A pacemaker is a device that helps regulate the heartbeat. The device, smaller than a matchbox, is placed under the skin near the collarbone. A wire extends from the pacemaker to the heart.
If a pacemaker detects an abnormally slow heart rate (bradycardia) or no heartbeat, it emits electrical impulses that stimulate the heart to speed up or resume beating.
A pacemaker is often implanted if medications to prevent arrhythmia or control the heart rate result in an excessively slow rate, and following AV node ablation.