Question: How do pacemakers know when I need a faster heart rate, for example when I am exercising or anxious?
Answer :Pacemakers today are designed to have a function called rate response of pacing. As background, the older varieties of pacemakers were simply designed to recognize when the heart rate got too slow, and when it got too slow, it would turn itself on, start pacing the heart and support the heart at a predetermined rate, usually somewhere in the range of 60 and 70 beats per minute.
What the newer functions do is anticipate a patient's need for an even faster heart rate. So that if one is exercising generally with or without a pacemaker, there is a need for the heart rate to go up to accommodate the heart's output needed by the exercise. In the case of rate response of pacing, the pacemaker is designed to recognize usually movement, sometimes other measures, which anticipate that a higher heart rate will be needed, and then adjust upward the heart rate derived from the pacing, so that the patient who goes into an exercise mode can receive a faster heart rate automatically.