These are pacemakers and defibrillators that are placed using a special “third” lead place behind the major pumping chamber (left ventricle) of the heart. This technology has been shown to improve the function of this chamber in the majority of patients in whom they are implanted.

The procedure involves implanting a half-dollar sized pacemaker usually just below the collarbone. Three wires (leads) connected to the device monitor the heart rate to detect heart rate irregularities and emit tiny pulses of electricity to correct them. In effect, it is "resynchronizing" the heart.