What is an Implantable Cardioverter Defibrillator ICD?

An ICD (implantable cardioverter defibrillator) is a small device implanted in the chest and delivers a low-energy electrical pulse to the heart to correct dangerous arrhythmias it detects. If it fails to restore a normal heartbeat, the ICD then switches to a high-energy pulse to defibrillate the heart.  An ICD is similar to a  pacemaker, but it’s able to act as both a  pacemaker (low-energy pulses) and a  defibrillator (high-energy pulses), while a  pacemaker can only deliver low-energy pulses.