The sinoatrial nodal artery, sinoatrial nodal artery or sinoatrial artery is an

artery An artery () is a blood vessel in humans and most other animals that takes oxygenated blood away from the heart in the systemic circulation to one or more parts of the body. Exceptions that carry deoxygenated blood are the pulmonary arteries in ...

of the

heart The heart is a muscular Organ (biology), organ found in humans and other animals. This organ pumps blood through the blood vessels. The heart and blood vessels together make the circulatory system. The pumped blood carries oxygen and nutrie ...

which supplies the

sinoatrial node The sinoatrial node (also known as the sinuatrial node, SA node, sinus node or Keith–Flack node) is an ellipse, oval shaped region of special cardiac muscle in the upper back wall of the right atrium made up of Cell (biology), cells known as pa ...

, the natural pacemaker center of the heart. It is usually a branch of the

right coronary artery In the coronary circulation, blood supply of the heart, the right coronary artery (RCA) is an artery originating above the right cusp of the aortic valve, at the Aortic sinus, right aortic sinus in the heart. It travels down the right coronary su ...

. It passes between the right atrium, and the opening of the

superior vena cava The superior vena cava (SVC) is the superior of the two venae cavae, the great venous trunks that return deoxygenated blood from the systemic circulation to the right atrium of the heart. It is a large-diameter (24 mm) short length vei ...

Anatomy

Origin

It arises from the

in around 60% of individuals, from the left circumflex coronary artery in about 40% of individuals, and in less than 1% of humans, the artery has an anomalous origin directly from the

coronary sinus The coronary sinus () is the largest vein of the heart. It drains over half of the deoxygenated blood from the heart muscle into the right atrium. It begins on the backside of the heart, in between the left atrium, and left ventricle; it begi ...

descending aorta In human anatomy, the descending aorta is part of the aorta, the largest artery in the body. The descending aorta begins at the aortic arch and runs down through the chest and abdomen. The descending aorta anatomically consists of two portions o ...

, or distal

. The origin of the sinoatrial node artery is not related to coronary artery dominance, which means the side (right or left) that provides the circulation to the back of the heart. In contrast, the

atrioventricular nodal branch The atrioventricular nodal branch is a coronary artery that supplies arterial blood to the atrioventricular node, which is responsible for initiating muscular contraction of the ventricles. The AV nodal branch is most often a branch of the right ...

, that is the artery that brings blood to the

atrioventricular node The atrioventricular node (AV node, or Aschoff-Tawara node) electrically connects the heart's atria and ventricles to coordinate beating in the top of the heart; it is part of the electrical conduction system of the heart. The AV node lies at the ...

, depends on coronary artery dominance.

Course

In more than 50% of human hearts, the artery actually courses close to the superior posterior aspect of the

interatrial septum The interatrial septum is the wall of tissue that separates the right and left atria of the heart. Structure The interatrial septum is a that lies between the left atrium and right atrium of the human heart. The interatrial septum lies at ang ...

. The sinoatrial node surrounds the sinoatrial artery, which can run centrally (in 70% of individuals) or off-center within the node.

Variation

A left S-shaped sinoatrial artery, originating from the proximal left circumflex or LCx artery, has been described as a common variant in approximately 10% of human hearts. This artery is larger than normal and supplies a good part of the

left atrium The atrium (; : atria) is one of the two upper chambers in the heart that receives blood from the circulatory system. The blood in the atria is pumped into the heart ventricles through the atrioventricular mitral and tricuspid heart valves. ...

, but also right-sided structures like part of the

and the atrioventricular nodal areas. In this variant, the artery courses in the sulcus between the left superior pulmonary vein and the

left atrial appendage The atrium (; : atria) is one of the two upper chambers in the heart that receives blood from the circulatory system. The blood in the atria is pumped into the heart ventricles through the atrioventricular mitral and tricuspid heart valves. T ...

where it could be susceptible to injury during catheter or surgical ablation procedures on the left atrium, especially for atrial fibrillation ablation or open-heart cardiac surgery.

Additional images

File:Gray492.png , Sternocostal surface of heart (

visible at left)

References

{{Authority control Arteries of the thorax