The Facts

• In a healthy heart, heartbeat is controlled by a group of cells in the top of the heart called the sinoatrial (SA) node, according to the National Heart, Lung and Blood Institute. This node sends out an electrical signal that coordinates heart contraction and the pumping of blood.
  
  

Purpose

• Pacemakers achieve their effects by overriding or correcting faulty electrical signals inside the heart, notes the NHLBI.
  
  

Generating Power

• The main body of an artificial pacemaker--called a pulse generator--gains its power from an onboard battery, which in turn supplies associated electrical circuitry, according to the Mayo Clinic.
  
  

Electrical Pulses

• In response to unwanted changes in heart rhythm, compensatory pulses from the pacemaker's electrical circuitry travel from the main unit to the heart through attached insulated wires called leads, reports the Mayo Clinic.
  
  

Biventricular Pacemakers

• Individuals with heart failure (inadequate pumping of blood) may receive a biventricular pacemaker, notes the Mayo Clinic. This type of pacemaker sends simultaneous electrical signals to both of the heart's main pumping chambers (ventricles) to help reset their pumping rhythm.