Coarctation of the aorta
Coarctation of the aorta is a birth defect in which part of the aorta is narrower than usual. If the stricture is severe enough to go undiagnosed, the baby may have serious problems and require surgery or other procedures shortly after birth. For this reason, aortic coarctation is often considered a critical congenital heart disease.
The defect occurs when a baby's aorta does not form properly as the baby grows and develops during pregnancy. Narrowing of the aorta usually occurs in a portion of a blood vessel just after the branching of the arteries supplying blood to the head and arms near the patent ductus arteriosus, although sometimes the narrowing occurs before or after the ductus arteriosus. In some children with coarctation, some of the mucosal tissue of the ductus arteriosus is thought to adhere to the tissue of the aorta. Because the tissue contracts and allows the ductus arteriosus to close normally after birth, this extra tissue can also constrict and narrow the aorta.
Narrowing or coarctation blocks normal blood flow to the body. This can cause backflow of blood into the left ventricle of the heart, forcing the muscles in that ventricle to work harder to push blood away from the heart. Since the narrowing of the aorta is usually located after arteries branch to the upper body, coarctation in this region can lead to normal or high blood pressure and pulsing of blood in the head and arms and low blood pressure and weak pulses in the legs and lower body.
If the condition is very severe, sufficient blood may not reach the lower body. The extra work on the heart can cause the walls of the heart to become thicker in order to pump harder. This leads to weakening of the heart muscle. If the aorta is not enlarged, the heart can become so weak that heart failure can occur. Coarctation of the aorta often occurs with other congenital heart defects.
Causes and risk factors
The causes of heart defects, including coarctation of the aorta, are unknown in most children. Some children develop heart defects due to changes in their genes or chromosomes. Heart defects such as coarctation of the aorta are also thought to be caused by a combination of genes and other risk factors, such as things the mother comes in contact with in the environment, what the mother eats or drinks, or medicines the mother uses.
Diagnosis
Coarctation of the aorta is usually diagnosed after the baby is born. When a defect is diagnosed at an early age, it usually depends on how severe or mild the symptoms are. Newborn screening with pulse oximetry in the first days of life may or may not reveal aortic coarctation.
In children with more serious illness, the first signs usually include:
- pale skin
- irritability
- heavy sweating
- difficulty breathing
Finding a defect is often done during a physical examination. In infants and older adults, the pulse will be noticeably weaker in the legs or groin than in the arms or neck, and a heart murmur—an abnormal breathing sound caused by interrupted blood flow—can be heard through a doctor's stethoscope. Older children and adults with coarctation of the aorta often have high blood pressure in their arms.
Once suspected, an echocardiogram is the most common test used to confirm the diagnosis. An echocardiogram is an ultrasound of the heart that can show problems with the structure of the heart and blood flow through it, as well as how well the heart is working. It will show the location and severity of the coarctation, as well as the presence of other heart defects. Other tests to measure heart function may be used, including chest x-ray, electrocardiogram, MRI, and cardiac catheterization.
Coarctation of the aorta is often considered a critical congenital heart disease because if the narrowing is severe enough and goes undetected, the baby can have serious problems soon after birth. Critical congenital heart disease can also be detected by pulse oximetry screening in newborns. Pulse oximetry is a simple bedside test to measure the amount of oxygen in a baby's blood. Low blood oxygen levels can be a sign of critical congenital heart disease. Newborn screening with pulse oximetry can detect some babies with critical congenital heart defects, such as coarctation of the aorta, before they develop any symptoms.
Treatment
Regardless of the age at which the defect is diagnosed, when symptoms appear, it will be necessary to expand the narrow aorta. This can be done surgically or through a procedure called balloon angioplasty, which is performed during a cardiac catheterization. Balloon angioplasty is a procedure that uses a thin, flexible tube called a catheter that is inserted into a blood vessel and guided into the aorta. When the catheter reaches the narrow area of the aorta, the balloon at the end is inflated to expand the blood vessel. Sometimes a mesh-covered tube (stent) is inserted to keep the vessel open. A stent is more commonly used to initially expand the aorta or to re-expand it if the aorta narrows again after surgery. During surgery to correct coarctation, the narrow part is removed and the aorta is reconstructed or sutured so that blood can flow normally through the aorta.
Even after surgery, children with coarctation of the aorta often have high blood pressure, which is treated with medication. It is important that children and adults with coarctation of the aorta see a cardiologist regularly to monitor their progress and check for other health problems that may develop with age.