The normal QRS axis typically lies in which quadrant and range?

The normal QRS axis typically lies in which quadrant and range?

• A. Lower right quadrant, 0 to 90 degrees
• B. Upper left quadrant, -180 to -90 degrees
• C. Lower left quadrant, -90 to 0 degrees
• D. Upper right quadrant, 90 to 180 degrees

Answer: (A)

The direction of the QRS axis is the average orientation of ventricular depolarization, expressed as an angle on the hexaxial reference system. In this system, 0 degrees points to the right, and +90 degrees points downward. So 0 to +90 degrees sits in the lower-right quadrant. In healthy individuals, the mean QRS axis commonly falls in this region, making it the typical normal range. That’s why this option is the best choice: it specifies the normal quadrant and the commonly cited range for axis within the normal spectrum. If the axis shifted into the lower left (negative angles) or the upper regions (positive near 180 degrees or more), that would indicate left- or right-axis deviations, respectively, which are not considered normal.