Heart blockage is a problem that occurs when there is an abnormal heart rhythm. In this condition, the heart beats way too slow as compared to a normal beating rhythm, the heartbeat is driven with an electrical signal that comes from the sinoatrial node, located at the top of the right atrium. The signal travels through the atria and reaches the atrioventricular node, which tells the heart to contract and pump blood. Heart block occurs when this electrical signal is delayed or interrupted. It is also known as the atrioventricular block (AV block).