i have a question: If you're completely dependant on a pacemaker, how does it know you're doing strenuous activity? Does it sense that your ventricles need to pump harder somehow?
In my case, only the ventricles are 100% dependent on the pacemaker. So the pacemaker "listens" to my atria and responds accordingly to speed up the ventricles. HOWEVER, there is also a "feature" (one I happen to hate) that has a motion sensor of sorts, for those who need it for the atria as well. If it feels your body "bouncing" it assumes you're walking or exerting yourself in some way and increases your heart rate. The docs swear by it, but the two times I've had it turned on I've HATED it. The first time I had to ride a bus to downtown for jury duty and the bumpiness of the bus had my HR at 120 the whole way! They claim it shouldn't do that if it's set right, but since my HR increases on its own with exercise, I prefer to let it handle that side of things!