Basic guide: What is a pacemaker?

A pacemaker is a small device that’s placed in the chest or abdomen to help control abnormal heart rhythms. The device uses electrical pulses to prompt the heart to beat at a normal rate.

Your heart has its own internal electrical system that controls the rate and rhythm of your heartbeat. With each heartbeat, an electrical signal spreads from the top of your heart to the bottom, and as the signal travels, it causes the heart to contract and pump blood.

Pacemakers are used to treat arrhythmias — problems with the rate or rhythm of the heartbeat. During an arrhythmia, the heart can beat too fast, too slow, or with an irregular rhythm, and pacemakers use low-energy electrical pulses to overcome this faulty electrical signaling.

A heartbeat that’s too fast is called tachycardia, while a heartbeat that’s too slow is called bradycardia.

During an arrhythmia, the heart may not be able to pump enough blood to the body. This can cause symptoms such as fatigue (tiredness), shortness of breath, or fainting. Severe arrhythmias can damage the body’s vital organs and may even cause loss of consciousness or death.

What is a pacemaker
The image shows a cross-section of a chest with a pacemaker. Figure A shows the location and general size of a double-lead, or dual-chamber, pacemaker in the upper chest. The wires with electrodes are inserted into the heart’s right atrium and ventricle through a vein in the upper chest. Figure B shows an electrode electrically stimulating the heart muscle. Figure C shows the location and general size of a single-lead, or single-chamber, pacemaker in the upper chest.

A pacemaker can relieve some arrhythmia symptoms, such as fatigue and fainting, and a pacemaker also can help a person who has abnormal heart rhythms resume a more active lifestyle.

What pacemakers can do
  • Speed up a slow heart rhythm.
  • Help control an abnormal or fast heart rhythm.
  • Make sure the ventricles contract normally if the atria are quivering instead of beating with a normal rhythm (a condition called atrial fibrillation).
  • Coordinate electrical signaling between the upper and lower chambers of the heart.
  • Coordinate electrical signaling between the ventricles. Pacemakers that do this are called cardiac resynchronization therapy (CRT) devices. CRT devices are used to treat heart failure.
  • Prevent dangerous arrhythmias caused by a disorder called long QT syndrome.

Pacemakers can be temporary or permanent. Temporary pacemakers are used to treat short-term heart problems, such as a slow heartbeat that’s caused by a heart attack, heart surgery, or an overdose of medicine. Permanent pacemakers are used to control long-term heart rhythm problems.

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How does a pacemaker work?

A pacemaker consists of a battery, a computerized generator, and wires with sensors (electrodes) at their tips. The battery powers the generator, and both are surrounded by a thin metal box. The wires connect the generator to the heart.

A pacemaker helps monitor and control the heartbeat. The electrodes detect the heart’s electrical activity and send data through the wires to the computer in the generator. If the heart rhythm is abnormal, the computer will direct the generator to send electrical pulses through the wires to reach the heart.

Newer pacemakers can also monitor blood temperature, breathing, and other factors, and can even adjust the heart rate to changes in activity. The pacemaker’s computer also records the heart’s electrical activity and heart rhythm. A doctor will use these recordings to adjust the pacemaker so it works better for the patient.



A doctor can program the pacemaker’s computer with an external device — and, fortunately, he or she doesn’t have to use needles or have direct contact with the pacemaker.

Pacemakers have one to three wires that are each placed in different chambers of the heart.

  • The wires in a single-chamber pacemaker usually carry pulses from the generator to the right ventricle (the lower right chamber of the heart).
  • The wires in a dual-chamber pacemaker carry pulses from the generator to the right atrium (the upper right chamber of the heart) and the right ventricle. The pulses help coordinate the timing of these two chambers’ contractions.
  • The wires in a biventricular pacemaker carry pulses from the generator to an atrium and both ventricles. The pulses help coordinate electrical signaling between the two ventricles. This type of pacemaker also is called a cardiac resynchronization therapy (CRT) device.
Types of pacemaker programming
Pediatric X-ray depicting the endocardial pacemaker inserted through the right subclavian vein.
Pediatric X-ray depicting the endocardial pacemaker inserted through the right subclavian vein.

The two main types of programming for pacemakers are demand pacing and rate-responsive pacing.

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A demand pacemaker monitors the heart rhythm. It only sends electrical pulses to the heart if it is beating too slow or if it misses a beat.

A rate-responsive pacemaker will speed up or slow down the heart rate depending on activity levels. To do this, the device monitors the sinus node rate, breathing, blood temperature, and other factors to determine activity level.

How will a pacemaker affect the patient’s lifestyle?

Once someone have a pacemaker, he or she will have to avoid close or prolonged contact with electrical devices or devices that have strong magnetic fields. Devices that can interfere with a pacemaker include:

  • Cell phones and MP3 players (for example, iPods)
  • Household appliances, such as microwave ovens
  • High-tension wires
  • Metal detectors
  • Industrial welders
  • Electrical generators

These devices can disrupt the electrical signaling of a pacemaker and stop it from working properly — and the patient may not be able to tell whether the pacemaker has been affected.

How likely a device is to disrupt a pacemaker depends on how long the person exposed to it and how close it is to the pacemaker. To be safe, some experts recommend not putting a cell phone or MP3 player in a shirt pocket over the pacemaker (if the devices are turned on). The patient may also want to hold a cell phone up to the ear that’s opposite the site where the pacemaker is implanted. If someone straps a MP3 player to his or her arm while listening to it, put it on the arm that’s farther from the pacemaker.

Patients can still use household appliances, but avoid close and prolonged exposure, as it may interfere with the pacemaker.

Someone with a pacemaker can walk through security system metal detectors at a normal pace. Security staff can check with a metal detector wand as long as it isn’t held for too long over the pacemaker site. Anyone with a pacemaker should avoid sitting or standing close to a security system metal detector. (Notify security staff if you have a pacemaker.)

Also, people with pacemakers should stay at least two feet away from industrial welders and electrical generators.

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Some medical procedures can disrupt a pacemaker, including:

  • Magnetic resonance imaging, or MRI
  • Shock-wave lithotripsy to get rid of kidney stones
  • Electrocauterization to stop bleeding during surgery

Let all of the doctors, dentists, and medical technicians know that you have a pacemaker. The doctor can give you a card that states what kind of pacemaker you or the patient has. Anyone with a pacemaker should always carry that card in a wallet, and may want to wear a medical ID bracelet or necklace that states that he or she has a pacemaker.

In most cases, having a pacemaker won’t limit people from doing sports and exercise, including strenuous activities. He or she ma, however, need to avoid full-contact sports, such as football — such contact could damage the pacemaker or shake loose the wires. Talk to the doctor how much and what kinds of physical activity are safe.

Ongoing pacemaker care

A doctor will want to check a pacemaker regularly (about every three months). Over time, a pacemaker can stop working properly because:

  • Its wires get dislodged or broken
  • Its battery gets weak or fails
  • Heart disease progresses
  • Other devices have disrupted its electrical signaling

To check a pacemaker, the doctor may ask the patient to come in for an office visit several times a year, although some pacemaker functions can be checked remotely using a phone or the Internet. The doctor also may want to get to have an EKG (electrocardiogram) to check for changes in the heart’s electrical activity.

Pacemaker batteries last between 5 and 15 years (an average of 6 to 7 years), depending on how active the pacemaker is. A doctor will replace the generator along with the battery before the battery starts to run down. Replacing the generator and battery is less-involved surgery than the original surgery to implant the pacemaker, though the pacemaker wires also may need to be replaced eventually.





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