A PVC that originates from the base of the heart and activates toward the apex will show what deflection in the inferior leads?

• A. Positive in inferior leads
• B. Negative in inferior leads
• C. No deflection in inferior leads
• D. Biphasic in inferior leads

Answer: (A)

The key idea is that the QRS deflection in a lead reflects the direction of the depolarization wavefront. Inferior leads (the ones placed on the bottom) are oriented to detect activity toward the feet. If a PVC originates in the base of the heart and the activation propagates toward the apex, the depolarization vector points downward toward the inferior region. That downward direction makes the QRS complexes in the inferior leads upright (positive). If the wavefront were moving away from the inferior leads, you’d see negative deflections; if it were perpendicular, you might get a small or biphasic deflection.