Ventriculoarterial discordance (arteries are switched)

• ○
  

  Aorta arises from right ventricle (RV), pulmonary artery (PA) arises from left ventricle (LV)

4-chamber view is normal in TGA: Outflow tract assessment is key to making diagnosis

• ○
  

  Outflow tracts parallel as they exit heart

  
  
• ○
  

  PA arises from LV, bifurcates early

  
  
  
  
  • –
    

    Left ventricular outflow tract obstruction in 25%

  
  
  
  
• ○
  

  Aorta arises from RV, gives rise to arch/head and neck vessels

  
  
  
  
  • –
    

    Coarctation of aorta in 5%

  
  

Ventricular septal defect (VSD) in 40-45%

Double-outlet RV

• ○
  

  Only other diagnosis with parallel outflow tracts

Postnatally TGA is lethal without treatment

• ○
  

  Must detect on prenatal scan for appropriate planning

Never assume vessel from LV is aorta: Verify by showing head and neck branches

Never assume vessel from RV is PA: Verify by showing early division into branch PAs

If parallel outflow tracts are seen

• ○
  

  Identify LV, RV, look for VSD

  
  
• ○
  

  Differentiate aorta from PA

  
  
• ○
  

  Look for outflow tract obstruction

If only 2 vessels visible on 3-vessel view

• ○
  

  Superior vena cava (SVC) + normal-sized vessel → transposition of great arteries

  
  
  
  
  • –
    

    Both great arteries are present but aligned abnormally so not visible on same axial plane

  
  
  
  
• ○
  

  SVC + large vessel → truncus