The UCSF-John Muir Health Jean and Ken Hofmann Cancer Center at the Behring Pavilion is now open.  LEARN MORE >

Implantable cardioverter defibrillators (ICDs) are small devices, about the size of a pager, that are placed under the skin just below the collarbone. Small, flexible wires, called leads, monitor the heart's rhythm continuously. If the heart beats too quickly, the lower chambers of the heart (ventricles) will not have enough time to fill with blood. This decreases the ability of the heart to pump blood to the body. Left unchecked, the rapid heartbeat causes death. The ICD device issues a lifesaving jolt of electricity to restore the heart's normal rhythm and prevent sudden cardiac death. This jolt is describes by individuals as a "kick in the chest." ICDs can act as pacemaker when a heart beat that is too slow (bradycardia). If the heart beats to slow the ICD sends tiny electrical impulses to create a more normal heart rate. ICD pacing signals are not felt and cause no discomfort.


ICDs have a tiny computer inside that keeps a record of the heart's activity and remembers when an abnormal heart rhythm occurs. With this information, the electrophysiologist (a doctor who specializes in arrhythmias), can study the heart's activity.

Treatment Options

When is ICD therapy the right choice?

In the simplest terms, anyone who has had or is at a high risk of having dangerous and life-threatening rhythms (ventricular tachycardia, fibrillation or sudden cardiac arrest) is a candidate for an ICD.

A cardiac arrhythmia specialist (electrophysiologist) should evaluate cardiac patients if they have experienced any of the following:

  • A prior cardiac arrest
  • An episode of rapid heartbeat originating from the lower chambers of the heart (ventricular tachycardia)
  • Ventricular fibrillation (VF), which is similar to VT but is characterized by a heartbeat that is too rapid and is irregular or chaotic
  • Low pumping ability of the heart (decreases ejection fraction)
  • Patients at a high risk for sudden cardiac death (SCD) because of an inherited heart abnormality

John Muir Health Capabilities

John Muir Health is very proud of its Cardiac Rhythm Center. John Muir Health has eight leading cardiac rhythm specialists in the Bay Area on staff at John Muir Medical Center-Walnut Creek and John Muir Medical Center-Concord. These rhythm specialists are cardiologists that completed special training in the care of individuals with heart rhythm problems. Special equipment and well trained staff at John Muir Health are available to care for those with the complex and life-threatening problems.