Pacemakers: Generating regular heartbeats

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Pacemakers: Generating regular heartbeats

Pacemakers correct slow, irregular or weak heart beats.

Your doctor has recommended that you get a pacemaker. You're not alone. Pacemakers are common, with more than 3 million of these small devices in use worldwide and about 600,000 implanted each year.

People need pacemakers for a variety of reasons — mostly due to one of a group of conditions called arrhythmias, in which the heart's rhythm is abnormal. One of the most common problems requiring a pacemaker is a heart rate that's too slow, which is known as bradycardia. Almost any heart condition can lead to bradycardia by disrupting the heart's natural electrical system, which controls your heartbeat.

Normal aging of the heart may disrupt your heart rate, making it beat too slow or irregularly. Heart muscle damage resulting from a heart attack is another common cause of abnormalities of the heart rate or rhythm. Some medications can affect the heart rate as well. For some, genetic conditions cause an abnormal heart rate.

Regardless of the underlying cause of a slow heart rate, a pacemaker — a small, battery-powered device implanted in your chest — may correct it, offering substantial relief.

Your natural pacemaker

To appreciate how a pacemaker works, it helps to understand your heart and the electrical system that makes it beat.

The heart is a muscular, fist-sized pump with four chambers, two on the left side and two on the right. The upper chambers are the right and left atria. The lower chambers are the right and left ventricles.

For your heart to function properly, the heart's chambers must operate in a coordinated fashion. In addition, your heart must beat at an appropriate rate — normally from 50 to 100 beats a minute in adults. If your heart beats too slowly or rapidly, not enough blood is pumped to your internal organs, leading to fatigue, fainting, shortness of breath, confusion and other symptoms.

Your heart's electrical system controls the chambers' pumping action. A normal heartbeat begins in your right atrium, in the sinus node. This cluster of cells — your natural pacemaker — acts like a spark plug, generating regular electrical impulses that travel through specialized muscle fibers.

When an electrical impulse reaches the right and left atria, they contract and squeeze blood into the ventricles. After a split-second delay to allow the ventricles to fill, the impulse reaches the ventricles, making them contract and pump blood to the rest of your body.

Chambers of the heart

Illustration of chambers of the heart

Working as a precisely coordinated team, the four chambers of your heart — two ventricles and two atria — keep blood flowing properly through your heart and body.

The conduction system

Illustration of the conduction system

Your heart's natural pacemaker — the sinus node — produces electrical impulses that prompt your heart to beat.

Special precautions

Because modern pacemakers are more sophisticated than their predecessors, pacemaker malfunction due to interference from electronics and security systems is rare. Still, a few precautions are in order:

  • Cellular phones. It's safe to talk on a cell phone, but avoid placing your cell phone directly over your pacemaker implantation site when the phone is turned on. Although unlikely, your pacemaker could misinterpret the cell phone signal as a heartbeat and withhold pacing, producing symptoms such as sudden fatigue.
  • Security systems. Passing through an airport metal detector won't interfere with your pacemaker, although the metal in it may sound the alarm. But avoid lingering near or leaning against a metal-detection system. If security personnel insist on using a hand-held metal detector, ask them not to hold the device near your pacemaker any longer than necessary or ask for an alternative form of personal search. To avoid potential problems, carry an ID card stating that you have a pacemaker.
  • Medical equipment. If a doctor is considering any medical procedure that involves intensive exposure to electromagnetic energy, tell him or her that you have a pacemaker. Such procedures include magnetic resonance imaging, therapeutic radiation for cancer treatment, and shock wave lithotripsy, which uses shock waves to break up large kidney stones or gallstones. If you're having surgery, the electrocautery procedure that controls bleeding also can interfere with pacemaker function.
  • Power-generating equipment. Stand at least two feet from welding equipment, high-voltage transformers or motor-generator systems. If you work around such equipment, your doctor can arrange a test in your workplace to determine whether it affects your pacemaker.

Devices that present little or no risk to pacemaker function include microwave ovens, televisions and remote controls, radios, toasters, electric blankets, electric shavers and electric drills.

Once considered a novelty, pacemakers are now a standard treatment for many conditions affecting your heart's electrical system. By restoring your heart's normal rhythm, pacemakers can alleviate symptoms such as fatigue, lightheadedness and fainting. Because most of today's pacemakers automatically adjust your heart rate to match your level of physical activity, they can allow you to resume a more active lifestyle.

Last Updated: 10/13/2006
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