What is the aorta and how does it relate to the heart?
The heart is a fist-sized organ which lies within the chest behind the breastbone (sternum). It is a muscular pump that pushes blood through blood vessels around the body. The heart sits on the diaphragm, the main muscle of breathing, which is found beneath the lungs. The heart is considered to have two sides - the right side and the left side.
The heart has four chambers - an atrium and a ventricle on each side. The two atria are separated by a wall called the atrial septum. The two ventricles are separated by a wall called the ventricular septum. The atria are both supplied by large blood vessels that bring blood to the heart.
Atria have special valves that open into the ventricles. The valve that opens from the right atrium into the right ventricle is called the tricuspid valve. The valve that opens from the left atrium into the left ventricle is called the mitral valve. The ventricles also have valves but in this case they open into blood vessels. The pulmonary valve opens from the right ventricle into the pulmonary artery. The aortic valve opens from the left ventricle into the aorta. The walls of the heart chambers are made mainly of special heart muscle. The different sections of the heart have to squeeze (contract) in the correct order for the heart to pump blood efficiently with each heartbeat.
The heart's main function is to pump blood around the body.
The right side of the heart receives deoxygenated blood (lacking oxygen) from the body. After passing through the right atrium and right ventricle, this blood is pumped through the pulmonary valve and into the pulmonary artery to the lungs. Here blood picks up oxygen and loses another gas called carbon dioxide. Once through the lungs, the blood flows back to the left atrium. It then passes into the left ventricle and gets pumped through the aortic valve into the aorta, the main artery supplying the body. Oxygenated blood is then carried though blood vessels to all the body's tissues. Here oxygen and other nutrients pass into the cells where they are used to perform the body's essential functions.
What happens when there is coarctation of the aorta?
In coarctation of the aorta, there is a narrowing in part of the aorta, usually the upper part of the aorta. This is just after where the arteries that supply blood to the head and arms have branched off. Blood cannot pass as easily through the narrowed part of the aorta. This means that the blood supply to the lower half of the body can be affected (less blood is able to get through). Also, because of the narrowing, the heart works harder to pump and try to squeeze blood through the narrowing. Because the heart is working harder to pump, this can cause blood pressure to rise. Often, someone with coarctation of the aorta will have high blood pressure in their upper body and arms (or one arm) and low blood pressure in their lower body and legs. Also, the muscle walls of the left ventricle can increase in thickness (hypertrophy) because of the extra work that they are having to do.
When a baby is growing inside their mother's womb (uterus), the pulmonary artery and the aorta are joined together by a small blood vessel called the ductus arteriosus. It means that most of the blood leaving the right ventricle bypasses the lungs and passes directly into the aorta. Once the baby is born, the ductus arteriosus closes, usually within the first few weeks of life. If a baby has severe coarctation of the aorta, the only way that blood can pass to the lower half of the body is through the ductus arteriosus. So, when the ductus arteriosus closes in these babies, no blood will get through to the lower half of the body, causing severe symptoms. If nothing is done about this, the baby can die.
Congenital heart disease occurs in about 7 in 1,000 pregnancies and coarctation of the aorta is just one type of congenital heart disease. Around 1 in 2,500 babies have coarctation of the aorta. The condition is twice as common in males as it is in females.
Coarctation of the aorta can occur alone, or it can occur with other congenital heart problems. The other congenital heart problems that coarctation of the aorta most commonly occurs with are either:
- A bicuspid aortic valve (the aortic valve is normally made up of three cusps or flaps, a bicuspid aortic valve only has two cusps); or
- A ventricular septal defect (a condition where there is a hole in the wall - the septum - that separates the two ventricles).
In some babies, coarctation of the aorta can develop as part of a syndrome (a collection of symptoms) that a baby is born with. For example, coarctation of the aorta can be part of Turner syndrome. (This is a genetic condition that only affects girls. It is a chromosome problem. The most characteristic features of the syndrome are being short, having certain physical features, such as a typical facial appearance, and also having ovaries that do not work properly.)
Further reading and references
Balloon angioplasty or stenting for coarctation or recoarctation of aorta; NICE Interventional Procedure Guidance, July 2004
Vijayalakshmi K, Griffiths A, Hasan A, et al; Late hazards after repair of coarctation of the aorta. BMJ. 2008 Apr 5336(7647):772-3.
Ijland MM, Tanke RB; Aortic coarctation. Circulation. 2009 Sep 29120(13):1294-5.
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