Pacemakers and Defibrillators

Pacemakers and implantable cardioverter defibrillators (ICDs) are pacing and heart rhythm-control devices that treat arrhythmias and other disturbances of the heart's function. They work by sending and receiving electrical signals to and from the heart to regulate the heart rate.

These devices are increasingly common when medications are not sufficient to either prevent the arryhthmia or control a fast heart rate.

What Do Pacemakers and Defibrillators Do?

Depending on your type of arrhythmia, pacemakers (low energy devices) are used to speed up a slow heart rate while implantable cardiac defibrillators (ICDs) control abnormal or fast heart rhythms by "shocking" the heart back into a normal rhythm.

Pacemakers and ICDs help prevent dangerous arrhythmias as well as coordinate electrical signals between the upper and lower chambers of the heart. Devices that coordinate electrical signaling between the ventricles, or lower chambers, are called cardiac resynchronization (CRT) devices, which are pacemakers used to treat heart failure.


The most common use for pacemakers is to treat bradycardia (a too-slow heart rate which can cause loss of consciousness) and heart block, which occurs if an electrical signal is slowed or disrupted as it moves through the heart. This can happen as part of aging, from damage to the heart from a heart attack, or any condition that disrupts the heart's electrical activity.

Permanent pacemakers are placed inside the chest with the patient under local anesthesia. The pacemaker is usually placed in the upper chest under the skin with a wire threaded into the heart through a vein to allow electrical signals to go back and forth between the heart and the pacemaker.

Implantable Cardioverter Defibrillators (ICDs)

Another type of device used to treat arrhythmias is an implantable cardioverter defibrillator (ICD). In addition to using low-energy electrical pulses, ICDs also use high-energy pulses (also called "shocks") to treat life-threatening arrhythmias.

ICDs are used to treat the heart if it stops beating normally and goes into a rapid, abnormal life-threatening heart rhythm. ICDs can also be used in patients with weak heart muscle who are at risk for developing dangerous heart rhythms.

Patient Resources

Pacemakers & Defibrillators Information Guide

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The Arrhythmia Program at the University of Michigan has been a national and international leader in the treatment of arrhythmias for more than 30 years and focuses exclusively on these patients. Working in tandem with our research department, we are on the cutting edge of new procedures and therapies with many of our physicians among those who help set national standards of care for these patients.To schedule an appointment to discuss your heart arrhythmia or other cardiovascular condition, call us at 888-287-1082, email us at, or visit our Make an Appointment page for more information about what to expect when you call us.