What does demand mode pacing do?

• A. Fires continuously at a set rate
• B. Fires only when the heart rate drops below a preset rate
• C. Is used only in emergencies
• D. Disables other pacing modes

Answer: (B)

Demand mode pacing is designed to monitor the heart's intrinsic activity and provide electrical stimulation only when the heart rate falls below a predetermined threshold. This ensures that the pacemaker or pacing device supports the heart's natural rhythm rather than overriding it. In situations where the heart rate is inadequate or drops below the set rate, the demand mode will trigger pacing to maintain an appropriate heart rate.

This mode is particularly useful because it helps to maximize the efficiency of the heart's own pacemaker while providing assistance only when necessary. It strikes a balance between allowing normal heart function and ensuring that the patient does not experience significant bradycardia (slow heart rate).

Other options describe pacing functions that do not align with the nature of demand mode pacing. Continuous pacing at a set rate or using pacing only in emergencies does not reflect the demand-based nature of this mode, which operates on the principle of responding specifically to the heart's needs. Additionally, demand mode does not disable other pacing modes but rather provides a selective response based on the heart's activity.