What is Type B interrupted aortic arch?

Type B Interrupted Aortic Arch

Type B interrupted aortic arch is a rare congenital anomaly characterized by complete anatomical discontinuity between the left common carotid artery and the left subclavian artery, representing the most common form of interrupted aortic arch (approximately 67% of cases). 1

Anatomical Classification of Interrupted Aortic Arch

• Type B interrupted aortic arch occurs when there is complete luminal and anatomical interruption between the left common carotid artery and the left subclavian artery 1, 2
• Type A interruption occurs distal to the left subclavian artery (approximately 30% of cases) 1
• Type C interruption, the rarest form (approximately 3% of cases), occurs between the innominate artery and left common carotid artery 1

Epidemiology and Clinical Significance

• Interrupted aortic arch represents approximately 1% of all congenital heart defects, occurring in approximately 3 per million live births 1, 3
• Over 97% of cases have associated cardiac anomalies, complicating treatment 1
• Without treatment, the median age at death is approximately 10 days, making this condition a neonatal surgical emergency 1
• Type B interrupted aortic arch is strongly associated with 22q11.2 deletion syndrome (DiGeorge syndrome) 4

Associated Cardiac Anomalies

• Common associated defects include:
  • Ventricular septal defects 3
  • Patent ductus arteriosus 3
  • Bicuspid aortic valve 3
  • Tetralogy of Fallot with associated anomalies 4
  • Truncus arteriosus 2
• Subaortic stenosis is frequently observed in patients with ventriculoarterial concordance 2

Diagnosis

• Physical examination may reveal peripheral pulse inequality due to ductal constriction, though this finding may be absent or transient 2
• Cross-sectional echocardiography provides accurate non-invasive diagnosis, showing:
  • Ascending aorta terminating at the left carotid artery 2
  • Ductus continuing smoothly into the descending aorta 2
  • No vestige of an aortic arch linking ascending and descending portions 2
• CT angiography (CTA) is useful for detailed morphologic evaluation of the interruption and collateral circulation 3
• Cardiovascular magnetic resonance (CMR) imaging may be used for follow-up assessment 4

Management

• Neonatal management includes:
  • Treatment for biventricular failure 1
  • Prostaglandin E1 (PGE1) infusion to maintain ductal patency 1, 2
  • Surgical correction as soon as feasible 1
• Surgical repair techniques include:
  • Direct aortic-to-aortic anastomosis bridging the gap 1
  • "Turndown" or "turnup" of one of the arch vessels to the aorta across the gap 1
  • Bypass of the interruption with graft material 1
  • Extra-anatomic repair with Dacron grafts between ascending and descending portions of the thoracic aorta 5

Rare Adult Presentation

• Extremely rare cases of adults with unrepaired interrupted aortic arch have been reported 5, 3
• Adult cases typically present with:
  • Hypertension 3
  • Lower extremity edema 3
  • Extensive collateral circulation that has developed over time 3
• CTA is particularly valuable for evaluating collateral circulation in adult cases 3

Genetic Considerations

• Testing for 22q11.2 deletion is recommended for all infants with interrupted aortic arch type B, regardless of the presence of extracardiac features 4
• Genetic counseling is important as affected individuals have a 50% chance of having a child with 22q11.2 deletion syndrome in each pregnancy 4