These high-tech small devices are used for many purposes ranging from preventing heart rate slowing to treating heart failure, to heart pumping to preventing sudden deaths.There are basically three types of pacemakers: single-cable and 2-wire batteries that prevent heart rate deceleration, 3-wire batteries used for heart failure therapy, and defibrillators that save lives by delivering an electroshock if the heart can not function as a high-tied heart pump.The pacemaker is applied to people with heart rhythm disorders who can not sustain their lives normally.