Cardiac Conduction System

Your heart pumps blood throughout your body by contracting or squeezing its four chambers in a regular rhythm. Each heartbeat is caused by electrical signals that travel through a specific pathway in your heart. Your heart's electrical signal begins at the sinoatrial node, SA node, in the top right chamber of your heart called the right atrium.

The electrical signal travels through the right and left atria, causing them to contract and help push blood into the lower chambers, your left and right ventricles. The electrical signal slows down at the atrioventricular node, AV node, so that blood from the atria has time to move to the ventricles.

The electrical signal continues down the bundle of His and into the left and right bundle branches located within your ventricles. When the signal reaches your ventricles, it causes your ventricles to contract and pump blood out to the lungs and body. This cycle repeats at a normal rate of 60 to 100 beats per minute, although it can be slower during sleep and faster during exercise.