Lead I = left (0 degrees)
Lead aVF = floor (90 degrees)
Lead I +ve and Lead aVF +ve = Between 0-90 degrees (Normal axis)
Lead I -ve and Lead aVF +ve = Between 90-180 degrees (Right axis deviation)
Lead I +ve and Lead aVF -ve = Between 0 to -90 degrees (possible Left axis deviation)
Lead I -ve and Lead aVF -ve = Between -90 to 180 degrees (Extreme axis)
However, normal axis is -30 to 90 degrees. So, when Lead I is +ve and Lead aVF is -ve, the axis is between 0 to -90 degrees. By lookin at lead II, we can find possible left axis deviation.
In such cases:
- If lead II +ve = 0 to -30 degrees (Normal axis)
- If lead II -ve = -30 to -90 degrees (Left axis deviation)