Bradycardia is a condition of the heart, where the heart is beating in a (sometimes irregular) rhythm that is too slow to maintain sufficient supply of oxygenated blood throughout the body. Such conditions may be caused by dysfunctions of the sino-atrial (SA) node, the atrio-ventricular (AV) node, or other parts of the heart's conduction system. In these cases bradycardia therapy aims at restoring a regular sinus rhythm and sufficient heart rate through battery-powered devices (referred to as pacemakers or implantable pulse generators [IPG]) using small electrical impulses delivered through leads directly to the heart in an effort to stimulate heart muscle cells externally, when intrinsic stimulation fails or is unreliable.