Carolyn Murphy, age 13, of Whittier, N.C., for her question:
WHAT IS A PACEMAKER?
If doctors discover a disturbance in the heart's rhythm, which is called arrhythmia, chemicals are usually the first choice in attempting to correct the disturbance. Sometimes the rate is too slow or too fast. Certain types of drugs are available that can help to speed up a rate that is too slow, or slow down one that is too fast.
In most cases, the human heart has its own system for regulating the heartbeat. Occasionally a condition known as a heart block develops when this system is disturbed and the normal impulse from the atrium to the ventricle is interrupted. If the problem is more than a temporary one, with drugs not being able to correct the trouble, then often an electronic device called a pacemaker is used to correct the heart block.
A pacemaker is an electronic device which artificially stimulates heart action in order to regulate the heart rate. The unit was first introduced in 1956 by Dr. Paul toll of Beth Israel Hospital in Boston, Massachusetts.
A pacemaker consists of a small device which is implanted in the body. The device transmits an electric impulse to the heart, stimulating it to beat in a regular manner. Many pacemakers are powered by batteries that must be replaced about every two years.
A pacemaker unit is wired most often to the inner surface of the heart, but sometimes to the outer surface instead. For connection to the inner surface, the wire is threaded down through the jugular vein into the interior of the right ventricle. For connection to the otuer surface, the chest is penetrated surgically.
Implantation of a pacemaker is easy for most patients.
The equipment is used in patients ranging from tiny tots to elderly people.
In the 1970s, surgeons began implanting nuclear powered and rechargeable battery powered pacemakers. The nuclear models are expected to last 10 years or even longer before needing replacement. The rechargeable models are expected to last for the patient's entire lifetime. In some models, batteries will have to be replaced surgically after they have worked in a patient's body for five years or longer.
The simplest type of pacemaker is used for some patients whose heart rate is constantly slow. This type operates at a fixed rate of beat, set before installation. Patients who must have variable heart rates use a ''demand'' pacemaker. This type fires only when the heartbeat is slower than a predetermined critical rate.