Implantable Cardioverter Defibrillators (ICDs)
An implantable cardioverter defibrillator (ICD) is a device implanted in the chest to monitor for arrhythmias and, if necessary, to correct episodes of an abnormal heart rhythm.
ICDs are effective over 90 percent of the time in fighting cardiac arrest in those who are at high risk of the deadliest forms of arrhythmias.
About the size of a pager, ICDs are placed below the collarbone to continuously monitor the heart's rhythm through wires or "leads." Sending electrical pulses to the heart when rhythms become dangerously fast, ICDs halt racing beats and prevent sudden cardiac death.
ICDs can also be programmed to function like a pacemaker, another implanted device that corrects an abnormal heart rhythm. However, pacemakers are usually chosen to correct a slow heart rhythm (bradyarrhythmia, an arrhythmia characterized by a heart rate below 60 beats per minute).
ICDs, on the other hand, are generally used to correct a heart rhythm that is too fast (supraventricular tachycardia, a heart rate above 100 beats per minute).
Most ICDs keep track of the heart's activity when an abnormal rhythm occurs. This information can be used by an arrhythmia specialist to study the heart's activity and better diagnose and monitor the underlying conditions causing the patient's arrhythmia.