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Dr. Mete ALPASLAN
Abnormalities of Electrical Axis
Determination of electrical axis is especially useful for the diagnosis of the following:
 
Left anterior fascicular block
(left anterior hemiblock).
 
Left posterior fascicular block
(left posterior hemiblock).
 
Ventricular tachycardia (VT)
(the deviation of electrical axis by at least 40 degrees to left or to right during wide QRS tachycardia supports the diagnosis of
VT
).
 
Right ventricular hypertrophy
.
Left axis deviation is observed in
  normal variants.
 
left ventricular hypertrophy
 
left anterior fascicular block
 
left bundle branch block
  some types of
ventricular tachycardias
  some congenital heart diseases (
tricuspid atresia
, endocardial cushion defect).
Right axis deviation is observed in
  normal variants (may be normal in infants)
 
right ventricular hypertrophy
 
left posterior fascicular block
 
lateral myocardial infarction
 
emphysema
(the heart assumes a more vertical position when anteroposterior chest diameter increases)
  asthenia
 
acute pulmonary embolism
 
dextrocardia
Extreme right axis deviation (indeterminate axis, northwest region, no man's land)
  is between
-90
and
180
degrees.
 
QRS
complexes are
negative
in leads
I
and
aVF
.
  Infants with
Ostium Primum type atrial septal defect (ASD)
or
Atrioventricular (AV) canal defect
may show extreme right axis deviation.