What are the causes of left axis deviation (LAD) on ECG?
- Left anterior hemiblock
- Inferior myocardial infarction
- RV apical pacing & middle cardiac vein pacing
- WPW / pre-excitation / bypass tract
- Pulmonary Emphysema
- Ventricular ectopic rhythms
- Mechanical shifts: Expiration, high diaphragm from pregnancy, ascites, abdominal tumors, etc.
- Endocardial cushion defects, some other acyanotic and cyanotic congenital lesions
- Normal variation
Note 1: LVH is not a cause. Left axis deviation is associated with LBBB but LBBB is not a cause of LAD.
Note 2: LAD is does not invariably accompany LVH. Significant LAD suggest presence of myocardial disease in the LV apart from pure hypertrophy.
Marriott 8th ed. 1987 p. 50-55