A pacemaker is a small, battery-powered medical device designed to electrically stimulate the heart muscle in an effort to restore the heart rhythm towards normal.
A pacemaker system consists of two main parts: the pulse generator and pacing leads. The pulse generator houses the battery and electronic circuits (like a small computer). These circuits contain timers that regulate how often the pacemaker must send impulses to stimulate the heart.
The pulse generator is small, measuring approximately 2" x 2" x 1/4" (45mm x 45mm x 6mm) and weighing less than 2 ounces (20-30g).
The pacing leads are flexible, insulated wires that connect to the pulse generator and carry the electronic impulse to the heart. In addition, the leads also carry signals back from the heart to the pulse generator allowing the pulse generator to sense the heart's natural electrical activity.
By sensing the patient's natural rhythm, the pacemaker will only pace the heart when necessary.