Never leave the cell phone in a pocket overlying the pacemaker. Patients with pacemakers should avoid powerful electromagnetic fields which may reprogram the pacemaker. The pacemaker generator contains a lithium battery and what is, essentially, a little computer. The generator can communicate with an external device placed on the skin overlying the pacemaker. Through this device, a physician can change the programming of the pacemaker to best suit the individual patient's needs and investigate the status of the pacemaker.
Some pacemakers also report on the performance of the patient's heart.
Pacemakers can also be checked over the telephone. The patient places a device and a magnet over the pacemaker and the pacemaker transmits a signal over phone line that is analyzed in the physicians office. Pacemaker batteries give off warning signals when they are running low on power many months before they actually fail. This can be detected either by a telephone check or by a formal interrogation by the external device mentioned above. Pacemakers are generally checked at least every 3 months to allow plenty of time to change the generator when it is running low on power.