Atrioventricular node

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Overview
The atrioventricular node (abbreviated AV node) is an area of specialized tissue between the atria and the ventricles of the heart, which conducts the normal electrical impulse from the atria to the ventricles.

The AV node is also known as the Aschoff-Tawara node.

Function
The AV node receives two inputs from the atria: posteriorly via the crista terminalis, and anteriorly via the interatrial septum.

An important property that is unique to the AV node is decremental conduction, in which the more frequently the node is stimulated, the slower it conducts. This is the property of the AV node that prevents rapid conduction to the ventricle in cases of rapid atrial rhythms, such as atrial fibrillation or atrial flutter.

The atrioventricular node delays impulses for ~0.1 second before allowing impulses through to the His-Purkinje conduction system, which spreads impulses to the ventricular walls. The reason it is important to delay the cardiac impulse is to ensure that the atria have ejected their blood into the ventricles before the ventricles contract.

Blood supply
The blood supply of the AV node is from a branch of the right coronary artery in 85% to 90% of individuals, and from a branch of the left circumflex artery in 10% to 15% of individuals. When the RCA supplies the AV node, the coronary system is said to be "right dominant," and when the AV node is supplied by the LCX, the system is "left dominant."