There are many causes of abnormal heart rhythms (arrhythmias). Some arrhythmias are harmless and do not need treatment. Sometimes arrhythmias stop on their own or with changes in lifestyle, such as avoiding alcohol, caffeine (in beverages and foods), and smoking. Other arrhythmias are dangerous or bothersome enough to need treatment. Artificial pacemakers are one type of treatment. Other treatments for arrhythmias include insertion of an implantable cardioverter-defibrillator (ICD), cardioversion-defibrillation, use of antiarrhythmic medications, or destruction of a small area of heart tissue that is responsible for the arrhythmia (ablation).
Artificial pacemakers are electronic devices that act in place of the heart’s own pacemaker, the sinoatrial node. These devices are implanted surgically under the skin, usually below the left or right collarbone. They are connected to the heart by wires (leads) running inside a vein. The tips of the wires are implanted in the wall of a heart chamber. The pacemaker sends an electrical signal that makes the heart muscle contract. Sometimes only one wire is placed, typically in the right ventricle. Other pacemakers use 2 or more wires so that different chambers can be paced. Pacemakers typically can sense the person's heart rate and rhythm and send a pacing signal only when it is needed. Most pacemakers are programmable from outside the body so that doctors can change how they respond.
The low-energy circuitry and battery designs allow pacemaker units to function for about 10 to 15 years.
Some people may be candidates for leadless pacemakers. With this type of pacemaker, no wires are needed to connect the pacemaker to the heart. Doctors make a small incision in the groin and use a catheter to insert the pacemaker directly into the bottom right heart chamber (the right ventricle).
There is almost no risk of interference with pacemakers from cell phones, automobile ignition systems, radar, microwaves, and airport security detectors. However, some equipment may interfere with pacemakers. Examples are electrocautery devices used to stop bleeding during surgery, diathermy (physical therapy treatments that use radiowaves to apply heat to muscles), and sometimes magnetic resonance imaging (MRI). MRI may be safe with certain types of pacemaker, depending on how they are constructed.
Keeping the Beat: Artificial Pacemakers
Artificial pacemakers are electronic devices that act in place of the heart’s natural pacemaker (the sinus or sinoatrial node). They generate electrical impulses that initiate each heartbeat. Pacemakers consist of a battery, an impulse generator, and wires that connect the pacemaker to the heart. An artificial pacemaker is implanted surgically. After a local anesthetic is used to numb the insertion site, the wires that connect the pacemaker are usually inserted into a vein near the collarbone and threaded toward the heart. Through a small incision, the impulse generator, which is about the size of a silver dollar (about 1.5 inches or 4 centimeters in diameter), is inserted just under the skin near the collarbone and connected to the wires. The incision is stitched closed. Usually, the procedure takes about 30 to 60 minutes. The person may be able to go home shortly afterward or may briefly stay in the hospital. The battery for a pacemaker usually lasts 10 to 15 years. Nevertheless, the battery should be checked regularly. Battery replacement is a quick procedure. There are different types of pacemakers. Some take over the control of the heart rate, overriding the electrical impulses generated by the heart. Others, called demand pacemakers, allow the heart to beat naturally unless it skips a beat or begins to beat at an abnormal rate. Still others, called programmable pacemakers, can do either. Some pacemakers can adjust their rate depending on the wearer’s activity, increasing the heart rate during exercise and decreasing it during rest. |
The most common use of pacemakers is to treat slow arrhythmias. When the heart slows below a set threshold, the artificial pacemaker begins to produce electrical impulses. Less commonly, pacemakers are used to treat fast arrhythmias by delivering a series of impulses to decrease the heart rate by converting the fast arrhythmia back to normal.
Cardiac resynchronization therapy (CRT) is another use for pacemakers. In some people with heart disorders, the 4 heart chambers do not follow their normal, orderly sequence of contractions. Special pacemakers with 3 leads, one each to pace the right atrium, the right ventricle, and the left ventricle, can restore the normal sequence of contractions and improve outcome in some people with heart failure.
