Axis Deviation
Learn about the appearance of left and right axis deviation
The normal cardiac axis runs from the SAN to in between 30 degrees above lead I and the line of aVF (hence the readings from aVR should be negative). If it's outwith this then this is called axis deviation.
In order to check the axis we look at lead 1 and aVf.
- Both positive (normal axis)
- Lead 1 positive but aVf negative (left axis deviation)
- Lead 1 negative but aVf positive (right axis deviation)
- Both negative (extreme axis deviation - check leads on correct sides or if patient has dextrocardia)
Normal Axis:
Right Axis Deviation:
This is where the axis runs between +90 and +180 degrees
QRS is positive in III and aVF and negative in I and aVL
This is normally caused b right ventricular hypertrophy but can also be caused by a left posterior hemiblock ( a block in the left posterior bundle of the left bundle branch).
Left Axis Deviation:
The axis runs between -30 and -90 degrees
QRS is positive in leads I and aVL and negative in II and aVF
