Low battery
You will have your pacemaker or defibrillator battery tested regularly, either in the doctor's office or by telephone. The first test will be one month after the implantation and then every three months. Some manufacturers are able to check the device over the phone, which reduces the need for frequent office visits. As the battery starts to run down, the visits will become more frequent.

Battery replacement
The average life of an ICD is four-six years, depending on the usage. The more times the ICD is needed to pace or shock your heart, the less time it will last. When you have the device replaced with a new generator, the wires that lead from the generator to your heart will be tested. The wires usually last longer than the generator.