A pacemaker is a small device implanted in the chest and connected to the heart through specialized wires. It is used to generate an artificial heart rhythm. I often have to place a pacemaker if there is a dangerously slow or unreliable heart rhythm, or if a slow rhythm is a barrier to using more effective medications. Modern pacemakers are quite sophisticated and will not interfere with your microwave oven. Their batteries can last a decade or more.