Interrupted Aortic Arch (IAA) is a rare and critical congenital heart defect characterized by a complete discontinuity between the aortic arch and the descending aorta. Unlike coarctation, in which the aortic lumen is narrowed, in IAA there is no anatomical connection between the two segments of the aorta, making the ductus arteriosus essential for postnatal survival. It accounts for less than 1% of all congenital heart defects, with an estimated incidence of 2–3 cases per 100,000 live births.
This anomaly leads to a complete hemodynamic interruption of systemic flow to the lower part of the body, which can be temporarily compensated by a patent ductus arteriosus. Once the ductus closes, acute circulatory collapse occurs. IAA is frequently associated with other cardiac malformations, particularly ventricular septal defect (VSD) and transposition of the great arteries, as well as genetic syndromes such as 22q11.2 microdeletion.
The interruption of the aortic arch results from an error in the embryological development of the left fourth branchial arch and the proximal portion of the descending aorta. This process occurs between the fifth and seventh week of gestation and involves the failure of fusion between aortic segments that normally connect the ascending aortic arch with the thoracic descending portion. This leads to a complete disconnection between the two segments, which can occur in three main locations, forming the classic morphological classifications (types A, B, and C according to Celoria and Patton).
Classification
This classification has both hemodynamic and surgical implications.
The pathogenesis of IAA involves an absolute functional dependence on the ductus arteriosus, which ensures the supply of oxygenated blood to the lower body. In the absence of a direct connection between the aortic arch and descending aorta, postnatal systemic flow becomes completely insufficient when the ductus closes physiologically after birth. For this reason, neonatal survival is strictly dependent on early diagnosis and infusion of prostaglandin E1 to maintain ductal patency.
Many cases of IAA are associated with a ventricular septal defect, which allows for a right-to-left shunt and promotes blood mixing at the cardiac level. However, this condition does not compensate for the lack of distal perfusion and leads to rapidly progressive systemic hypoxemia and metabolic acidosis. In complex cases, there may also be coexistence of transposition of the great arteries or truncus arteriosus.
In addition to the definitive embryologic causes, several risk factors, both genetic and environmental, have been identified that increase the likelihood of IAA. Among the most significant:
From a pathophysiological perspective, IAA results in a complete blockade of direct systemic perfusion. In these patients, the descending aorta is perfused retrogradely via the ductus arteriosus. Closure of the ductus leads to a drastic reduction in blood flow to the abdominal organs and lower limbs, with hemodynamic collapse, lactic acidosis, anuria, and signs of multi-organ failure appearing within the first hours of life.
Blood pressure is elevated in the upper limbs and drops sharply in the lower limbs, while oxygen saturation may paradoxically be higher in the foot than in the right hand in rare cases with reverse shunting due to excessive pulmonary resistance. In neonates with an associated VSD, partial blood mixing may slightly delay the clinical picture but does not alter the prognosis without prompt treatment.
The clinical presentation of interrupted aortic arch typically occurs within the first 48–72 hours of life, coinciding with the physiological closure of the ductus arteriosus. Until that point, systemic circulation can be transiently maintained by the patent ductus. Once it closes, the absence of perfusion to the descending aorta leads to rapid progression toward a state of hypoperfusion shock.
In neonates, the presentation is typically acute and dramatic, with signs of progressive systemic compromise.
The most frequent symptoms include:
One of the most suggestive findings is the discrepancy between peripheral pulses: brachial pulses may be palpable, while femoral pulses are absent or markedly attenuated. Blood pressure is typically elevated in the upper limbs and undetectable in the lower limbs. This pressure disparity is a key clue in clinical suspicion.
On auscultation, a holosystolic murmur from an associated ventricular septal defect may be heard, while isolated forms may be surprisingly silent on physical examination.
The presence of a continuous left infraclavicular murmur may reflect a patent ductus arteriosus, whereas a dorsal systolic murmur may suggest the presence of collateral or abnormal flow.
In cases with a large VSD or double outlet right ventricle, the clinical picture may be partially masked for a few days but still evolves toward multi-organ failure if untreated. Coexistence with genetic syndromes such as 22q11.2 microdeletion may be indicated by facial dysmorphisms, thymic hypoplasia, or hypocalcemia from congenital hypoparathyroidism.
Differential diagnosis includes other critical duct-dependent congenital heart diseases, such as severe coarctation, hypoplastic left heart syndrome, and interventricular septal interruption with pulmonary stenosis. Urgent echocardiography allows for precise identification of the aortic arch morphology and confirmation of the diagnosis.
The diagnosis of interrupted aortic arch must be made promptly, as neonatal survival depends on the patency of the ductus arteriosus. Clinical suspicion arises when a term newborn develops signs of hypoperfusion shock within a few days of birth, in the absence of apparent infectious causes, especially if associated with absent femoral pulses and discordant pre- and post-ductal oxygen saturations.
The initial evaluation includes measuring blood pressure in both upper and lower limbs: a significant difference or inability to detect distal pressure is highly suggestive.
Pulse oximetry may show an oxygen saturation gradient between the right hand (pre-ductal) and the foot (post-ductal), although this finding may be absent in the presence of reversed flow or intracardiac mixing.
The electrocardiogram may reveal signs of biventricular hypertrophy or nonspecific patterns, often influenced by associated anomalies.
Chest X-ray typically shows an enlarged cardiac silhouette with increased pulmonary vascular markings in cases with left-to-right shunt or heart failure.
The diagnostic gold standard is transthoracic echocardiography, which enables direct visualization of the arch interruption and the morphology of the epiaortic vessels.
Key echocardiographic findings include:
In cases where echocardiography does not provide a complete anatomical view (e.g., patients with limited acoustic windows or complex anatomy), cardiac magnetic resonance imaging or multislice computed tomography is indicated. Both allow for detailed reconstruction of the aortic arch and epiaortic vessels, which is essential for surgical planning.
Cardiac catheterization is now reserved for cases requiring invasive hemodynamic evaluation or when diagnostic uncertainty remains. Pressure gradient measurement and flow assessment allow characterization of systemic changes secondary to the interruption, but these studies are rarely essential for decision-making.
Once the diagnosis is made, it is crucial to proceed without delay to the pharmacological reopening of the ductus arteriosus through continuous infusion of prostaglandin E1. This intervention restores descending aortic flow and buys valuable time for clinical stabilization and definitive surgical correction planning.
Treatment of interrupted aortic arch constitutes a neonatal emergency. The absolute priority is maintaining ductal patency through continuous infusion of prostaglandin E1, which is essential to ensure distal systemic flow while awaiting definitive repair. Initial hemodynamic stabilization allows the newborn to be prepared for cardiac surgery, which must be performed within the first days of life.
The correction is usually performed in a single stage and includes reconstruction of the aortic arch and closure of any associated intracardiac defects, particularly the ventricular septal defect. The surgical technique is tailored to the patient’s anatomy, the distance between aortic segments, and the presence of hypoplasia or anomalies of the epiaortic vessels.
Surgical options include:
Thanks to advances in perioperative management, post-surgical survival now reaches approximately 80–90%, with better outcomes in patients diagnosed early and repaired in stable clinical conditions. Prognosis is closely linked to ventricular function, birth weight, and the presence of extracardiac malformations or genetic syndromes.
Long-term follow-up is essential and must include monitoring of the aortic arch, blood pressure, ventricular function, and any associated anomalies. Quality of life is good in patients treated promptly, but the complexity of the condition requires continuous specialist care throughout growth.
Without treatment, interrupted aortic arch carries a high mortality rate within the first days of life due to circulatory collapse and multi-organ failure. Closure of the ductus arteriosus results in abrupt interruption of systemic flow, leading to rapidly progressive lactic acidosis, anuria, and tissue hypoxia.
Following surgical correction, both early and late complications may arise. The most common involve possible restenosis of the reconstructed segment and persistent arterial hypertension. Ventricular function must be closely monitored, especially in patients who had preoperative volume overload or complex associated anomalies.
In neonates operated on under critical conditions, the risk of neurological damage is not negligible. Perioperative cerebral hypoperfusion may result in ischemic lesions, with consequences on neurocognitive development. Follow-up should include periodic neurological assessments, particularly in children with genetic risk.
The presence of 22q11.2 microdeletion entails additional challenges, including immune alterations, hypocalcemia, and cognitive or behavioral difficulties. In such cases, a multidisciplinary approach and a comprehensive long-term surveillance plan are required.
Finally, late complications include arrhythmias, aortic dilation, residual stenosis, and in some cases, the need for reintervention. For this reason, every patient operated on for interrupted aortic arch must be followed in specialized centers with expertise in complex congenital heart disease.