Right Aortic Arch And Double Aortic Arch – Genetics, Diagnosis, Prognosis

Embryology

• Normal anatomy results from persistence of the left 4th arch and regression of the right.
• Right Aortic Arch (RAA): persistence of the right 4th arch with regression of the left.
• Double Aortic Arch (DAA): persistence of both arches, forming a complete vascular ring around trachea and esophagus.

Right Aortic Arch (RAA)

Definition

Aortic arch courses to the right of the trachea.

Subtypes

1. RAA with aberrant left subclavian artery (ALSA)

• Often forms a vascular ring with the ligamentum arteriosum
• Most common subtype

2. RAA with mirror-image branching

• Branching mirrors normal left arch
• Usually no vascular ring
• Often associated with intracardiac CHD

3. RAA with isolated left subclavian artery (rare)

• Strongly associated with 22q11.2 deletion

Prenatal Ultrasound Diagnosis

Three-vessel–trachea (3VT) view

Findings:

• Aortic arch seen to the right of the trachea
• V-shaped configuration with ductus depends on subtype

Subtype clues:

• RAA + left ductus → U-shaped ring (suggests vascular ring)
• RAA + right ductus → mirror-image branching

Associated Cardiac Anomalies (RAA)

• Tetralogy of Fallot (most common)
• Truncus arteriosus
• Pulmonary atresia with VSD
• Ventricular septal defect

CMA is recommended for all prenatally diagnosed RAA, even if isolated.

Prognosis (RAA)

• Isolated RAA, no vascular ring: Excellent, often asymptomatic
• RAA with vascular ring: Possible postnatal feeding or respiratory symptoms
• RAA with CHD: Prognosis driven by cardiac lesion

Most isolated cases have normal neurodevelopment.

Double Aortic Arch (DAA)

Definition

Persistence of both right and left aortic arches, forming a complete vascular ring.

Prenatal Ultrasound Diagnosis

3VT view:

• Trachea encircled by two arches
• Classic “O-shaped” ring around trachea

Genetic

• Lower association with 22q11.2 deletion compared with RAA
• Most cases are sporadic

Postnatal Course and Prognosis (DAA)

• High likelihood of postnatal symptoms:
  • Stridor
  • Recurrent respiratory infections
  • Feeding difficulties
• Symptoms often appear in infancy

Surgical correction (division of the smaller arch) is usually required and is highly effective.

Long-term prognosis after surgery is excellent.

RAA vs DAA

Take-Home Points

• RAA ≠ DAA biologically or prognostically
• 3VT view is the cornerstone of prenatal diagnosis
• 22q11.2 deletion testing is critical for RAA
• Long-term outcomes are generally very good with appropriate follow-up