMPLIFY

16. IF WE
CONSIDER
ONLYTHESE 2
LEADS
IN A NORMAL AXISTHEY
SHOULD ONLY SEE
POSITIVETO MAINLY
POSITIVE DEFLECTIONS
1
AVF

17. BOTH UP
NORMAL AXIS
I AVF

18. IFTHE AXIS
SHIFTSTOTHE
LEFT
AVF NOW SEESTHE
ELECTRICITY MOVING
AWAY
AND I SEES IT STILL AS
POSITIVE
1
AVF

19. I UP AVF DOWN
LEFT AXIS DEVIATION
I AVF

20. IFTHE AXIS
SHIFTSTOTHE
RIGHT
AVF NOW SEESTHE
ELECTRICITY MOVING
TOWARDS IT
AND I SEES IT AS MOVING
AWAY
1
AVF

21. I DOWN AVF UP
RIGHT AXIS DEVIATION
I AVF

22. AND IFTHERES
EXTREME
RIGHT AXIS
DEVIATION
BOTH NOW SEETHE
CURRENT MOVING AWAY
1
AVF

23. I DOWN AVF DOWN
EXTREME RIGHT AXIS DEVIATION
I AVF

24. GOT IT
LETSTRY A FEW

25. THE AXIS IS?
WHICH WAY ARE 1 AND AVF POINTING?

26. THATS RIGHT,A NORMAL
AXIS

27. TRYTHIS ONE
REMEMBER ONLY CONSIDER 1 AND AVF

28. THATS RIGHT,A RIGHT AXIS
DEVIATION

29. TRYTHIS ONE
REMEMBER ONLY CONSIDER 1 AND AVF

30. THATS RIGHT,A LEFT AXIS
DEVIATION

31. TRYTHIS ONE
REMEMBER ONLY CONSIDER 1 AND AVF

32. THATS RIGHT,AN EXTREME
RIGHT AXIS DEVIATION