Pacemaker battery life can range between five and 15 years, depending on a number of different factors. Generally, the battery is evaluated during a pacemaker check in a doctor's office to get an estimate on how much longer it will function. If it is running low, a replacement will be recommended to ensure that the patient is never without a pacemaker. During replacement, the entire pacemaker unit is replaced, not just the battery, in a procedure similar to that used when the device was originally installed.
One determining factor for the lifespan of pacemaker batteries is the type of device being used. Different manufacturers produce devices with varying ranges of battery life. Modern pacemakers tend to use more energy because the battery does not just deliver shocks to the heart, but also regulates the pacemaker, logs data on heart rhythm, and performs other functions. When a pacemaker is implanted, people will be provided with an estimate on the range of battery life so they have an idea of what to expect from their pacemakers.
Another issue involves how much the device is used. If a patient's pacemaker kicks in only rarely, the batteries may last a very long time. Pacemaker batteries run down fast when the device needs to be activated regularly to keep the heart rhythm going. This is one reason why doctors cannot predict device life at the outset, as every patient's batteries will run down at a slightly different rate.
It is also possible, although rare, for a patient to receive an original implant with defective batteries. Pacemaker batteries are tested before the device is installed, but sometimes testing doesn't reveal an underlying problem and they lose their charge quickly. Likewise, defective equipment can run down the pacemaker batteries rapidly. Extensive testing before surgery is designed to prevent this situation, but it can happen, and it's one reason patients must visit the doctor several times in the weeks immediately after installation to make sure the device is working properly.
When pacemaker batteries run low and need replacing, doctors opt to replace the whole device to provide patients with access to the latest pacemaker model. The leads will also be tested to see if they need to be replaced or if they can be left as they are. Risks of the replacement are similar to those of the original surgery, including infection, bruising at the pacemaker site, and adverse reactions to anesthetics used during the procedure.