Left axis deviation (LAD) occurs when additional electrical forces move to the left or when the time required for the electrical activity to move over the ventricle is prolonged.
LAD is the most common ECG abnormality occurring in almost 10% of the adult population. LAD is considered normal in pregnant women and those with emphysema. A tall, thin person will have a fairly vertical heart showing a right axis shift. A short, broad person will have a fairly horizontal heart showing a left axis shift.
Other causes of LAD include:
Left anterior hemiblock
Inferior myocardial infarction (inferior wall heart attack)
Hyperkalaemia (high potassium)
Wolff Parkinson White syndrome
Ostium primum atrial septal defect
Left bundle branch block
Left ventricular conduction defects
Left atrial hypertrophy
Right ventricular ectopic rhythms
Chronic Obstructive Pulmonary Disease (COPD)
Ascites (fluid in the abdominal cavity)
Hypertension (high blood pressure)
Aortic stenosis or regurgitation
Left ventricular hypertrophy (some sources claim that LVH does not cause LAD)
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