Heart Rhythm Disorders - University of Minnesota Physicians Heart at Fairview

Implantable Cardioverter Defibrillator (ICD)

An implantable cardioverter defibrillator (ICD) is a small, electronic device that can stop cardiac arrest immediately. Cardiac arrest—when the heart stops pumping blood suddenly—is most frequently caused by an arrhythmia called ventricular fibrillation.

Cardiac arrest is not a heart attack.

Upon detection of the cardiac arrest, the ICD can deliver brief, high-voltage shocks to the heart and terminate what could be a fatal event. The ICD can stop rapid heart racing, called ventricular tachycardia, by delivering bursts of electrical impulses to the heart without shocks. The ICD can also function as a pacemaker.

An ICD cannot prevent a heart attack or increase the strength of the heart muscle, but its pacemaker function may improve the efficiency of the heart’s pumping function by properly timing the contraction sequence of the different heart chambers.

ICDs are implanted for two kinds of patients. If you have survived a cardiac arrest or life-threatening ventricular arrhythmia, an ICD can protect you from dying from a future cardiac arrest. And second, if you are a patient who has not yet had a cardiac arrest but are believed to be at high risk, an ICD would be recommended. This prevention strategy serves patients with poor heart function and some patients with genetic arrhythmia disorders.