• LSVC to coronary sinus.
  • Left innominate vein is absent in 80 to 90%.
  • Unroofed coronary sinus- no partition between coronary sinus and LA- so LSVC drains through coronary sinus to LA- cyanosis may occur.
  • ASD at site of coronary sinus ostium.

Clinical features

  • Cyanosis may be present.
  • Shunt is usually small-
    • S2 has wide variable split
    • No tricuspid MDM


  • AV canal defect
  • Heterotaxy


  • ASD
    • At site of coronary sinus ostium
    • Difficult to diagnose by TTE; TEE may demonstrate
    • Indirect evidence of ASD like RV volume overload
  • LSVC to LA
    • Suprasternal view shows downward venous flow to left of aorta
    • Contrast into left arm vein shows contrast in LA
  • Combination of RV volume overload with LSVC to LA is the key to the diagnosis even if the ASD as such is difficult to demonstrate.


  • During surgery, avoid damage to AV node which is close by.