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Cardiac Pacemaker

  • An implantable device that delivers an electrical pulse to the heart to regulate a slow heart rate
  • Used to treat conditions that cause the heart to beat too slowly
  • May be implanted permanently or temporarily
  • Involves electrophysiology & cardiac arrhythmia medicine, cardiovascular medicine
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Cardiac Pacemaker


A cardiac pacemaker is a small device implanted in a person’s chest that provides an electrical pulse to the heart, as needed, to regulate a slow heart rate.

As people age, some may experience a slower-than-normal heart rate caused by electrical problems or blockages within the heart. When the heart rate slows considerably, it can cause worrisome symptoms, such as dizziness and shortness of breath. A pacemaker can help to restore a person’s slow heart rate to a normal one, reducing or eliminating these symptoms.

Up to 3 million Americans live with pacemakers, and most are older adults—more than 70% of people who get pacemakers are at least 65 years old.

What is a cardiac pacemaker?

A pacemaker is a small, battery-powered device used to correct a slower-than-normal heart rate (a condition known as bradycardia). It is surgically implanted in a person’s chest or abdomen, where it can send electrical impulses to the heart to help it beat at a steady, healthy rate.

The heart runs on electrical activity. In a healthy person, the part of the heart that naturally maintains rhythm is called either the sinus node or sinoatrial node. This “natural pacemaker” sends electrical signals through the heart that make its upper chambers contract, pushing blood through to its lower chambers and keeping the heart beating at a normal rhythm.

Sometimes, however, the sinus node stops working efficiently. It may lose momentum, which slows down a person’s heart rate, or a blockage may develop in the heart, which slows down or disrupts the electrical pulses traveling through the heart. In both instances, a pacemaker may be needed to help a person’s slow heart rate resume to a normal, steady speed. Once implanted, the device may last up to 15 years before it needs to be replaced.

Although pacemakers may sometimes be used as a temporary measure, such as during a medical emergency, they typically remain permanently in place.

Some pacemakers, called biventricular pacemakers, can treat heart failure. They may also operate as implantable cardioverter defibrillators, designed to shock the heart and return it to a normal rhythm when it beats too quickly or abnormally.

How does a cardiac pacemaker work?

The pacemaker battery powers the electrical impulses sent to the heart to help speed up a slow heart rate. A pacemaker contains sensors that track its rhythm, using this data to determine when and how often to send electrical pulses, based on your circumstances, including your activity level, at any given moment.

A pacemaker consists of two parts:

  • Pulse generator: This is the larger portion of the device that contains the battery
  • Leads: These are wires that connect the pulse generator to the heart. A pacemaker may have one to three leads, depending on its model and function.

Most pacemakers are implanted in the left side of a person’s chest. Doctors make an incision in the chest, where they insert the pulse generator. Then, the leads are inserted through a blood vessel in the chest, thigh, or neck and threaded through blood vessels until they reach the heart.

Each lead is attached to the heart in the upper or lower chambers at one end and to the pulse generator at the other end. When the pacemaker sensor recognizes a too-slow heart rhythm, it sends an electrical pulse from the pulse generator through the lead to the heart, prodding it to beat at a normal rate.

A new type of pacemaker, called a leadless pacemaker, is smaller than a typical pacemaker and doesn’t have any leads or wires. It is placed directly in the heart’s right ventricle (one of the heart’s lower chambers), where it is fastened in place with screws or tines.

Doctors regularly monitor patients with pacemakers to ensure that the device continues to function optimally.

What conditions is a cardiac pacemaker used to treat?

A pacemaker is used to treat the following heart conditions that cause the heart to beat too slowly:

A pacemaker will not be recommended when a slower-than-normal heart rate is temporary or can be corrected with medication or lifestyle changes. However, when other treatments aren’t effective, a pacemaker can improve a person’s heart rhythm and quality of life.

What are the risks associated with a cardiac pacemaker?

As with any surgical procedure—although uncommon—it’s possible to have complications during or after the procedure to implant a pacemaker. Arrhythmia, bleeding, or an infection at the site of the incision are examples of rare complications.

Occasionally, a pacemaker may stop working properly due to damage or a battery problem. If you notice symptoms such as dizziness or shortness of breath after you have had a pacemaker implanted, call your doctor.

Is there anything patients should avoid if they have a pacemaker?

If possible, people with a pacemaker should avoid the following:

  • High-voltage power lines
  • Radio transmitters
  • Metal detectors
  • Handheld security wands in the airport; carry an ID card indicating that you have a pacemaker
  • Magnetic resonance imaging (MRI) machines
  • Magnetic therapy massagers, pillows, or other devices
  • Gas-powered appliances
  • Leaning over a running car engine if the hood is open

Some medical tests and therapies can be harmful to pacemakers. If you have a pacemaker, ask your doctor if the following are appropriate for you:

  • MRI studies
  • Radiation therapy for cancer treatment
  • Shock wave lithotripsy, a treatment for kidney stones
  • Short-wave or microwave diathermy, which may treat pain or muscle spasms

In a medical emergency, health care providers need to know that you have a pacemaker. Consider wearing a medical ID bracelet or carrying a card in your wallet with details about your pacemaker. You should also let your doctor and pharmacist know you have a pacemaker.

This article was medically reviewed by Mark Schoenfeld, MD.