The heart is in perpetual motion. In order to maintain this motion, the heart needs its own electrical system which generates its own impulse. This impulse then travels through the heart’s “wires” to the muscles of the lower chambers of the heart (right and left ventricles), telling them to contract and cause a heartbeat. This natural system helps the heart pump in an efficient rhythm. A problem with any part of this system, though – either the heart’s natural “pacemaker” or the wires carrying the impulses – can cause a slow heart rate. An artificial pacemaker may be needed, to reset the heart to the right pace and make sure blood and oxygen are pumped to the brain and other parts of the body.
Information provided by the Heart Rhythm Society website