ECG: Causes of Axis Deviations

The normal axis is generally between -30 and +90 degrees.Right axis deviation is defined as axis located between 90 degrees and 180 degrees. Left axis deviation defined as the axis located between -30 degrees and -90 degrees.
The left table summaries the easy way to determine the cardiac axis (http://sitemaker.umich.edu/ecgtutorial/axis)

Left axis deviation
Left bundle branch block
Atrial spetal primum defect
Wolf-parkinsons white disease Type A
Inferior MI
Left anterior hemiblock
(N.B: LVH itself does not cause Left axis deviation)

Right axis deviation
Maybe normal variant in young adults
Right bundle branch block
Acute right heart strain - e.g. PE
Left posterior hemiblock
Right ventricular hypertrophy - e.g. Chronic lung disease +/- pulmonary hypertension
Dextrocardia
Anterolateral Myocardial Infarction
Wolff-Parkinson Wright Syndrome Type B
Atrial septal defect secundum
Severe pulmonary stenosis
Fallot's tretralogy / VSD

Tutorial link: https://courses.stu.qmul.ac.uk/smd/kb/resources/ECG_workshop/session2.htm