The aorta is the main blood vessel that carries oxygen-rich blood away from the heart to the organs of the body. After it leaves the heart, it first ascends in the chest to give off blood vessels to the arms and head. Then, it turns downward, forming a semicircular arch, and heads toward the lower half of the body. Interrupted Aortic Arch (IAA) is the absence or discontinuation of a portion of the aortic arch.
There are three types of Interrupted Aortic Arch, and they are classified according to the site of the interruption.
- Type A: the interruption occurs just beyond the left subclavian artery. Approximately 30 percent to 40 percent of the infants with Interrupted Aortic Arch have Type A.
- Type B: the interruption occurs between the left carotid artery and the left subclavian artery. Type B is the most common form of Interrupted Aortic Arch, accounting for about 53 percent of reported cases.
- Type C: the interruption occurs between the innominate artery and the left carotid artery. Type C is the least common form of Interrupted Aortic Arch, accounting for about 4 percent of reported cases.
Interrupted Aortic Arch is thought to be a result of faulty development of the aortic arch system during the fifth to seventh week of fetal development. This defect is almost always associated with a large ventricular septal defect (VSD). Patients with Interrupted Aortic Arch (particularly those with type B) often have a chromosomal abnormality called DiGeorge syndrome. In addition to Interrupted Aortic Arch, patients with DiGeorge syndrome may have problems with low calcium, developmental delay, and immune system abnormalities.
In patients with Interrupted Aortic Arch, oxygen-rich blood from the left side of the heart is not able to reach all areas of the body because of the defect in the aortic arch. An infant with Interrupted Aortic Arch must depend on an alternate way to get adequate blood flow to the lower body.
Normally, a fetus has an extra arterial connection called a ductus arteriosus. The ductus arteriosus is critical to survival in the womb. Shortly after birth, the ductus arteriosus usually closes. If it remains open, it is called a patent ductus arteriosus (or PDA). In a child with Interrupted Aortic Arch, the PDA provides a critical alternate way to get adequate blood flow to the lower body.
While the ductus arteriosus is open, infants may not have noticeable symptoms and may not be diagnosed. As the ductus arteriosus starts to close, however, the infant begins to show signs and symptoms of inadequate blood flow to the area after the interruption. Symptoms may include:
- Poor feeding
- Rapid breathing
- Fast heart rate
- Low oxygen levels, particularly when measured in the legs and feet
This condition can worsen and lead to shock. The infant will then be pale, mottled, and cool. The infant will likely have decreased urine output and poor pulses, especially in the lower extremities. Inadequate blood flow to the body may also result in congestive heart failure.
If a ventricular septal defect is present, blood will be diverted (shunted) from the left side to the right side of the heart. This shunting causes an increase blood flow to the lungs, which leads to congestive heart failure as well.
Once the diagnosis is suspected and confirmed, treatment and surgical intervention are vitally important. Immediate treatment includes the administration of a prostaglandin infusion. Prostaglandin is a medication that is administered intravenously (IV) and keeps the ductus arteriosus open. This allows blood flow to the lower body until surgery is done to re-establish continuity of the aortic arch.
Goals of treatment are aimed at stabilizing and supporting the infant until surgical intervention. Such treatment may include:
- Intubation – endotracheal or “breathing tube” placed in the airway
- Diuretic therapy (water pills) – help the infant urinate excess fluid
- Inotropic medications – medications to help improve the pumping action of the heart
- Monitoring and correction of abnormal blood gases (carbon dioxide and oxygen levels in the blood) and electrolytes (potassium and calcium levels in the blood)
- Administration of nutrition
Open-heart surgery will be done to connect the two separate portions of the aorta, close the ventricular septal defect, and tie off the patent ductus arteriosus. Surgery is typically performed urgently but after the infant is stabilized (usually in the first few days of life). Survival is not possible without surgery.
Complications after Interrupted Aortic Arch repair may include:
- Residual obstruction at the aortic repair site
- The aortic valve or the area below the valve are often small and may not grow, which can result in stenosis (narrowing) months or years following surgery
The risk of complications both early and late following the repair of interrupted aortic arch with ventricular septal defect depends on a number of factors. Risk of surgery is higher if the child has a very small size of the aortic valve region or if the child is significantly ill or unstable before surgery.
Long-term follow-up by the cardiologist to assess growth of the aortic valve region and the reconstructed aortic arch is essential. Reoperation to address further problems with these areas may be needed in 10 to 20 percent of patients. Survival after complete repair of the aortic arch and ventricular septal defect in the newborn period is 90 percent or greater.