Complete right heart flow reversal: pathognomonic recipient twin circular shunt in twin-twin transfusion syndrome

Fetal and Neonatal Circulatory Disorders in Twin to Twin Transfusion Syndrome (The Secondary Publication)

Twin to twin transfusion syndrome (TTTS) is a major complication of monochorionic diamniotic (MD) twins, and its onset is known to be associated with placental vascular anastomoses and blood flow imbalance. In a typical case of TTTS, the recipient develops polyhydramnios, weight gain, cardiomegaly and hydrops fetalis in the uterus. In contrast, the donor develops oligohydramnios and intrauterine growth restriction. Recently, the significance of the renin-angiotensin-aldosterone system (RAAS) that transfers from the donor to the recipient has attracted interest in the fetal circulation of TTTS. The donor has decreased renal blood flow due to decreased circulating blood volume. For this reason, the secretion of RAAS hormones is augmented in the fetal kidneys of the donor. In TTTS, these RAAS hormones from the donor transfer to the recipient through the anastomosed vessels. In addition to excess preload, the recipient heart is exposed to excess afterload due to systemic vasoconstriction through RAAS hormones. Commonly occurring complications in the recipient include myocardial hypertrophy, atrioventricular valve regurgitation, and pulmonary valve stenosis or pulmonary atresia. Fetoscopic laser photocoagulation (FLP) has been introduced recently because neither mortality nor neurological morbidity have been satisfactorily improved with conventional treatment. FLP is a curative method that may improve the prognosis of TTTS. In Japan, this procedure has been performed frequently, and positive neurological outcomes have been achieved.

Long-term outcomes for monochorionic twins after laser therapy in twin-to-twin transfusion syndrome

Twin-to-twin transfusion syndrome typically occurs in the second trimester in 10-15% of monochorionic twin pregnancies. Vascular anastomoses of monochorionic placentae are the underlying cause of the development of the syndrome. If a blood flow imbalance occurs, one fetus becomes the so-called donor twin and the other the recipient. If untreated, perinatal mortality is 80-90%. Fetoscopic laser coagulation of the vascular anastomoses destroys the cause of the syndrome and leads to dual twin survival rates of around 70% and more than 90% of pregnancies with at least one survivor. However, unequal placental sharing, intrauterine death, and severe prematurity are still limiting factors for further improvement of survival rates and decreases in long-term morbidity. Prematurity and neurodevelopmental impairment affect the donor and recipient twins, whereas cardiovascular failure and obstruction of the right ventricular outflow tract are typical complications of recipients, which can lead to long-term morbidity. In this Review, we summarise the literature on follow-up data for survivors of twin-to-twin-transfusion syndrome after laser therapy, including neurodevelopmental outcomes, cardiovascular outcomes, growth, renal function, and ischaemic events, as well as the potential effects of intrauterine programming on later life.

Recipient Twin Circular Shunt Physiology Before Fetal Laser Surgery: Survival and Risks for Postnatal Right Ventricular Outflow Tract Obstruction

OBJECTIVES

To evaluate risk for congenital heart disease (CHD) in recipient twins with circular shunt physiology (CSP).

METHODS

This prospective study enrolled twin-twin transfusion syndrome (TTTS) cases from 2006 to 2015. Fetal echocardiography (FE) was performed before laser surgery when cardiac involvement was suspected. Diagnosis of recipient twin CSP required tricuspid and pulmonary regurgitation, right ventricular dysfunction, and flow reversal in the ductus arteriosus. Outcomes were assessed at 30 days after birth.

RESULTS

Of the 496 TTTS pregnancies, 20 (4%) met the criteria for CSP. Among those born alive, who had documented cardiac outcomes (n = 457), patients with CSP were more likely to have CHD, specifically right ventricular outflow tract obstruction (5 of 18 [27.8%] versus 22 of 439 [5.0%], odd ratio [OR] 7.29, 95% confidence interval [CI] 2.05-24.72, P = .0025). Of the recipient twins with preoperative FE (n = 259, 52%) who were born alive and had documented cardiac outcomes (n = 242), those with CSP were still more likely to have right ventricular outflow tract obstruction (5 of 18 [27.8%] versus 14 of 224 [6.3%], OR 5.77, CI 1.54-20.92, P = .0077). With both analyses, twins with CSP had higher Quintero stage, but similar patient characteristics and 30-day mortality compared with those without CSP. Subgroup analyses of the CSP cohort identified no differences in preoperative characteristics or FE findings predictive of CHD.

CONCLUSIONS

Recipient twins with preoperative CSP were at increased risk for postnatal right ventricular outflow tract obstruction, but appeared to have comparable survival after fetal laser surgery despite these dramatic pathophysiological prenatal findings. Preoperative FE in TTTS remains important for prediction of postnatal CHD.

Blood pressure evaluation in children treated with laser surgery for twin-twin transfusion syndrome at 2-year follow-up

OBJECTIVE

Twin survivors of twin-twin transfusion syndrome (TTTS) may be at risk for early onset of cardiovascular disease. The aim of this study was to determine prevalence and risk factors for elevated blood pressure (BP) among children treated with selective laser photocoagulation of communicating vessels.

STUDY DESIGN

Data were prospectively collected from surviving children treated for TTTS with laser surgery from 2008 through 2010. Systolic BP (SBP) and diastolic BP (DBP) were obtained from 91 child survivors at age 24 months (±6 weeks) and evaluated based on age, sex, and height percentile. BP percentiles were calculated for each patient and categorized as normal (<95%) or abnormal (>95%). Clinical variables were evaluated using multilevel regression models to evaluate risk factors for elevated BP.

RESULTS

BP was categorized as normal in 38% and abnormal in 62% of twin survivors based on percentile for sex, age, and height; a comparable distribution was found for DBP elevation. There were no differences between donor and recipient twins for absolute SBP and DBP or BP classification. In a multivariate analysis, significant risk factors for higher SBP included prematurity (β -0.54; 95% confidence interval [CI], -0.99 to -0.09; P = .02), higher weight percentile (β 0.24; 95% CI, 0.05-0.42; P = .01), and presence of cardiac disease (β 0.50; 95% CI, 0.10-0.89; P = .01). Prematurity was also a significant risk for abnormal DBP (odds ratio, 0.89; 95% CI, 0.80-1.00; P = .05).

CONCLUSION

Child survivors of TTTS had elevated SBP and DBP measurements at 2 years of age, with no differences seen between former donor and recipient twins. Prematurity may be a risk factor for elevated BP measurements in this population. Future studies are warranted to ascertain whether these cardiovascular findings persist over time.

The Fetal Heart in Twin-to-Twin Transfusion Syndrome

Twin-to-twin transfusion syndrome is a severe complication occurring in 10% of monochorionic twin pregnancies. The disease is usually explained as due to an intrauterine imbalance in intertwin blood exchange, which leads to a volume depleted-donor twin and an overfilled recipient twin. The recipient has signs of cardiac dysfunction, which can be measured using echocardiography or blood and amniotic fluid derived biomarkers. Whereas cardiac dysfunction typically progresses in pregnancies treated with amniodrainage, it usually disappears within a few weeks after fetoscopic laser coagulation of the connecting intertwin anastomoses. Nevertheless, recipients remain at a increased risk of pulmonary stenosis. In this paper, we summarize the cardiac alterations in twin-to-twin transfusion syndrome, describe the changes seen after fetal therapy, list the newly proposed staging systems based on fetal cardiac function, and make recommendations about the use of fetal echocardiography in the evaluation and followup of pregnancies complicated by twin-to-twin transfusion syndrome.