My dads defib/pace maker combination unit gives him about 780volts, but I must add it has saved his life a few times. No magnetic fields are allowed around it, with one exception.
FYI as an EMT in the ER we use a magnet (these are NOT carried in an ambulance, only the heart Doc's apply them NOT us) to disable the unit. As the on/off switch is activated that way so they don't have to cut them open to stop it from misfiring during a test, or replacement.
So those warnings are not only to prevent an accidental shock, they could mess up the unit as well. It would be a real shame to have it stop working, and not know until you found out the hard way
sign me, the Man with too many side jobs