An Implantable Cardioverter Defibrillator (ICD) is a device that helps control abnormal heart rhythms. The doctor places the Defibrillator just under the skin under the collar bone, and connects the device to the heart with electrical leads. The heart of an adult at rest normally beats 60 to 100 times per minute. If the heart is beating too quickly (tachycardia), the Defibrillator emits quick, low-energy electrical pulses, called cardioversion, to restore a normal heart rate.  If a fatally rapid heartbeat is detected, the Defibrillator emits a powerful electric shock (called defibrillation) to restore a normal heart rate. This device is commonly used for correction of life-threatening ventricular arrhythmias, irregular heartbeats in the lower chambers of the heart that inhibit blood from being pumped properly. Many defibrillators can also now function as pacemakers, emitting low electrical pulses to correct bradycardia, when the heart beats too slowly.