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 to control a heart rate that is too slow or too fast.

What Do Pacemakers and Defibrillators Do?

Pacemakers 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 signals 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 a heart rate that is too slow (a condition known as bradycardia) 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 due to heart attack, or any condition that disrupts the heart's electrical activity.

Permanent pacemakers are typically placed in the upper chest under the skin while the patient under local anesthesia. Wires (or leads) connected to the pacemaker are threaded through the veins and implanted into the heart muscle. These wires send tiny electric charges (which cannot be felt) from the pacemaker to the heart as necessary. A pacemaker may have one, two or three leads, depending on the specific heart condition.

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 a weak heart muscle who are at risk for developing dangerous heart rhythms.

The ICD is typically placed under the skin beneath the collarbone or in the abdomen while the patient under local anesthesia. Two thin wires (or leads) connect the device to one or more of the chambers in the heart. When the heart begins to beat irregularly or too fast, the ICD delivers an electric pulse to restore a normal heartbeat.

Make an Appointment

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.