Pacemakers are electronic devices that may stimulate either the upper chambers of the heart (atria), lower chambers (ventricles) or both. In addition, some pacemakers are built with an internal device that can shock the heart back into a regular rhythm in the event a dangerous arrhythmia (implantable cardioverter defibrillator).
Pacemakers are most commonly used to correct an abnormally slow heartbeat by sending electrical impulses to one or more chambers of the heart.
