Each time the pulses, the heart muscle contracts (pulls inwards) in anticipation of pumping blood around the body. The beat is then sent to a group of cells known as the atrioventricular hub (AV hub). The AV hub relays the hit to the two lower chambers of the heart (the ventricles).
A pacemaker or implantable cardioverter-defibrillator (ICD) is required when something disrupts this procedure and causes an abnormal heartbeat.
















