Twin reversed arterial perfusion

A rare complication of monochorionic twin pregnancies

Twin reversed arterial perfusion (TRAP) sequence is a rare complication of monochorionic twin pregnancies, where one twin, known as the "acardiac twin," is severely malformed and lacks a functioning heart. The other twin, referred to as the "pump twin," provides circulation for both twins, leading to significant health risks.

Pathophysiology

In TRAP sequence, the acardiac twin receives blood from the pump twin through abnormal arterial anastomoses in the placenta. This reversed blood flow results in the acardiac twin developing without a heart and often without a head, leading to severe malformations. The pump twin is at risk of heart failure due to the increased cardiac workload.

Diagnosis

TRAP sequence is typically diagnosed through ultrasound imaging, which reveals the presence of an acardiac twin. The acardiac twin may appear as a mass with no cardiac activity, and the pump twin may show signs of hydrops fetalis if heart failure is developing.

Management

Management of TRAP sequence focuses on monitoring the pump twin and may involve interventions to reduce the cardiac load on the pump twin. Options include radiofrequency ablation or laser coagulation of the vessels supplying the acardiac twin. In some cases, early delivery may be necessary.

Prognosis

The prognosis for the pump twin depends on the size of the acardiac twin and the degree of cardiac strain. Early detection and intervention can improve outcomes, but the condition remains high-risk.

Related pages

• Monochorionic twins
• Twin-to-twin transfusion syndrome

References

• Hecher, K., et al. (2001). "Twin reversed arterial perfusion: A systematic review of literature." Prenatal Diagnosis, 21(8), 693-699.
• Lewi, L., et al. (2010). "The outcome of twin reversed arterial perfusion sequence diagnosed in the first trimester." American Journal of Obstetrics and Gynecology, 203(3), 213.e1-213.e4.

An ultrasound image showing an acardiac twin.

A historical depiction of an acardiac twin.