Automatic Implantable Cardiac Defibrillators.

Since its first human application in 1980, the automatic implantable cardioverter defibrillator (ICD) has undergone remarkable advances leading to expanded acceptance. Originally indicated only for patients who had survived two cardiac arrests, the devices have recently been shown to improve survival in all patients with prior myocardial infarction and an ejection fraction of 30% or less. The devices have been miniaturized and are now implanted transvenously, often with hospital discharge within 24 hours of surgery. The ICD is now considered standard therapy for the prevention of life-threatening arrhythmias. Current versions not only treat ventricular arrhythmias with pacing and shock therapy, but some versions also have the capability to treat and suppress atrial arrhythmias, resynchronize the ventricles to manage heart failure symptoms, or pace the heart with all the features of a dual chamber pacemaker. Technologic advances have dramatically expanded the indications for ICD implantation.