Fetal cardiovascular alterations in twin-to-twin transfusion syndrome

Abstract

Twin-to-twin transfusion syndrome (TTTS) is the consequence of vascular anastomoses of the shared placenta of monochorionic twin pregnancies. Both circulating inter-twin blood flow and vasoactive mediators imbalance cause hypovolemia in the donor and hypervolemia in the recipient fetus. If left untreated, TTTS has a high perinatal mortality rate and adverse long-term outcomes mainly cardiovascular and neurological.
 The recipient has cardiovascular changes including atrioventricular valve regurgitation, diastolic dysfunction and pulmonary stenosis/atresia. The maladaptive response to vascular changes determines a constant decreased blood flow in the donor that permanently modifies the arterial structure leading to postnatal alterations in the vascular system. Fetoscopic LASER surgery of placental vascular anastomoses may disrupt the underlying pathophysiology and improves cardiovascular function with normalization of systolic and diastolic function within weeks after treatment.
 The impact of cardiovascular changes is relevant for the safety of the management of a TTTS case. The improvement of the perinatal survival after intrauterine surgery leads to viable infants with the longer-term sequelae. Therefore accurate quantification of cardiovascular involvement is essential for clinicians for pregnancy management but also for patient counseling about the potential treatment options the outcome.

Ultrasonographic Diagnosis of Twin-to-Twin Transfusion Syndrome

“…Donor fetus sends blood to recipient fetus, increasing transport and amount of fluids through the placenta to recipient fetus who is unable to handle fluid overload. 19…”

“…In addition, absence of a reflux wave “A” in ductus venosus and an increase in resistance index in umbilical vein are characteristic. 19 Other symptoms derived from hyper and hypovolemia are factors that allow evaluating severity of condition.…”

“…This is not a specific feature of TTTS but an indicator that demonstrates chronic course of disease. 19 In cases with a rapid and acute evolution, the period between hypoxia and intrauterine death is so short that alteration of fetal growth is not evident when performing biometric measurements. 21,22 When disappear mechanisms apply to reduce effects of anemia and hypoxia, damage to endothelium of fetal blood vessels occurs, leading to increased endothelial permeability with passage of fluids to interstitial space.…”

Incidence, prognosis, and perinatal outcomes of and risk factors for severe twin–twin transfusion syndrome with right ventricular outflow tract obstruction in the recipient twin after fetoscopic laser photocoagulation

“…To compensate for the hypovolemia, the donor twin secretes vasoactive mediators, such as endothelin I and renin, which circulate to the recipient twin through intertwin anastomoses; the vasoactive substances can cause polyhydramnios, cardiomyopathy, and atrioventricular valve regurgitation in the recipient twin [ 3 – 5 ]. In 70% of TTTS cases, the recipient twin demonstrates echocardiographic signs of cardiovascular complications at the time of diagnosis [ 6 , 7 ].…”

“…Right ventricular outlet obstruction (RVOTO), such as in pulmonary stenosis (PS) and pulmonary atresia (PA), is the most prevalent form of congenital heart disease, with a reported incidence of 6.7%–12.9% in recipient twins [ 10 – 13 ]. This higher risk exists because recipient twins have high risks of right heart dysfunction, cardiomegaly, and tricuspid valve regurgitation, which can cause the flow through the pulmonary valve to decrease, potentially leading to narrowing and stenosis of the fetal pulmonary valve of the recipient twin [ 6 ]. The etiology of the higher incidence of cardiomyopathy and the lower pulmonary valve flow in the recipient twin compared with the donor twin has been hypothesized as being the result of differing levels of renin–angiotensin activity between the recipient and donor twins [ 14 ].…”