Interrupted aortic arch (IAA) is a very rare heart defect (affecting 3 per million live births) in which the aorta is not completely developed. There is a gap between the ascending and descending thoracic aorta. IAA can be associated with other more complicated cardiac anomalies; for example, ventricular septal defect (VSD), transposition of the great arteries, truncus arteriosus, aortopulmonary window, single ventricle, aortic valve atresia, right-sided ductus, and double-outlet right ventricle.
According to the Celoria and Patton classification, Interrupted aortic arch can be grouped into three types:
- Type A: The disruption is located distal to the left subclavian artery; this is the second most common disruption represents approximately 13% of the cases.
- Type B: The disruption is located between the left carotid artery and the left subclavian artery; this is the most common anomaly, representing approximately 84% of the cases, and is the classification most often associated with DiGeorge syndrome.
- Type C: The disruption is located between the innominate artery and the left carotid artery; this is a rare type represents approximately 3% of all cases.
The incidence of interrupted aortic arch (IAA) is about 2 cases per 100,000 live births. Nearly all patients with IAA present in the first 2 weeks of life when the ductus arteriosus closes. Most patients present on the first day of life.
During fetal circulation, the ductus arteriosus provides blood to the distal extremities of the fetus and the upper part of the body receives its blood supply from the left ventricle to the aorta. After birth, the pulmonary vascular resistance decreases, promoting the closure of the ductus arteriosus. This leads to the inability of the heart to provide blood to the distal part of the body and produces respiratory distress and cyanosis, leading to cardiogenic shock and death if the necessary measures are not instated in time.
SIGNS AND SYMPTOMS
Signs and symptoms of poor perfusion or congestive heart failure may develop when the ductus arteriosus begins to close, usually within the first day or two of life. The infant may develop weakness, fatigue, poor feeding, rapid breathing, fast heart rate, or 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
Diagnosis of interrupted aortic arch may be suspected based on the symptoms the infant has on presentation. It is then confirmed by an echocardiogram. Once the diagnosis is suspected and confirmed, treatment and surgical intervention are vitally important. The diagnosis can also be made prior to birth via ultrasound. Patients will have a loss of appetite, appear tired and weak, and exhibit rapid breathing and a rapid heart rate. If the condition progresses, the infant may turn pale, feel cold in the lower half of the body, and have a weak pulse due to insufficient blood flow. The pattern of pulse abnormalities is dependent upon the classification; e.g., for type B interrupted aortic arch, the right brachial pulse will be palpable and the left brachial and femoral pulses will be impalpable due to closure of the ductus arteriosus. Rarely, an interrupted aortic arch can be associated with an intracranial aneurysm. Signs of ischemia due to interrupted aortic arch can be separated by the organ system involved
- Liver injury: elevated serum glutamic oxaloacetic transaminase(SGOT) (also known as aspartate transaminase, AST) and lactic acid dehydrogenase (LDH)
- Kidney injury: elevated serum creatinine
- Intestinalinjury: signs of necrotizing enterocolitis, such as bloody stools
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) to help the infant urinate excess fluid
-Administration of inotropic 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
The goal of surgery is to reconnect the aortic arch to create a continuous “tube” and close the ventricular septal defect. Surgery is typically performed urgently but after the infant is stabilized (usually in the first few days of life).
Open-heart surgery will be done to connect the two separate portions of the aorta, close the ventricular septal defect and tie off (ligate) the patent ductus arteriosus.
Failure to treat the condition yields a mortality rate of 90% at a median age of 4 days. Death occurs due to increased blood flow from the left side of the heart (oxygenated blood) to the right side (deoxygenated blood), inducing heart failure; pulmonary edema; and eventual closing of the ductus arteriosus. For an infant with an interrupted aortic arch, a patent (open) ductus arteriosus allows for blood to bypass the “interruption,” without which blood will be unable to reach the lower half of the body. As a result, the kidneys fail and the blood becomes acidic, resulting in death
The most common, early complication of surgery is bleeding, the risk of which can be increased by prematurity, prolonged acidosis prior to surgery, and excessive tension on the anastamosis due to inadequate mobilization of the ascending and descending aorta. Other early complications include damage to the left recurrent laryngeal nerve and the phrenic nerve. Late complications include obstruction of the graft and obstruction of the left main bronchus (which passes underneath the aortic arch).