Atrioventricular node (AV node) is an important part of the electrical conduction system of the heart. Normal functioning of the heart needs regular signal generation and transmission. Signal generation is usual the function of the SA node (sinoatrial node), a small structure situated in the upper part of the right upper chamber of the heart (right atrium). SA node is the natural pacemaker of the heart which generates regular electrical signals with a speed depending on the energy needs of the body. It is under the control of the brain through the nervous system.
Location and function of the AV node
AV node is situated in the lower part of the right atrium near the junction of the upper and lower chambers of the heart. Electrical signals reaching the AV node from the SA node are delayed for a short period, usually less than one fifth of a second before they are transmitted to the lower chambers (ventricles). This delay is needed for the contraction and emptying of the upper chambers before the lower chambers start contracting. The upper chambers of the heart receive the blood and pass it on to the lower chambers which pump it to the body. If the natural delay produced by the AV node is not there, contraction of the lower chambers will be earlier, at a time when they have not been fully filled. This will reduced the output of the lower chambers.
Disease of of the AV node
When the AV node is disease, the conduction of signals from the SA node to the lower chambers of the heart becomes defective. If conduction is totally blocked, it is known as complete heart block. The heart rate becomes dangerously slow when there is complete heart block. An artificial pacemaker for the heart is needed when there is complete heart block. When cause of AV nodal disease is temporary as in a heart attack, a temporary artificial pacemaker is used. If the cause of AV nodal disease is permanent, a permanent artificial pacemaker is needed.