Pacemaker Health Dictionary

A cardiac or arti?cial pacemaker is a device that helps a faulty HEART to maintain normal rhythm. It consists of a battery that stimulates the heart by an electric current passed through an insulated wire which is attached either to the surface of the ventricle (epicardial pacemaker) or to the heart lining (endocardial pacemaker). In a normal heart, the regular electrical impulses are initiated by a special area of tissue (sinoatrial node). A cardiac pacemaker is used when a person’s sinoatrial node is malfunctioning or when there is interference with the passage of normal impulses. Some devices send out signals at a ?xed rate; others monitor the rate and, when it falters in any way, stimulate regular contractions. Implantation is carried out under a local anaesthetic, and the lithium batteries can last for several years. People with pacemakers should avoid any source of powerful electromagnetic radiation – radio or radar transmitters or airport security screens. (See also CARDIAC PACEMAKER.)

n. 1. a device used to produce and maintain a normal heart rate in patients who have *bradycardia. The unit consists of a battery that stimulates the heart through one or more insulated electrode wires (*leads) attached to the surface of the ventricle (epicardial pacemaker) or lying in contact with the lining of the heart (endocardial pacemaker). The pacemaker senses when the natural heart rate falls below a predetermined value and then stimulates the heart (demand pacemaker). A pacemaker may be used as a temporary measure with an external battery or it may be permanent, when the whole apparatus is surgically implanted under the skin. In most cases the right atrium and right ventricle are paced (dual-chamber pacing), but in a proportion of patients only right ventricular (single-chamber) pacing is required. 2. the part of the heart that regulates the rate at which it beats: the *sinoatrial node.