I agree with what Ireneo said, and further I don't know what is meant by "rejected the body"... perhaps the doctor said the body rejected the pacemaker. In either case it may have been a simple way of saying the pacemaker could not supported needed heart activity.
my mother passed because the Dr said the pacemaker rejected the body
I don't know how there could be a rejection. It's not "tissue" - human or otherwise. There have been cases of infection from the insertion of the pacemaker. There may even be an occasional rare care of allergic reaction to the metal in the device. Beyond that, I don't know of an auto immune "rejection" of the device.