Congenital heart disease with 4 components

• ○
  

  Right ventricular outflow tract (RVOT) obstruction

  
  
• ○
  

  Right ventricular hypertrophy

  
  
• ○
  

  Ventricular septal defect (VSD)

  
  
• ○
  

  Aorta overrides or straddles VSD

95% of affected fetuses have normal 4-chamber view

Outflow tract assessment is key to making diagnosis

Normal cardiac axis is 35-45°

• ○
  

  Abnormal axis may be only sign of conotruncal heart disease on 4-chamber view

RVOT obstruction

• ○
  

  Anterior deviation of infundibulum (part of interventricular septum) at level of outflow tracts

  
  
• ○
  

  Pulmonary valve (PV) usually abnormal

  
  
• ○
  

  Pulmonary artery (PA) small with stenotic PV

  
  
• ○
  

  PA and branches markedly enlarged if absent pulmonary valve (APV)

  
  
  
  
  • –
    

    Back and forth flow across PV seen with color Doppler

  
  

Aorta overrides large VSD

Careful evaluation of outflows in any fetus with abnormal cardiac axis

Use 3-vessel view to compare sizes of aorta and PA

• ○
  

  Aorta is large in tetralogy of Fallot (ToF)

  
  
• ○
  

  PA is huge in ToF with APV

Look for other abnormalities

• ○
  

  ToF associated with trisomies 21,18,13

  
  
• ○
  

  Look for fetal thymus (absence suggests 22q11 deletion syndrome)

  
  
• ○
  

  ToF may be component of syndromes such as VACTERL

  
  
  
  
  • –
    

    Vertebral, anorectal, cardiac, tracheoesophageal, renal, limb anomalies