Automatic Implantable Cardioverter Defibrillator (AICD/ICD): ICD’s have been very useful in preventing sudden death in patients with known, sustained ventricular tachycardia or fibrillation. Studies have shown that they may have a role in preventing cardiac arrest in high risk patients who have not had, but are at risk for, life-threatening ventricular arrhythmias. A battery-powered pulse generator is implanted in a pouch under the skin of the chest or abdomen, often just below the collarbone. Wires or leads run from the pulse generator to positions on the surface of or inside the heart. When the ICD detects ventricular tachycardia or fibrillation, it shocks the heart to restore the normal rhythm.