Right axis deviation is most commonly seen with which condition?

• A. RVH
• B. LVH
• C. Left anterior fascicular block
• D. Normal axis

Answer: (A)

Right axis deviation occurs when the overall direction of the heart’s depolarization vector is shifted toward the right in the frontal plane. The most common reason for this rightward shift is increased right ventricular electrical forces, as seen with right ventricular hypertrophy. When the right ventricle enlarges, its activity dominates the QRS vector, pulling the axis toward the right on the ECG.

In contrast, left ventricular hypertrophy strengthens left-sided forces and tends to shift the axis left, while left anterior fascicular block often produces left axis deviation. A normal axis would not show the rightward shift characteristic of right axis deviation.