Transposition of the great arteries

Background

Dextro-transposition of the great arteries.

• 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

Subcostal echo view showing discordant ventriculoarterial connections together with the presence of parallel, rather than crossing, great arteries arising from the ventricles.

Echocardiogram in transposition of the great arteries. This subcostal view shows the left ventricle giving rise to a vessel that bifurcates, which is thus identified as the pulmonary artery. Abbreviations: RA=right atrium, RV=right ventricle, LV=left ventricle, PT=pulmonary trunk, LPA and RPA=left and right pulmonary artery.

• 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