1. Axis Deviation
Chapter 5

2. Limb leads
Frontal plane

3. LIMB LEADS

4. LIMB LEADS

5. Limb leads

6. Definition Left Right Electrical axis...
...the mean direction of the QRS complex
the general direction in the frontal plane towards which the QRS complex is predominately pointed
Left
Right

7. Mean QRS Axis Calculation
The general direction or toward which lead axis the the QRS complex is predominately oriented
Frontal axis
Only involves the 6 limb leads

8. Mean QRS Axis Calculation

9. Mean QRS Axis Calculation
General rule, the mean QRS axis is oriented at right angles (90°) to any lead showing a bi-phasic complex
General rule, the mean QRS axis points midway between any two leads that show tall R waves of equal height

10. Mean QRS Axis Calculation

11. Mean QRS Axis Calculation

12. Mean QRS Axis Calculation

13. Mean QRS Axis Calculation

14. Mean QRS Axis Calculation

15. Normal versus Deviation
Left
3 ?
1 ?
2 ?
Right

16. Axis Deviation
Left
Right

17. Axis deviation ? ?

18. Axis deviation ?

19. Axis deviation ?

20. Causes of Left Axis Deviation
FYI
• left anterior hemiblock
• Q waves of inferior myocardial infarction
• artificial cardiac pacing
• emphysema
• hyperkalaemia
• Wolff-Parkinson-White syndrome - right sided accessory pathway
• tricuspid atresia
• ostium primum ASD
• injection of contrast into left coronary artery
note: left ventricular hypertrophy is not a cause left axis deviation

21. Causes of Right Axis Deviation
FYI
• normal finding in children and tall thin adults
• right ventricular hypertrophy
• chronic lung disease even without pulmonary hypertension
• anterolateral myocardial infarction
• left posterior hemiblock
• pulmonary embolus
• Wolff-Parkinson-White syndrome - left sided accessory pathway
• atrial septal defect
• ventricular septal defect