Acardiac twin

Acardiac twin

Acardiac twin is a rare condition in pregnancy where one twin develops without certain vital structures, including the heart. This condition is a type of twin reversed arterial perfusion (TRAP) sequence, which is itself a subset of monochorionic twins, where the twins share the same placenta. The acardiac twin is unable to survive independently and is typically dependent on the circulatory system of the co-twin, known as the "pump twin," for blood supply.

Etiology

The exact cause of acardiac twinning is not fully understood, but it is believed to result from abnormalities in the placenta's blood vessels that lead to an abnormal blood flow between the twins. This abnormal circulation causes one twin to receive deoxygenated blood, leading to underdevelopment of essential organs, including the heart.

Pathophysiology

In the TRAP sequence, the pump twin works harder to support the circulation of both itself and the acardiac twin. This increased workload can lead to heart failure in the pump twin if left untreated. The acardiac twin, receiving the majority of its blood supply from the pump twin, develops without a fully functional heart and often other significant abnormalities, including a poorly developed or absent upper body and head.

Diagnosis

Acardiac twinning is usually diagnosed through ultrasound during pregnancy. Characteristics such as the absence of a heartbeat in one twin while observing abnormal blood flow patterns can indicate the presence of an acardiac twin.

Treatment

Treatment options are primarily focused on ensuring the health and survival of the pump twin. In some cases, intervention may be necessary to prevent heart failure in the pump twin. Options include laser surgery to ablate the blood vessels connecting the twins or other procedures to interrupt the abnormal blood flow.

Prognosis

The prognosis for the pump twin can vary widely depending on the severity of the condition and the timing and effectiveness of treatment. Without intervention, there is a high risk of morbidity and mortality for the pump twin due to the added strain on its heart.

See also

• Twin
• Monochorionic twins
• Twin-to-twin transfusion syndrome