PACEMAKERS AND THE HEART

The permanent pacemaker that is now used in the practice of cardiology is truly a marvel of technology and has contributed in a major way to saving lives and improving the quality of life for millions of people worldwide.

However, pacemakers were invented only about forty years ago, starting out as a huge battery the size of a refrigerator, which a patient had to pull along with him, while an assistant ran ahead to place the plug in the next available electrical outlet, every twenty feet or so. Since then, amazing changes have taken place in these devices, allowing most people with a pacemaker to function normally and to lead productive lives.

While the initial indications for a pacemaker were strictly for someone with recurrent episodes of syncope (sudden loss of consciousness, often resulting in bodily injury), pacemakers are now used for patients with a variety of rhythm and conduction disturbances, which in turn can cause fatigue, weakness, and light-headedness, unless treatment is provided.

The size of pacemakers has progressively decreased, and current models are not much larger in diameter than a silver dollar. One or two leads (wires) are used for the purpose of direct electrical contact with the heart, usually to the right ventricle, and also to the right atrium if two leads are to be used. Two leads are often used, when possible, to maintain the normal synchronized contraction sequence between the atrial chambers and the ventricles, in order to optimize cardiac performance.

As people age, the specialized conduction tissues which travel throughout the heart can deteriorate, much as the cartilage in the knee can wear away. They have a function analogous to wires, and their malfunction can result in sudden stopping of the heart for several seconds, and also can cause a persistent slow heart rate, which does not increase in proportion to the level of a persons activity, as does the normal heart. This in turn can lead to increased fatigue, reduced functional capacity, and even loss of consciousness.

In these situations, the pacemaker can restore the normal rhythm and timing sequence to the heart, with return of normal levels of energy and activity.

Modern pacemakers are unaffected by most environmental conditions. They do not interact with microwave ovens, and are rarely affected by cell phones unless the phone is on and sitting in a pocket very close to the pacemaker. Pacemakers will sense a high electromagnetic field, such as one would encounter near an arc welder, but such situations are not often encountered in daily life.

The battery life of a pacemaker is in the range of about eight years, after which the generator can be changed during a simple outpatient procedure. By programming the pacemaker to optimal settings, the battery life can often be further extended.

At the Sacramento Heart Center, we have a large pacemaker clinic, and patients usually have their pacemaker evaluated at home every three months. Our pacemaker nurse performs a pacemaker analysis over the telephone, with the patient using a simple device at home which sends the electrical signals from the pacemaker over the telephone to our clinic. A more comprehensive evaluation is annually done in the office.

There are many new and exciting directions the technology of cardiac pacemakers is taking. For example, in combination with electrical ablation techniques, some rhythm disturbances can be completely cured. Special pacemakers, known as defibrillators, are capable of shocking the heart in the presence of a life-threatening rhythm disturbance, with a burst of electricity. Vice President Dick Cheney received one of these defibrillators recently.

Cardiac pacing is now being tested extensively for patients with a severe cardiomyopathy, which means a condition of a weakened and poorly functioning heart muscle. Heart function can be significantly improved by simultaneously pacing two separate sites in the ventricular muscle. Sacramento Heart Center is currently involved in an international research study to learn more about the results of this exciting technique.

If you have any questions about pacemakers, or if you think you may be having symptoms which warrant a search to see if pacemaker therapy is necessary, please call the Sacramento Heart Center at 830-2080.

Dr. Daniel D. VanHamersveld, MD, FACC is affiliated with the Sacramento Heart Center. For more information about the Sacramento Heart Center, call (916) 830-2080 and request information be mailed to you. Please address your cardiology-related questions to "Ask the Cardiologist", 500 University Avenue, Sacramento, CA 95825. Selected questions will be answered in future articles.