I have a friend who has a pacemaker/defibrillator has had for a number of years and in the last few weeks is getting plus rates of 36 and 38 we think this is abnormal because when the Dr. put it in he explained to us it was supposed to keep it around 60 bpm
He/She should contact the pacemaker clinic they attend. Whenever I have had a problem or a question they have had me in quickly. If they have had it for a number of years the battery may be running down though at the previous check they should have said how much life is left in the battery.
Of course electrical interference can also cause problems like having your phone in shirt or jacket breast pocket.
pace maker has some problem
maybe battery
it shold be fixed