Interrupted Aortic Arch

Complete loss of luminal continuity between the ascending and descending aorta. The descending aorta is supplied from the pulmonary artery through the ductus arteriosus, so survival after birth depends on a patent ductus. About 1% of congenital heart disease.

• Types by site of interruption: type A (beyond the left subclavian artery, about 30 to 40%), type B (between the left common carotid and left subclavian arteries, about 50 to 70%, the commonest and the type associated with 22q11.2 deletion in about half), and type C (between the innominate and left carotid arteries, less than 5%). Aberrant right subclavian artery coexists with type B in about one third.
• A ventricular septal defect is almost always present (more than 90%), with posterior malalignment of the outlet septum and subaortic narrowing. Other associations: aortopulmonary window, truncus arteriosus, bicuspid aortic valve.
• Physiology: lower body perfusion through the ductus with right to left flow. As the ductus closes (day 2 to 14), the descending aorta loses supply, causing shock, acidosis, renal and bowel ischaemia.
• Untreated, most affected infants die in the first weeks of life.

• A well infant at birth who deteriorates at ductal closure: poor feeding, tachypnoea, lethargy, cool mottled lower body, oliguria, metabolic acidosis, shock.
• Differential cyanosis (lower body bluer than the right hand, in type B the left arm may be bluer too if the left subclavian is distal), weak or absent femoral pulses with a pulse difference between right arm and legs, and a systolic murmur from the ventricular septal defect.
• Hypocalcaemic seizures or tetany from 22q11.2 deletion; cleft palate and facial features.
• Differential diagnosis: coarctation of the aorta (a narrowing, not an interruption), critical aortic stenosis, hypoplastic left heart syndrome, neonatal sepsis, persistent pulmonary hypertension of the newborn, necrotising enterocolitis, and inborn errors of metabolism.
• Complications: necrotising enterocolitis, acute kidney injury, hypocalcaemia, hypoxic injury, left bronchus compression, recurrent arch obstruction after repair, and subaortic stenosis.

• Four limb blood pressure and pre and post-ductal saturations. Arterial blood gas and lactate (metabolic acidosis), urea, creatinine, calcium, glucose, blood culture.
• Echocardiography: suprasternal view shows absent arch continuity, large ventricular septal defect with posterior displacement of the outlet septum, subaortic narrowing, and the ductus feeding the descending aorta; sidedness of the arch and the branch pattern; aortic valve size.
• CT angiography confirms arch anatomy and the aberrant subclavian artery when echocardiography is incomplete, without delaying treatment.
• Fluorescence in situ hybridisation or microarray for 22q11.2 deletion; lymphocyte subsets, immunoglobulins and parathyroid hormone.

• Immediate stabilisation:
  • Alprostadil 0.05 to 0.1 micrograms/kg/min IV to reopen or maintain the ductus; once the ductus is open, reduce to 0.01 to 0.05 micrograms/kg/min. Be ready for apnoea (about 10 to 12%), so intubate for transfer if the infant is small or on higher doses.
  • Avoid supplemental oxygen (it constricts the ductus and increases pulmonary flow at the expense of the lower body); aim for SpO2 of 75 to 85%.
  • Treat acidosis with adequate ventilation and perfusion; sodium bicarbonate 1 mmol/kg IV only for severe acidosis.
  • Inotropes: dopamine 5 to 10 micrograms/kg/min or adrenaline 0.02 to 0.1 micrograms/kg/min; avoid excess pulmonary flow with modest ventilation (PaCO2 of 45 to 55 mmHg is acceptable).
  • Calcium gluconate 10% 0.5 to 1 mL/kg IV slowly for hypocalcaemia; irradiated, cytomegalovirus safe blood products only for suspected 22q11.2 deletion.
  • Monitor urine output, lactate, and signs of necrotising enterocolitis (delay enteral feeds).
• Definitive surgery, within days of diagnosis and when stable:
  • Single stage complete repair through median sternotomy: direct end-to-side anastomosis of the descending aorta to the ascending aorta, division of the ductus, and closure of the ventricular septal defect. Operative mortality about 5 to 15%, with a 5-year survival of 75 to 85%.
  • When the left ventricular outflow tract is severely obstructed (subaortic diameter less than about 3 to 4 mm in a term infant, or aortic annulus too small): a Norwood type or Yasui operation, or arch repair with pulmonary artery banding as a staged strategy.
• Late complications and management:
  • Recurrent arch obstruction (about 10 to 20%): balloon angioplasty, stent, or surgical revision when the arch gradient is 20 mmHg or more with hypertension or ventricular dysfunction.
  • Subaortic or aortic valve obstruction (about 10 to 20%): resection or valve intervention when the peak gradient is 50 mmHg or more or symptoms occur.
  • Left bronchial compression: aortopexy or bronchoscopic assessment.
  • Hypertension: bisoprolol 0.05 to 0.1 mg/kg once daily in children (2.5 to 10 mg in adults), or ramipril 2.5 to 10 mg daily in adults.
• Endocarditis prophylaxis after repair with prosthetic material: amoxicillin 50 mg/kg (maximum 2 g) orally 30 to 60 minutes before dental procedures; clindamycin 20 mg/kg (maximum 600 mg) if allergic to penicillin.
• Special groups:
  • 22q11.2 deletion: immune, endocrine, speech, and neurodevelopmental review; avoid live vaccines until T-cell function is assessed; hypocalcaemia monitoring.
  • Pregnancy: repaired patients with no residual obstruction usually tolerate pregnancy; check the arch, aortic valve and root, left ventricular function, and blood pressure before conception; counsel about 50% recurrence risk if the mother carries a 22q11.2 deletion.
  • Adults: surveillance for aortic aneurysm at the anastomosis, valve disease and hypertension.
• Red flags: absent femoral pulses, collapse at 2 to 14 days, differential cyanosis, severe acidosis, oliguria, hypocalcaemic seizures, abdominal distension with bloody stool.
• Follow up: echocardiography and four limb blood pressure at 1, 3, 6 and 12 months, then every 6 to 12 months; MRI or CT of the arch every 2 to 3 years in adolescence and adulthood; lifelong specialist follow up.