During mapping, what do QS unipolar signals indicate?

During mapping, what do QS unipolar signals indicate?

• A. The wavefront is moving away from the recording electrode.
• B. The wavefront is moving toward the recording electrode.
• C. QS unipolar signals indicate a late activation.
• D. QS unipolar signals indicate a distant region.

Answer: (C)

QS unipolar signals show that the activation wavefront is moving away from the recording electrode, which results in a pure negative deflection with no initial positive deflection. This pattern identifies that the local tissue is activated later in the sequence compared with its surroundings, i.e., late activation. If the wavefront were moving toward the electrode, you would see a positive deflection (an R wave) instead of a QS. QS tells you about timing and direction, not simply about distance from other regions.

QS unipolar signals show that the activation wavefront is moving away from the recording electrode, which results in a pure negative deflection with no initial positive deflection. This pattern identifies that the local tissue is activated later in the sequence compared with its surroundings, i.e., late activation. If the wavefront were moving toward the electrode, you would see a positive deflection (an R wave) instead of a QS. QS tells you about timing and direction, not simply about distance from other regions.