Heart Pacemaker A heart pacemaker is used primarily to correct some types of bradycardia, or slow heart rhythms. The pacemaker is implanted in the body, usually below the collarbone, where it monitors the heart rhythm and supplies electrical triggers to the heart if it is beating too slowly. The pacemaker is composed of a small metallic pulse generator that contains a battery and electrical circuitry and one or two leads (wires) that carry the electrical signals to the heart and allow the pacemaker to trigger heartbeats. Pacemakers must be replaced every five to 10 years, which is about how long the batteries last, and must be checked a couple of times a year. What to Expect Pacemaker implantation takes about two to three hours in the EP lab. A two-inch incision is made beneath the collarbone and a small "pocket" is created for the pulse generator. Then the leads are inserted into the heart through a large vein that runs under the collarbone. Once the leads are positioned in the heart, the leads are attached to the pulse generator. During the procedure, the nurse will give you pain medication and a sedative to be certain you are comfortable. Following the procedure, your arm will be in a sling overnight. You will receive detailed follow-up instructions before you leave the hospital. It is important that you follow these instructions and call your doctor or nurse with any questions. You also will need to carry a pacemaker ID card with you, which will alert medical personnel in the event of an emergency.