All About the Coronary Arteries

There are several types of blood vessels in the human body. Most arteries are systemic, meaning they carry oxygenated blood from the heart to the rest of the body. Pulmonary arteries carry blood from the right side of the heart, which is low in oxygen, to the lungs for oxygenation. The left coronary artery feeds blood to the left side of the heart while the right coronary artery transports blood to other blood vessels. Both coronary arteries begin with a width that is roughly equal to that of a drinking straw, around four millimeters. The arteries gradually taper as they descend to other vessels.

The left coronary artery, also known as the left main coronary artery and the left main stem, rises from the aorta above the left side of the aortic valve. It carries blood from the aorta into the left side of the heart. Typically, the left coronary artery is between 10 and 25 millimeters in length and then splits into two other arteries. Occasionally, the coronary artery divides into three, but this is rare. Generally, people use the term "left main artery" to refer to the section of the blood vessel between the aorta and the split. "Left coronary artery" can refer to just this section or the section and all of the subsequent branches.

The right coronary artery originates from the right side of the aorta and is significantly smaller than the left coronary artery. It travels down the right coronary sulcus, which separates the atria of the hearts from the ventricles. Eventually, it branches off into two different arteries. Though rare, it is possible for the right coronary artery to have a different course, including originating from the left side of the aorta. The right coronary artery supplies blood to the ventricles, other arteries, and the nodes. These nodes are responsible for controlling heart rhythm.

There exists a third artery that many physicians consider a coronary artery. This third artery, the conus artery, isn’t present in every person. In addition, it is often small enough that it doesn’t present on scans. The conus artery can provide additional blood flow to the heart when a branching artery from the left coronary artery is unable to do so. The right coronary artery originates from the conus artery.

Both coronary arteries feed into several different branching arteries. The left coronary artery feeds into the left anterior descending artery and the circumflex artery. The left anterior descending artery sends blood to the front portion of the left area of the heart. The circumflex artery circles around the heart and supplies blood to the outer area and rear. The right coronary artery provides blood for the acute marginal artery and the right posterior descending artery. Along with the left anterior descending artery, the right coronary artery delivers blood to the middle of the heart.

Occasionally, physicians may refer to one artery as being dominant over the other artery. Doctors determine this by discovering which artery is supplying the posterior descending artery. If the right coronary artery is supplying the blood, the circulation of blood is right-dominant. If the left coronary artery is supplying it, the circulation is left-dominant. It is also possible for both arteries to supply the blood, making the circulation co-dominant. Most people are right-dominant at 70%, while only 20% of people are co-dominant. This makes left-dominant the rarest at 10% of individuals.

A network of tiny blood vessels is normally not open or active. This network, collateral circulation, opens when the coronary arteries narrow and limit blood flow to the heart, allowing blood to flow along a separate path, avoiding the narrow coronary arteries. This protects the heart tissue from injury while ensuring that it is receiving an adequate amount of blood. Collateral circulation usually becomes active following a heart attack or due to coronary artery disease.

The heart can constrict the coronary arteries depending on how much oxygen it needs. This is vasodilation or vasoconstriction. If the heart demands more oxygen, the arteries widen to allow for more blood flow. If the body cannot provide enough oxygen to meet the demands of the heart, tissue ischemia can develop. This can lead to tissue damage and dysfunction and may cause chest pain or be asymptomatic. Ischemic heart disease is one of the most common causes of death in the majority of Western countries.

Both coronary arteries are incredibly important for medical procedures to protect the heart. Angioplasties use special tubing to insert a balloon up to the coronary arteries. By inflating the balloon, physicians can widen blocked areas to improve blood flow to the heart. In some cases, surgeons will use coronary artery bypass surgery to improve blood flow. For this procedure, they take healthy sections of vein from legs or artery from the wrists and place them above and below the blockage. This allows blood to flow through the new paths instead.

A popular alternative name for the anterior interventricular branch of the left coronary artery is the widowmaker. The term sometimes refers to the entirety of the left coronary artery or any number of blockages of the artery. Because the left coronary artery is responsible for supplying large amounts of blood to the heart, any blockage can lead to sudden death. Survival times for a widowmaker heart attack range from a few minutes to several hours.