The heart is a muscular pump located in the thoracic (chest) cavity. It is constantly working to circulate blood throughout the body. During times of physical exertion or emotional stress, the activity of the heart increases. Due to its constant action, the heart needs a good supply of oxygen and nutrient rich blood to sustain the muscle tissue. This is supplied to the heart via the coronary arteries.
The coronary arteries branch off from the major artery of the heart – the aorta. There are two main coronary arteries, namely the right and left coronary artery. It arises from the aortic sinuses above the aortic valve just as the ascending aorta leaves the heart. Each coronary artery gives off a number of branches that supply the entire heart. The coronary artery distribution may vary, sometimes slightly or at other times significantly, among people.
Right Coronary Artery
This artery arises from the right aortic sinus and supplies the following parts of the heart :
- Right atrium
- Most of the right ventricle
- Diaphragmatic surface of the left ventricle
- Part of the IV septum
- Sinoatrial and atrioventricular nodes
The right coronary artery is able to supply all these parts of the heart by giving off the following branches :
- Sinoatrial nodal artery
- Right marginal artery
- Atrioventricular nodal artery
- Posterior descending artery (posterior interventricular artery)
Left Coronary Artery
This artery arises from the left aortic sinus and supplies the following parts of the heart :
- Left atrium
- Most of the left ventricle
- Part of the right ventricle
- Most of the IV septum
- Sinoatrial node (if not supplied by the right coronary artery)
The left coronary artery is able to supply all these parts of the heart by giving off the following branches :
- Circumflex artery
- Sinoatrial nodal artery
- Left marginal artery
- Left anterior descending artery (anterior interventricular artery)
Picture from Wikimedia Commons
Coronary Artery Dominance
Depending on where the posterior descending artery originates, the heart’s blood supply may be right-dominant, left-dominant or co-dominant.
Most people (approximately 70%) are right dominant meaning that the posterior descending artery arises form the right coronary artery. About 15% of people are left dominant meaning that the posterior circumflex artery arises from the circumflex branch of the left coronary artery. In about 20% of people, the area supplied by the posterior descending artery is supplied by branches from both the right coronary artery and the circumflex branch of the left coronary artery. This is known as co-dominance.
Coronary Artery Variations
Apart from the difference with the posterior descending artery that will determine coronary artery dominance, other variations include :
- Sinoatrial node supplied by the right coronary artery or left anterior descending branch of the left coronary artery.
- The circumflex branch arises from the right coronary artery.
- A single coronary artery.
- An accessory coronary artery.