Unipolar ECG leads record electrical activity from what?

• A. A SINGLE reference point
• B. Two reference points
• C. Three reference points
• D. Multiple reference points

Answer: (A)

Unipolar ECG leads measure electrical activity at one location and compare it to a single reference point. The reference is typically a virtual point—often Wilson’s central terminal—constructed by combining signals from other electrodes to create a stable single reference. That means each unipolar lead is describing the heart’s activity at its electrode relative to that one reference point. In contrast, bipolar leads use two physical electrodes and record the difference between them, which is why they involve two points rather than a single reference.