Implantable Cardiac Defibrillators are similar to pacemakers and the surgery required to place them is much the same. These are used for treatment of episodes of rapid heartbeat and/or fibrillation; especially of the lower chambers of the heart. They prevent episodes of sudden cardiac death because of arrhythmia. They do this by either pacing or shocking the heart internally.
Bi-Ventricular Pacing is used either in combination with pacing or implantable cardiac defibrillator therapy. This involves placing a third wire on the left side of the heart at the time of pacemaker or defibrillator implantation. This is added if a significant degree of congestive heart failure and low left ventricular function is present.