Heart block is also called an atrioventricular (a-tre-o-ven-TRIK-u-ler) or AV block. Heart block occurs when there is a delay or interruption in the flow of electrical signals in the heart. The flow of electrical signals controls the way the heart pumps out blood. Normally, the signals come from the atrium (upper chamber of the heart) then pass through to the ventricle (lower chamber of the heart). The electrical signals spread to the ventricles causing the muscles to pump blood.
With heart block, the electrical signals slow down or do not pass through to the ventricle. This may cause the ventricles to pump blood, but at a slower rate. At first you may not know that you have a heart block. Heart block is often a serious condition that needs immediate treatment.