A pacemaker is a device the size of a matchbox that is implanted under the skin beneath the collarbone.  It is connected to the heart using wires (leads) threaded through the vein.  Pacemaker implantation takes about 2 hours and is performed under local anesthesia. 

A pacemaker is implanted when the heart is unable to generate electrical impulses--the body's natural battery runs out.

If you have a pacemaker, you will have it checked periodically at the cardiologist's office and over the phone.  A pacemaker's battery usually lasts between five and eight years.