Interrupted Aortic Arch (IAA)

Introduction

Interrupted Aortic Arch (IAA) is a rare congenital heart defect characterized by a complete interruption of the aortic arch continuity, preventing normal systemic blood flow. It is a critical condition requiring prompt treatment, as the newborn depends on a patent ductus arteriosus for organ perfusion. This condition is often associated with a ventricular septal defect (VSD) and 22q11 deletion syndrome (DiGeorge syndrome).

Anatomy and Pathophysiology

In IAA, the interruption of the aortic arch prevents blood flow from the aortic root to the systemic arteries, leading to hypoperfusion and metabolic acidosis. The patent ductus arteriosus provides compensatory flow, but its closure rapidly results in cardiogenic shock. IAA is classified based on the site of interruption:

Type A → Interruption distal to the left subclavian artery.
Type B → Interruption between the left common carotid artery and the left subclavian artery (the most common type, often associated with DiGeorge syndrome).
Type C → Interruption proximal to both carotid arteries.

Type B IAA is the most frequent and is often associated with ventricular septal defects.

Epidemiology

IAA accounts for approximately 1% of critical congenital heart defects. In 50-70% of cases, it is associated with 22q11 deletion, which includes immunological abnormalities, hypocalcemia, and craniofacial dysmorphisms.

Signs and Symptoms

Newborns with IAA initially appear normal but rapidly develop signs of hypovolemic shock as the ductus arteriosus closes. Cyanosis and peripheral hypoperfusion are prominent, with absent pulses in the lower limbs. Metabolic acidosis quickly develops, leading to multi-organ failure if not promptly treated.

Diagnosis

IAA can be diagnosed prenatally through fetal echocardiography. After birth, echocardiographic diagnosis confirms the interruption of the aortic arch and the patency of the ductus arteriosus. Electrocardiogram (ECG) may show signs of right ventricular hypertrophy. Genetic analysis is recommended to assess for 22q11 deletion syndrome.

Treatment

IAA is a cardiac emergency requiring immediate intervention. Initial management includes the administration of prostaglandins (PGE1) to maintain ductal patency and ensure minimal systemic blood flow. Surgery is the only definitive treatment and involves:

Aortic arch reconstruction → Anastomosis between the interrupted segments to restore aortic continuity.
Closure of the ventricular septal defect → Necessary in cases associated with VSD.
Management of associated anomalies → Correction of immunological and metabolic abnormalities, if present.

In neonates with severe comorbidities, a palliative approach may be required before definitive repair.

Prognosis

Without treatment, mortality reaches 100% within the first month. After surgical correction, long-term survival is possible, but patients require continuous follow-up to monitor aortic growth and the risk of hypertension.

References

Presbitero P. et al. Interrupted Aortic Arch: Natural History and Operative Results. J Thorac Cardiovasc Surg. 1987;93(3):399-407.
Freedom R.M. et al. Interrupted Aortic Arch: A Review of 50 Cases. J Am Coll Cardiol. 1983;1(3):539-547.
McCrindle B.W. et al. Risk Factors and Outcomes of Interrupted Aortic Arch: A Congenital Heart Surgeons Society Study. J Am Coll Cardiol. 2005;46(1):127-133.