The High Tech Heart: What to Expect from a Pacemaker
The heart has a "natural pacemaker" the sinoatrial (SA) or sinus node that produces bioelectrical impulses that cause the heart to beat regularly. If there is a problem with the SA node, the heartbeat can become too slow (bradycardia), too fast (tachycardia) or irregular (arrhythmia). When this occurs an artificial pacemaker may be considered to correct the problem.
An artificial pacemaker replaces the natural pacemaker or overcomes a blockage of the heart's electrical pathways. Some artificial pacemakers are permanent, installed under the skin during surgery, and some are temporary, applied externally. The implantation procedure requires only a local anesthetic, and takes about an hour.
A pacemaker consists of a battery-powered generator and the wires that connect it to the heart. The generator, which is about the size of a silver dollar and has an effective life of seven to 12 years, is implanted just beneath the skin below the collarbone. The wires are then threaded into position through veins leading back to the heart. Most pacemakers have a device that senses when the heartbeat reaches a certain level; they then turns themselves off until the heartbeat slows again, usually to 60 beats per minute, and then resume working. These are called "demand" pacemakers.
A more sophisticated type of pacemaker actually monitors a number of physical changes in the body that signal an increase or decrease in activity. If the heart's own pacing system fails to respond properly, these pacemakers slowly raise or lower the heartbeat to the appropriate level, usually from 60 to 100 beats per minute.
We may still see warnings posted in public places when there is a microwave oven nearby, such as convenience stores. Today, however, pacemakers are shielded from these electromagnetic forces and have a backup mechanism if a very strong electromagnetic field does manage to disrupt the programming.
Most people report little or no trouble with the procedure. Soreness or scarring is usually minimal.
American Heart Association, National Heart, Lung, and Blood Institute.