What is the function of an implantable cardioverter-defibrillator?

Shock the heart: The device has the abiltiy to sense when your heart is beating in an abnormal and dangerous way which could lead to you passing out or having your heart stop. It then delivers an electric shock to the heart to convert the abnormal rhythm back to normal. The device also can function as a pacemaker if your heart beat becomes too slow.

Terminate arrhythmia: These are devices which may detect and automatically treat malignant (life-threatening) arrhythmias. Those include ventricular tachycardia and ventricular fibrillation. They use either bursts of rapid pacing or one or more high energy shocks. Patients receive these either after an arrhythmic event or prophylactically because they are at risk for these arrhythmias.