implantable cardioverter-defibrillator (ICD), a surgically implanted electric device that automatically terminates lethal ventricular arrhythmias by delivering low-energy shocks to the heart, restoring proper rhythm when the heart begins beating rapidly or erratically. About the size of an audiotape cassette, the device can be implanted without thoracotomy in many cases. It is attached to the abdomen or chest wall with a wire link to the heart.
