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Pacemakers

What is a pacemaker?

An artificial pacemaker is a small device that helps your heart beat in a regular pattern at a normal rate, if it doesn't do so naturally. A battery in the pacemaker sends pulses of electricity through wires to your heart to stimulate a consistent heartbeat. Pacemakers can be temporary or permanent, depending on your individual condition. A doctor must implant a permanent pacemaker directly into the chest, but a temporary device is worn externally.

Why would I need a pacemaker?

Heartbeats are too important to leave to chance. Instead of contracting at random, the cells in your heart wait for a special electrical signal. A section of the upper right chamber of your heart, called the sinus node, fires waves of electricity that tell the heart when to beat. Ideally, these electric jolts are regular, dependable, and perfectly spaced to keep you active and healthy.

Unfortunately, the signals aren't always reliable, and if your natural pacemaker system breaks down, you may need an artificial one to take over the job. Artificial pacemakers are often prescribed to patients with sick sinus syndrome, a condition that makes the heart beat too slowly and, occasionally, too quickly. You may also need a pacemaker if something is blocking the flow of electricity across your heart, a condition called heart block. These conditions can occur after a heart attack, or may be a consequence of the aging process. Without treatment, heart block can cause a slow, uncoordinated heartbeat. A pacemaker can also help correct a wide variety of other abnormal heart rhythms (arrhythmias). More than 500,000 Americans are living with artificial pacemakers, and the number is steadily rising.

What is the difference between the two types of pacemakers?

If you have a temporary problem with heart rhythm (a common condition for patients recovering from a heart attack), you may need just a temporary pacemaker. Your doctor can attach a small device to your skin that sends an electronic signal to your heart.

Most pacemakers, however, are implanted in the body. Each implantable pacemaker has two main parts, a "pulse generator" that emits the electrical signal and one or two "leads," or wires that carry the electricity to the heart. The pulse generator, about the size of three stacked poker chips, usually sits below the collarbone. The leads are threaded through large veins until they reach the heart.

Early pacemakers produced the same unwavering rhythm at all times, but thanks to computer technology, today's pacemakers are much more flexible and adaptable. For instance, some devices turn on only when your heart rate drops below a certain level. These are called demand pacemakers. Other devices, known as rate-adaptive pacemakers, automatically increase your heart rate when you exercise and slow down when you rest -- just like a healthy heart does.

A study by researchers from Johns Hopkins University suggests that the newer pacemakers can make a real difference for heart failure patients. In a review of studies involving over 1,600 patients who used the latest model pacemakers, the researchers found that the patients' risk of death from heart failure decreased by 51 percent, while hospitalizations decreased by 29 percent.

How are pacemakers implanted?

It's a simple procedure -- nothing even close to the trauma of open-heart surgery. Your doctor will probably give you a local anesthetic, which means you'll be awake for the whole procedure. She'll first make a small cut underneath your collarbone. Then, with the help of an x-ray machine, your doctor will guide the lead or leads through your veins to the appropriate place on your heart. She will then slip the generator (fully programmed for your needs) into the slot below your collarbone. The incision will be sewn up, and you will probably be able to go home the next day.

After your pacemaker is implanted, you'll need to have it checked and adjusted periodically. This is easy and painless. In fact, a technician may even be able to monitor your pacemaker over the telephone. For this, you simply wear a transmitter connected to a pair of wristbands. Then you hold the phone over your transmitter, and place a special magnet over your pacemaker. The technician can then check your heart rate, the general functioning of the pacemaker, and the life of the device's battery. The batteries in most pacemakers usually run out after about six years. When this happens, the whole device has to be replaced.

What precautions do I have to take with my pacemaker?

Once your pacemaker is in place, your heart should beat just like a normal, healthy heart. For this reason, most people with pacemakers can exercise just as hard and as often as anyone else does. Of course, some people with pacemakers have other heart problems that may make exercise risky. Your doctor will tell you how much exercise is safe for you.

Despite what you may have heard, household devices such as microwave ovens, electric blankets, electric shavers, and remote controls won't interfere with your pacemaker. You can safely use a cell phone, but you shouldn't hold it over your chest or carry it over your chest while it's activated. Likewise, you can safely walk past surveillance devices at the doors of department stores or libraries, but you probably shouldn't linger.

Some medical devices and treatments really can harm your pacemaker. Your doctor may need to take extra precautions before performing any magnetic resonance imaging (MRI), extracorporeal shock-wave lithotripsy (a procedure to remove kidney stones), radiofrequency ablation (used to control arrhythmias), transcutaneous electrical nerve stimulation (TENS, a treatment for chronic pain), or radiotherapy for cancer. To protect yourself, make sure every doctor who treats you knows about your pacemaker. You should also carry a card in your wallet to alert medical personnel that you're wearing one.

References

Pacemakers: Timing is everything. Mayo Clinic Health Letter. Dec. 1999. 17(12): 1-3.

Pacemakers. American Heart Association. http://www.americanheart.org/Heart_and_Stroke_A_Z_Guide/pacem.html Guidelines for implantation of cardiac pacemakers and antiarrythmia devices. American Heart Association. 1998. http://www.americanheart.org/Scientific/statements/1998/049804-I.html

Bradley DJ, et al. Cardiac resynchronization and death from progressive heart failure: a meta-analysis of randomized controlled trials. JAMA 2003 Feb 12;289(6):730-40.

National Heart, Lung, and Blood Institute. What Is a Pacemaker? May 2008. http://www.nhlbi.nih.gov/health/dci/Diseases/pace/pace_whatis.html

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