Interrupted aortic arch (IAA) is a serious congenital heart anomaly, often associated with other cardiac abnormalities which make its treatment complex. It is found, in at least one out of four cases, to be associated with a genetic mutation, namely, a deletion of the 22q11 locus, also responsible for the DiGeorge syndrome.
Pathology
IAA is due to the abnormal development of the aortic arch, which connects the proximal ascending and distal descending segments of the aorta. The aorta is the main artery of the body, arising directly from the left ventricle of the heart to supply oxygenated blood throughout the body. The branches of the aorta that supply the head, neck and upper extremities arise from the arch itself, namely, the brachiocephalic artery which divides into the right subclavian and right common carotid arteries; the left common carotid artery, and the left subclavian artery. All later branches arise from the descending aorta.
The Celario-Patton classification of IAA is as follows:
- Type A (35%): the break in continuity occurs after the left subclavian arises from the arch.
- Type B: this is the most common, responsible for 50-60% of cases; often associated with DiGeorge syndrome, and with an aberrant right subclavian artery. The break is between the two left branches of the arch.
- Type C: this is the rarest type (5%), with the break being proximal to the left common carotid artery’s origin.
In each type, the subclavian artery may be aberrant, normal or arise from the ductus arteriosus.
Diagnosis
The child with IAA usually appears normal at birth unless other serious cardiac or extracardiac anomalies are also present. However, symptoms and signs appear early in neonatal life.
Signs and symptoms
Symptoms appearing in early neonatal life include:
- Poor feeding
- Cutting off of feeds due to fatigue and shortness of breath
- Sweating and a cold, clammy skin
- Vomiting because of insufficient circulation to the digestive tract
Clinical signs of this condition include:
- Grayish tinge to the skin or cyanosis
- Lethargy
- Low conscious level
- Poor capillary refill in the legs due to low blood flow
- Absent femoral pulses with normal upper limb pulses, with corresponding differences in the blood pressure between the upper and lower limbs
- Rapid shallow breathing
Tests
There are several diagnostic tests that may be used to guide the treatment of interrupted aortic arch.
A chest X-ray will show cardiomegaly with prominent lung markings, as a result of cardiac failure and pulmonary congestion.
An echocardiogram is usually diagnostic, revealing the precise nature and location of the defect in the aortic arch. Other anomalies are also visualized by the ultrasound imaging. Greater precision if required is achieved with a CT or MRI scan. Imaging also shows the extent of ductus flow and the left ventricular function.
The presence of other anomalies should prompt a whole-body scan for full diagnosis. Chromosomal testing should be done if dysmorphic features, signs of known clinical syndromes, or type B IAA, are present. Tests for 22q11 deletion should always be carried out in the latter.
Management
The baby with IAA usually shows no abnormalities at birth but deteriorates dramatically with the closure of the patent ductus arteriosus. The first aim, therefore, is to keep the ductus patent. This is achieved using continuous prostaglandin E1 infusion.
Hypoxemia and resulting metabolic acidosis need to be corrected as rapidly as possible.
Surgical Reconstruction
Following stabilization of the infant, surgical correction should be carried out early on. The current preference is for one-stage repair with primary reconstruction of the aortic arch. The advantages of a one-stage repair include:
- The need for fewer reoperations
- Avoiding the need of pulmonary artery banding which increases the rate of development of subaortic stenosis, an independent risk factor for death
- Possible avoidance of future reconstructions of the aortic arch
Multi-staged repair is also performed in several centers. It consists of anastomosing the two segments of the aorta initially with pulmonary artery banding to encourage blood flow through the aorta. At the second stage, the ventricular septal defect is corrected and the pulmonary bands removed. Whatever the technique used, induced hypothermia and cardiopulmonary bypass are important in achieving the best outcomes.
Reconstruction of the Aortic Arch
Reconstruction of the aortic arch may employ several methods, including:
- Direct anastomosis of the ascending and descending segments
- Repair by a left carotid artery swing-down
- Anastomosis using an interposed artificial conduit
- Use of a patch for augmentation
Complications
Complications following corrective surgery include:
- Bronchial compression if the tension between the anastomosed segments of the aorta is too great
- Left ventricular outflow tract obstruction
- Restenosis of the reconstructed aortic arch
Lifelong follow-up and prophylactic antibiotics are required in all patients. Successful correction significantly improves the quality of life in survivors. The mortality following surgical correction has fallen considerably but may still be as high as 35% across all institutions. Selected studies have reported mortality rates as low as 10%. The outcome of surgery depends much on surgical experience and skill, as well as the presence of other associated cardiac anomalies. Preoperative renal function plays a major role in predicting the outcome, as does the choice of procedure.
References
Further Reading