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
  • Prevalence in the United States is estimated to be 4.7 per 10,000 live births[1]
  • Accounts for 3% of all congenital heart disease and almost 20% of all cyanotic CHD defects [2]

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

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


References
  1. Improved national prevalence estimates for 18 selected major birth defects--United States, 1999-2001. MMWR Morb Mortal Wkly Rep. 2006;54(51):1301-5.
  2. Reller MD. Prevalence of congenital heart defects in metropolitan Atlanta, 1998-2005. J Pediatr. 2008;153(6):807-13.
  3. Knipe K et al. Cyanotic congenital heart diseases. Radiopaedia. http://radiopaedia.org/articles/cyanotic-congenital-heart-disease
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