Insights into the pathophysiology of twin–twin transfusion syndrome

Abstract

Twin-twin transfusion syndrome (TTTS) is attributed to trans-anastomotic transfusion between twins. Anastomoses are ubiquitous in monochorionic (MC) placentae, yet TTTS develops in only 15%. Although ex vivo and in vivo studies fail to identify a unique anastomotic signature, TTTS placentae are typically associated with an imbalance in unidirectional arteriovenous anastomoses with absent bidirectional anastomoses. Doppler detection of an artery-artery anastomosis reduces the chance of TTTS, whereas, in those that develop the disease, it improves stage-independent survival. Selective laser is often curative, but an increasingly recognized risk of persistent or reverse TTTS may be attributable to atypical arteriovenous anastomoses not identifiable from the chorionic plate. Simple dysvolaemia fails to explain several phenotypic features, including haematological concordancy, recipient hypertension, and reversibly absent end diastolic flow in the donor. The renin-angiotensin system is upregulated in the donor and downregulated in the recipient's kidneys, while paradoxically raised renin levels in the recipient may contribute to raised afterload along with endothelin. Although research is limited in humans by therapy and the lack of a suitable experimental model, further studies of placental and vascular pathophysiology may not only refine current treatment modalities but may also, in addition, suggest further avenues for downstream management such as genetic predisposition testing or pharmacological intervention.

Prematurity and twinning

“…The diagnosis usually relies on ultrasound documenting the simultaneous presence of a foetus with an increased bladder size and polyhydramnios while oligohydramnios will be detected in the co-twin [22]. MR imaging revealed persistently small measurements in the donor cerebrum and cerebellum in comparison with their recipient co-twin and healthy control foetuses [23].…”

Altered Fetal Cerebral and Cerebellar Development in Twin-Twin Transfusion Syndrome

“…2 In TTTS, disproportionate intertwin transfusion via placental anastomoses causes circulatory depletion in 1 twin (donor) and overload in the other (recipient). 3 This cardiovascular instability may trigger further systemic changes that result in multiple organ injury, including the brain, in both twins in utero during the second and third trimesters. In twins, TTTS is a significant cause of cerebral palsy (motor disability) and cognitive and behavioral disabilities 4,5 and is a major cause of prematurity.…”

Speckle Tracking-Derived Myocardial Tissue Deformation Imaging in Twin-Twin Transfusion Syndrome: Differences in Strain and Strain Rate between Donor and Recipient Twins

“…As the donor experiences volume depletion, vasoactive mediators are released to constrict the vasculature and maintain perfusion. Through intertwin vascular connections, these vasoconstrictive agents cross into the recipient circulation, which in combination with the blood volume transferred produces a substantial increase in cardiac preload and afterload [3]. Alternatively, it has been proposed that the placenta itself may play a role in the expression of vasoactive mediators, which may also influence differential loading conditions for the twins [4].…”