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

Cardiac adaptation and malformation in twin-twin transfusion syndrome and selective fetal growth restriction: A systematic review

OBJECTIVES

This systematic review explores cardiac adaptation in monochorionic (MC) twins with twin-twin transfusion syndrome (TTTS) or selective fetal growth restriction (sFGR) and assesses the risk of congenital heart defects (CHDs).

METHODS

Adhering to PRISMA guidelines, 63 studies were reviewed (49 on cardiac adaptation, 13 on CHD, one on both). A narrative synthesis of cardiac adaptation patterns was performed. Additionally, a meta-analysis compared the livebirth prevalence of CHD in TTTS and sFGR against uncomplicated MC twins.

RESULTS

In TTTS recipients, cardiac function may be impaired for diastolic, systolic, as well as global functions, while in donors, cardiac function is generally preserved. In sFGR, large twins may show hypertrophic cardiomyopathy, and small twins may show impaired systolic function. Co-occurrence of TTTS and sFGR magnifies cardiac impact but is often underreported. Meta-analysis for CHD prevalence revealed a relative risk ratio of 3.5 (95% CI: 2.5-4.9) for TTTS and 2.2 (95%CI: 1.3-3.5) for sFGR compared with uncomplicated MC twins.

CONCLUSIONS

This study highlights the well-documented cardiac adaptation in TTTS, contrasting with limited understanding in sFGR. Elevated CHD risks were observed in both conditions. Enhanced cardiovascular surveillance is warranted in complicated MC twin pregnancies. Future research should explore cardiac adaptation in sFGR and its long-term consequences.

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

Background

Right ventricular outflow tract obstruction (RVOTO) is the most frequently encountered congenital heart disease in patients with twin –twin transfusion syndrome (TTTS) and is especially prevalent in the recipient twin. In this retrospective study, we evaluated the incidence, prognosis, postnatal management, and perinatal outcomes of and risk factors for RVOTO in the recipient twin in severe TTTS cases which diagnosed before 26 weeks after fetoscopic laser photocoagulation (FLP) at a single center in Taiwan.

Methods

RVOTO was diagnosed using fetal or postnatal echocardiography. The fetal outcomes evaluated were perinatal survival rate, neonatal brain image anomalies rate, gestational age at delivery, and birth weight.

Results

Total 187 severe TTTS cases were included; 14 (7.49%) had a recipient twin with RVOTO (12 cases of pulmonary stenosis and 2 of pulmonary atresia). Of these 14 cases, 3 (21.4%) demonstrated improvements in outflow obstruction after FLP, and 11 (78.6%) resulted in perinatal survival. Of the 11 survivors, 5 (45.5%) received transcatheter balloon valvuloplasty to alleviate the RVOTO. The perinatal survival rate, gestational age at delivery, neonatal brain image anomaly rate, and birth weights did not significantly differ between the groups in which the recipient twin had versus did not have RVOTO. Generally, the recipient twin had RVOTO received FLP at a younger gestational age (in weeks; 19.3 ± 2.4 vs. 20.7 ± 2.6, p = 0.048) and had a higher percentage of cases at Quintero stage IV (50.0% vs. 12.1%, p < 0.001) than those in which the recipient twin did not have with RVOTO. Using logistic regression, we discovered that FLP at a younger gestational age (p = 0.046, odds ratio = 0.779) and TTTS at Quintero stage IV (p = 0.001, odds ratio = 7.206) were risk factors for the recipient twin developing RVOTO after FLP in severe TTTS cases.

Conclusions

The post-FLP perinatal outcomes of cases of severe TTTS in which the recipient twin had versus did not have RVOTO were comparable in this study, which may have been due to the similar gestational ages at delivery and strong influence of high Quintero stages (stages III and IV).

Management of atypical cases of twin-to-twin transfusion syndrome

Up to 20% of monochorionic diamniotic twin pregnancies can be complicated with twin-to-twin transfusion syndrome (TTTS). This complication is diagnosed by ultrasound demonstrating amniotic fluid discordance between both amniotic sacs, with polyhydramnios in the recipient's sac and oligohydramnios in the donor's, secondary to an imbalance in blood volume exchange between twins. Ultrasound evaluation of the amniotic fluid volume, bladder filling, and assessment of fetal Doppler parameters provide the basis for classification of TTTS, allowing severity assessment. The Quintero's staging system provides a standardized prenatal estimate on the risk of intrauterine fetal demise of one or both twins and the need for fetoscopic laser coagulation of placental vascular anastomoses or delivery depending on the gestational age. However, a proportion of TTTS cases may present without a linear progressive deterioration and no ultrasound signs of preceding staging, in rare situations, they arise even without amniotic fluid discordance. Thus, these unusual clinical presentations of TTTS have long been grouped into the category of atypical TTTS. In this review, we show the clues for diagnosis and management of different atypical cases of TTTS highlighting their underlying mechanism to improve the clinical understanding of such atypical situations, avoid misdiagnosis of TTTS, and allow a timely referral to a fetoscopic center.

Umbilical Artery Doppler Patterns and Right Ventricular Outflow Abnormalities in Twin-Twin Transfusion Syndrome

OBJECTIVES

To evaluate the association of abnormal Doppler velocimetric patterns in the umbilical arteries (UAs) and right ventricular outflow tract abnormalities (RVOTAs) in twin- twin transfusion syndrome (TTTS) cases.

METHODS

This retrospective study involved women who had laser surgery for TTTS between January 2012 and May 2018 at a single institution. The prevalence of an RVOTA in either twin was compared among TTTS cases in which both twins had positive end-diastolic flow (EDF) in the UA and those in which either twin had intermittent or persistent absent/reversed UA EDF. Nonparametric tests were used for comparisons. Logistic regression was performed to identify variables associated with an RVOTA in either twin, adjusted for moderate or severe tricuspid regurgitation, right ventricular hypertrophy, right ventricular systolic or diastolic dysfunction, the Quintero stage, and other confounders. P < .05 was considered significant.

RESULTS

A total of 126 consecutive TTTS cases were included. Right ventricular outflow tract abnormalities were seen in 8.7% (11of 126) of cases, all in recipient twins. Significant differences in the rate of RVOTAs in the recipient twin were seen between TTTS cases with intermittent absent/reversed UA EDF and those with positive UA EDF (26.9% [7 of 26] versus 3.7% [3 of 82]; P = .002]. However, no significant differences were noted among the other study groups. Intermittent absent/reversed UA EDF was associated with a significantly increased risk for an RVOTA (adjusted odds ratio, 20.6 [95% confidence interval, 3.1-138]; P = .002) after adjusting for confounders.

CONCLUSIONS

Intermittent changes in vascular impedance to UA flow may contribute to the pathogenesis of acquired right-sided cardiac lesions in the recipient twin affected with TTTS.

Evaluation of cardiac function in the recipient twin in successfully treated twin-to-twin transfusion syndrome using a novel fetal speckle-tracking analysis

INTRODUCTION

This study was designed to evaluate ventricular size, shape, and function in recipient twins following laser therapy for twin-twin transfusion syndrome (TTTS), using novel speckle-tracking techniques.

METHODS

This retrospective study enrolled patients that underwent fetal laser surgery for TTTS and had fetal echocardiograms (FE) performed pre- and post-operatively (op), with adequate resolution in the 4-chamber view for analysis, using a speckle-tracking software, to compute the size, shape, and function of both the right (RV) and left (LV) ventricles. Values were indexed to published normal values. Pre- and post-laser Z-score values for each of the measurements were compared using the Student's t-test, with significance defined as P < 0.05.

RESULTS

Fifteen TTTS candidate pregnancies that underwent laser therapy between 2010 and 2017, with adequate pre- and post-op FE, were selected for the analysis. Post-op FE at 28.5 ± 8.3 days showed a significant decrease in RV base dimension, increased LV base dimension, and improvements in many functional measurements: LV global and free wall strain, LV fractional area change, LV basal-apical fractional change, and LV and RV 24-segment fractional shortening (FS) of the basal segments.

CONCLUSIONS

Cardiac remodeling, following laser surgery in TTTS recipient twins, was demonstrated in the basal portion of both the RV and LV with improved biventricular function.

Acquired right ventricular outflow tract obstruction in twin-to-twin transfusion syndrome; a prospective longitudinal study

OBJECTIVE

The pathophysiology of right ventricular outflow tract obstruction (RVOTO) in twin-to-twin transfusion syndrome (TTTS) recipients is incompletely understood. We aimed to investigate the development and spectrum of RVOTO in TTTS recipients.

METHODS

A prospective longitudinal cohort study was conducted between 2015 and 2017. Echocardiographic assessment was performed in recipients from TTTS diagnosis until the neonatal period.

RESULTS

Prenatal RVOTO, defined as abnormal flow velocity waveforms across the pulmonary valve (PV), was diagnosed in 12.9% (16/124) of recipients at TTTS diagnosis. Postnatal RVOTO was found in 6.7% (7/105) of surviving recipients. All recipients with severe postnatal RVOTO showed prenatal RVOTO at TTTS diagnosis. In 5.6% (6/108) of cases, prenatal RVOTO appeared only after laser therapy, and in 1.9% (2/108), this progressed to mild postnatal pulmonary stenosis. Elevated peak systolic PV velocities were more frequently associated with postnatal RVOTO compared with prenatal finding of functional pulmonary atresia. Postnatal RVOTO was associated with early manifestation of TTTS but was equally found in all Quintero stages.

CONCLUSION

In the spectrum of postnatal RVOTO, severe cases show prenatal RVOTO at TTTS diagnosis. However, RVOTO can develop after laser or even in the neonatal period and in all Quintero stages. A potential risk factor for postnatal RVOTO is early TTTS manifestation.

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.