Twin Reversed Arterial Perfusion

Also known as: acardiac twinning, TRAP sequence, TRAPS, TRAP syndrome.

What is twin reversed arterial perfusion?

Twin reversed arterial perfusion is a rare disorder that sometimes occurs in identical twins that share a placenta, where one twin has a poor functioning cardiac system receives blood from the healthy twin (pump twin). The term “Reversed arterial perfusion” is used because blood flows in the opposite direction from that which is normal. The amount of work the “pump twin’s” heart does is tremendously increased (because it's doing all the work of two) frequently causing it to “fail”.

What causes twin reversed arterial perfusion? 

The cause is unknown, however as it only occurs in identical twins that share a placenta it is thought that a combination of an abnormal heart (or no heart- acardic), (and/or no head-
acephalic) in one twin, and the joining of vessels during fetal development results in mixing of the two blood vessel systems. The condition does not appear to run in families.

What are the signs/symptoms of twin reversed arterial perfusion? 

The main risks of TRAP sequence occur within the womb to the healthy baby that is supplying blood to the undeveloped baby. Increased amniotic fluid, and signs of heart failure and death are possibilities for the healthy fetus.

What are twin reversed arterial perfusion care options?

Careful monitoring of the normal twin during pregnancy is important to detect early heart failure. Should signs occur, treatments may include early delivery (depending on the gestational age of the babies), stopping the blood flow to the abnormal twin by in utero radiofrequency ablation (clotting the abnormal blood vessels), or surgery in utero to cut the blood supply to the abnormal fetus. 

Reviewed by: Jack Wolfsdorf, MD, FAAP

This page was last updated on: 3/23/2018 2:06:29 PM


Anthony Rossi, MD of Nicklaus Children's Hospital is the Chief of Cardiovascular Medicine with The Heart Program.

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