Transposition of the great arteries

Background

• Type of cyanotic congenital heart disease
• Aorta arises from the right ventricle and the pulmonary artery from the left ventricle
• Results in two parallel circulations
  • The first sends deoxygenated systemic venous blood to the right atrium and back to the systemic circulation via the right ventricle and aorta
  • The second sends oxygenated pulmonary venous blood to the left atrium and back to the lungs via the left ventricle and pulmonary artery
• Incompatible with life unless there is communication between the two parallel circuits
  • Mixing occurs either intracardiac (patent foramen ovale, VSD or ASD) OR extracardiac connections (patent ductus arteriosus or bronchopulmonary collateral circulation)
• Often associated with other cardiac abnormalities
  • Ventricular septal defects (VSD)
  • Left ventricular outflow tract obstruction (dynamic or anatomical)
  • Mitral and tricuspid valve abnormalities
  • Coronary artery variations
• Prevalence in the United States is estimated to be 4.7 per 10,000 live births
• Accounts for 3% of all congenital heart disease and almost 20% of all cyanotic CHD defects

Clinical Features

• Cyanosis, determined by amount of intercirculatory mixing
• Tachypnea
• Murmurs
  • Pansystolic murmur at lower left sternal border if there is a VSD
  • Systolic ejection murmur along the upper left sternal border in patients with left ventricular outflow obstruction
• Diminished pulses in patients who also have coarctation of the aorta or interruption of the aortic arch

Differential Diagnosis

Congenital Heart Disease Types

• Cyanotic
  • Tetralogy of fallot
  • Total anomalous pulmonary venous return
  • Transposition of the great arteries
  • Tricuspid atresia
  • Truncus arteriosus
  • Ebstein anomaly
  • Hypoplastic left heart syndrome
• Acyanotic
  • AV canal defect
  • Atrial septal defect (ASD)
  • Ventricular septal defect (VSD)
  • Cor triatriatum
  • Patent ductus arteriosus (PDA)
  • Pulmonary/aortic stenosis
  • Coarctation of the aorta
• Differentiation by pulmonary vascularity on CXR
  • Increased pulmonary vascularity
    • Large ASD
    • Large VSD
    • Total anomalous pulmonary venous return
    • Transposition of the great arteries
    • Truncus arteriosus
  • Decreased pulmonary vascularity
    • Tetralogy of fallot
    • Rare heart diseases with pulmonic stenosis

Evaluation

"Egg on side/string" sign

• Echocardiography
• ECG
  • Initial ECG often normal
• CXR
  • Classically with “egg on a string” appearance, thought to be a result of the great arteries forming a narrowed vascular pedicle when transposed
• Cardiac catheterization
  • Remains the gold standard, but seldom required to make the diagnosis

Management

• Stabilization of cardiac and pulmonary function and ensure adequate systemic oxygenation
• Prostaglandin E1
  • Provide sufficient intercirculatory mixing between the two parallel circulations by maintaining patency of the ductus arteriosus
  • Start infusion at 0.05 mcg/kg/min IV and titrate up to 0.1 mcg/kg/min, monitoring for hypotension (and apnea)
  • Maintains the ductus (which completely seals by ~3 wks)
  • Side Effects: Hypotension, Bradycardia, Seizures and Apnea
• Balloon atrial septostomy
  • Performed to stabilize patients with severe hypoxemia due to inadequate mixing between the two parallel circuits
  • Balloon is placed across the atrial septum into the left atrium, inflated and then pulled vigorously back across the septum to produce an ASD
• Surgery, Arterial switch operation
  • In rare instances, atrial switch operation when coronary artery anatomy makes arterial switch infeasible
  • Typically performed within the first two weeks of life
• Most will die within the first year of life without treatment

Disposition

• Admit

See Also

• Congenital heart disease