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Interrupted aortic arch (IAA) refers to a rare but very serious congenital heart defect in which there is a gap between the ascending and descending segments of the aorta, namely, in the arch of the aorta. In 97 of every 100 infants born with this condition, a ventricular septal defect is also present.
Interrupted aortic arch is caused by the defective development of the aorta during early fetal life, probably within the first 5-7 weeks. It accounts for less than 2% of congenital heart anomalies.
Other abnormalities may be associated with this condition. In type B IAA, which accounts for 60% of cases, the break in continuity is between the origin of the left common carotid and the left subclavian artery.
The DiGeorge syndrome, which is associated with deletion of the chromosome 22q11 locus, is found in patients with a type B interrupted aortic arch. It consists of conotruncal defects, T-lymphocyte defects resulting in immunodeficiency, hypocalcemia and with facial anomalies. The association is especially strong when the descending aorta is on the right side. Type B is also found to occur with an aberrant right subclavian artery as well.
The same deletion is found in 50% of type B patients without the typical DiGeorge phenotypic features. All cases of type B IAA should be tested for this mutation.
Trisomy 13 and 18 have also been found to be associated with IAA. Other anomalies found to occur alongside this condition include:
Infants with IAA cannot pump blood through the aorta, and therefore are born suffering from poor systemic supply in the lower part of the body. The upper body receives oxygenated blood through the proximal aortic branches, while the lower part of the body depends upon the flow through the ductus arteriosus to receive desaturated blood. When the ductus closes, within a few days of birth, the circulation to the lower body is cut off, plunging the infant into shock and metabolic acidosis.
Most infants with IAA need emergency neonatal resuscitation and treatment for hypoxemia. In other cases, they may present with:
Signs of a ventricular or atrial septal defect may be present in most of these infants. The ventricular septal defect is beneficial in some of these babies, because it shunts blood from the left side of the heart to the right side, allowing oxygenated blood to reach some parts of the body through the ductus arteriosus which is still open.
Signs and symptoms of associated anomalies may also be picked up, such as the typical facial signs of DiGeorge syndrome.