Coarctation of the aorta is a narrowing of the aorta, the main blood vessel carrying oxygen-rich blood from the left ventricle of the heart to all of the organs of the body.
Coarctation occurs most commonly in a short segment of the aorta just beyond where the arteries to the head and arms take off, as the aorta arches inferiorly toward the abdomen and legs. This portion of the aorta is called the "juxta-ductal" part of the aorta, or the part near where the ductus arteriosus attaches.
The ductus arteriosus is a blood vessel that is normally present in a fetus and has special tissue in its wall that causes it to close in the first hours or days of life. It is thought that coarctation may be caused by the presence of extra ductal tissue extending into the adjacent aorta which results in aortic narrowing as the ductal tissue contracts.
In babies with coarctation, the aortic arch may be small (hypoplastic). Coarctation may also occur along with other cardiac defects, typically involving the left side of the heart. The defects most commonly seen with coarctation are bicuspid aortic valve and ventricular septal defect. Coarctation may also be seen as a part of more complex, single ventricle cardiac defects.
Coarctation of the aorta is common in patients with some chromosomal abnormalities, such as Turner's syndrome.
In the presence of a coarctation, the left ventricle has to work harder, since it must generate a higher pressure than normal to force blood through the narrow segment of the aorta to the lower part of the body. If the narrowing is severe, the ventricle may not be strong enough to perform this extra work resulting in congestive heart failure or inadequate blood flow to the organs of the body.
The age at which coarctation is detected depends on the severity of the narrowing. In approximately 50 percent of cases of isolated coarctation, the narrowing is severe enough to cause symptoms in the first days of life when the ductus arteriosus closes. When the ductus arteriosus closes, the left ventricle must suddenly pump against much higher resistance which can lead to heart failure. In addition, there is impaired blood flow to the organs beyond the coarctation. Because these newborns are well until the ductus arteriosus closes, symptoms appear rapidly and are often severe.
Coarctation is suspected when the physician is unable to feel pulses in the groin or the legs of an infant. A murmur is sometimes, but not always, present in infants with coarctation. The diagnosis of coarctation is usually made with echocardiography, which can define the anatomy of the aorta and evaluate for other cardiac anomalies.
When a coarctation goes undetected in the newborn period, it may go unrecognized for many years in some cases. Since the narrowing is generally less severe or has progressed more slowly, the left ventricle has had time to thicken (hypertrophy) in order to pump against the narrowing. After infancy, the most frequent findings leading to the detection of coarctation are:
In a critically ill newborn, the goals of management are to improve ventricular function and restore blood flow to the lower body. A continuous intravenous medication, prostaglandin (PGE-1), is used to open the ductus arteriosus (and maintain it in an open state) allowing blood flow to areas beyond the coarctation. It is also often necessary to begin intravenous medications that improve the contraction of the heart. Babies will almost always need to be placed on a ventilator before surgery.
In symptomatic newborns with coarctation, surgical repair is usually done on an urgent basis following initial stabilization. Rarely, an infant will not improve with medical therapy and surgery must proceed before the infant has been stabilized.
There a number of surgical techniques to repair coarctation. The most common repair involves resection (removal) of the narrowed area with reanastamosis (reconnection) of the two ends to each other. Sometimes the resection must be extended towards the arch if there is a longer segment of narrowing. Less commonly, the narrowing may be opened with a patch or a portion of an artery may be used as a flap to expand the area (called a subclavian flap aortoplasty).
Since older children have less severe symptoms, coarctation repair is typically planned electively. Surgical resection is most commonly performed with resection of the narrowed segment and end-to-end reconnection. Occasionally, patching of the aorta may be necessary.
In older children, an alternative to surgery may be catheter-based therapy. In selected cases, the area of narrowing may be dilated with a balloon. Occasionally placement of a mesh-covered stent may be necessary in addition to the balloon dilation to keep the area open. The characteristics of the narrowing and the age of the child are considered in deciding if balloon dilation is an option for treatment.
In order to repair coarctation, clamps must be placed on the aorta, briefly interrupting blood flow to downstream areas. Potential complications of surgery, although uncommon in children, are damage to downstream organs, particularly the kidneys or the spinal cord.
Recurrence of narrowing of the aorta at the area of the repair is possible, even years following treatment. The rate of restenosis is highest among newborns, occurring in almost 20 percent of patients. The rate of recurrent coarctation after surgical repair decreases in older children, approaching zero by age 3 years. While surgery may be necessary for some patients for recurrence, the majority of cases may be managed with balloon dilation.
Another concern after coarctation repair is hypertension (high blood pressure). While this is rarely seen in infants, most older children have unusually high blood pressure immediately following surgery, which is treated with intravenous medication. Frequently, children will be sent home on medication to treat high blood pressure. Although blood pressure will return to normal in many children (allowing medication to be discontinued), long-term or late hypertension may occur, requiring long-term treatment. The chances of having chronic high blood pressure requiring treatment are greater the older a child is at the time of repair. This is likely due to changes that occur in the blood vessels throughout the body in response to the presence of a coarctation.
Follow-up after surgery is important is because approximately 30 percent of patients with coarctation also have a bicuspid aortic valve for which endocarditis prophylaxis should be followed. Such a valve abnormality may lead to problems later in life.