The Micra Transcatheter Pacing System is the world’s smallest pacemaker, minimizing the overall size into a device the size of a vitamin pill. As with traditional pacemakers, Micra treats a slow heart rate by delivering electrical signals to stimulate cardiac muscle and restore its rhythm. Unlike most pacemakers that are placed in a patient's chest with electrical leads running to the heart, this device is a leadless pacemaker because it's implanted directly into the heart. This allows Micra to eliminate the major sources of complications with traditional pacemakers, that being the electrical lead and implantable pulse generator. Since this device is completely self-contained within the heart, there is no bump under the skin and no chest scar. [from Medtronic]