Normal QRS axis?

Normal QRS axis ?
a) +30 to 110°
b) -30 to +110°
c) +110° to +150°
d) -110° to -150°
Correct Answer - B
Ans. is ‘b’ i.e., -30 to +110°
In a normal heart, the average direction of the vector during spread
of the depolarization wave through the ventricles, called the mean
QRS vector, is about +59 degrees.
This means that during most of the depolarization wave, the apex of
the heart remains positive with respect to the base of the heart.
The normal electrical axis of the heart (mean electrical axis or mean
QRS vector) lies between -30° and + 100°.
If the axis is more negative than -30° it is called left axis deviation,
whereas if the axis is more positive than + 100°, it is called right axis