Paradoxic activation of the renin-angiotensin system in twin-twin transfusion syndrome: an explanation for cardiovascular disturbances in the recipient

Intertwin discordance of aldosterone levels in amniotic fluid with placental anastomoses in monochorionic twins: Insight into the pathophysiology of twin-to-twin transfusion syndrome

INTRODUCTION

Our objective was to investigate the association between the presence of placental anastomoses and intertwin differences in renin-angiotensin-aldosterone activation in monochorionic twins using amniotic fluid aldosterone (AF-ALD) levels. In addition, this study also examined the association between AF-ALD and the ALD levels in the umbilical cord blood (UCB-ALD) in monochorionic twins.

MATERIAL AND METHODS

This prospective study included monochorionic diamniotic (MD) twin pregnancies that were not complicated by twin-to-twin transfusion syndrome (TTTS) at delivery. Amniotic fluid and umbilical cord vein blood samples were collected from each twin at delivery, and the ALD levels were measured subsequently. The MD twins were divided into two groups: those with placental anastomoses and those without anastomoses owing to fetoscopic laser surgery. The differences in the AF-ALD levels between the larger and smaller twins were analyzed.

RESULTS

The AF-ALD levels showed a strong and significant positive correlation with UCB-ALD levels in 131 MD twins (r = 0.804, p < 0.001). Intertwin differences were examined in 41 and 28 pairs of MD twins with and without placental anastomoses, respectively. The AF-ALD levels in the smaller twins were significantly higher than those in the larger twins among the pairs of MD twins with placental anastomoses (p = 0.003); however, no statistically significant intertwin differences were observed among the twins without placental anastomoses (p > 0.05).

CONCLUSIONS

The AF-ALD levels reflect the UCB-ALD levels in MD twins. The presence of placental anastomoses led to intertwin discordance in the ALD levels in MD twins even uncomplicated with TTTS. It was considered that monochorionic twins have this clinical background, and it leads to the development of TTTS.

Assessing the Impact of Hematological Changes in Pregnancy on Maternal and Fetal Death: A Narrative Review

Hematological changes during pregnancy encompass a wide range of alterations in blood composition and function, including variations in hemoglobin levels, red blood cell count, and coagulation factors. These changes can be physiological or pathological and may significantly impact maternal and fetal health outcomes. This narrative review examines the relationship between various hematological changes and disorders during pregnancy and their effects on maternal and fetal mortality and morbidity. We explore conditions such as anemia, sickle cell disease, thrombophilia, and blood-borne infections like malaria, as well as the impact of multiple pregnancies on hematological parameters. The review also discusses the effects of COVID-19 on maternal hematology. Key findings include the high prevalence of adverse perinatal outcomes associated with these conditions, including early miscarriages, preterm birth, low birth weight, intrauterine growth restriction, and increased risk of maternal complications. The importance of early screening, diagnosis, and appropriate management of hematological disorders during pregnancy is emphasized. This review highlights the need for a multidisciplinary approach to managing pregnant women with hematological changes to optimize maternal and fetal outcomes.

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.

Monochorionic Twins: TTTS, TAPS, and Selective Fetal Growth Restriction

With an increasing incidence of twin gestations, understanding the inherent risks associated with these pregnancies is essential in modern obstetrics. The unique differences in placentation in monochorionic twins leads to unique complications, including twin-to-twin transfusion syndrome, the twin anemia-polycythemia sequence, and selective fetal growth restriction. Not only does the understanding of the monochorionic placenta lead to an understanding of the pathophysiology of the complications of monochorionic twins, but it also has led to the development of highly effective directed fetal therapy via fetoscopic laser coagulation used in twin-to-twin transfusion syndrome.

Fetal metabolic adaptations to cardiovascular stress in twin-twin transfusion syndrome

Monochorionic-diamniotic twin pregnancies are susceptible to unique complications arising from a single placenta shared by two fetuses. Twin-twin transfusion syndrome (TTTS) is a constellation of disturbances caused by unequal blood flow within the shared placenta giving rise to a major hemodynamic imbalance between the twins. Here, we applied TTTS as a model to uncover fetal metabolic adaptations to cardiovascular stress. We compared untargeted metabolomic analyses of amniotic fluid samples from severe TTTS cases vs. singleton controls. Amniotic fluid metabolites demonstrated alterations in fatty acid, glucose, and steroid hormone metabolism in TTTS. Among TTTS cases, unsupervised principal component analysis revealed two distinct clusters of disease defined by levels of glucose metabolites, amino acids, urea, and redox status. Our results suggest that the human fetal heart can adapt to hemodynamic stress by modulating its glucose metabolism and identify potential differences in the ability of individual fetuses to respond to cardiovascular stress.

Molecular Mechanisms Underlying Twin-to-Twin Transfusion Syndrome

Twin-to-twin transfusion syndrome is a unique disease and a serious complication occurring in 10–15% of monochorionic multiple pregnancies with various placental complications, including hypoxia, anemia, increased oxidative stress, and ischemia-reperfusion injury. Fetoscopic laser photocoagulation, a minimally invasive surgical procedure, seals the placental vascular anastomoses between twins and dramatically improves the survival rates in twin-to-twin transfusion syndrome. However, fetal demise still occurs, suggesting the presence of causes other than placental vascular anastomoses. Placental insufficiency is considered as the main cause of fetal demise in such cases; however, little is known about its underlying molecular mechanisms. Indeed, the further association of the pathogenic mechanisms involved in twin-to-twin transfusion syndrome placenta with several molecules and pathways, such as vascular endothelial growth factor and the renin–angiotensin system, makes it difficult to understand the underlying pathological conditions. Currently, there are no effective strategies focusing on these mechanisms in clinical practice. Certain types of cell death due to oxidative stress might be occurring in the placenta, and elucidation of the molecular mechanism underlying this cell death can help manage and prevent it. This review reports on the molecular mechanisms underlying the development of twin-to-twin transfusion syndrome for effective management and prevention of fetal demise after fetoscopic laser photocoagulation.

Different expressions of cardiac biomarkers between different types of acquired right ventricular outflow tract abnormality in monochorionic twins

OBJECTIVE

To investigate the differences in amniotic fluid cardiac biomarkers and clinical features among types of right ventricular outflow tract (RVOT) abnormality in monochorionic (MC) twins.

METHOD

This prospective study included MC twins that underwent laser surgery. Recipient or larger twins (group A) and donor or smaller twins (group B) were assessed and divided into those with a normal right ventricular outflow tract (normal RVOT), functional pulmonary atresia (fPA), or pulmonary stenosis (PS). Amniotic fluid levels of NT-proBNP (afNT-proBNP) and cardiac troponin T (afTnT) were examined during surgery.

RESULTS

Of 190 fetuses in group A, there were 14 RVOT abnormality cases (including 7 fPA and 7 PS). No group B fetuses showed RVOT abnormality findings. In group A, later and earlier gestational age at surgery were observed in fPA (25.1±2.8 weeks) and PS groups (17.8±0.9 weeks). All survived PS cases demonstrated progressive pulmonary valve obstruction, not observed in fPA groups. AfNT-proBNP were significantly higher in fPA and PS than in normal RVOT group (p<0.05). AfTnT was significantly higher in group A with PS than fPA and normal RVOT groups (p<0.05).

CONCLUSION

Among RVOT abnormality types in group A, amniotic fluid cardiac biomarkers were differently expressed, and clinical features were also differentiated. These findings provide insight into the pathophysiological influence on RVOT in MC twins. This article is protected by copyright. All rights reserved.

Association of amniotic fluid natriuretic peptide levels with ductus venosus Doppler flow in recipient twins with twin-to-twin transfusion syndrome : DV flow and NT-proBNP in TTTS recipient twins

PURPOSE

This study examined the relationships between fetal quantitative Doppler parameters and amniotic fluid N-terminal prohormone brain natriuretic peptide (afNT-proBNP) levels as a biomarker of the increased cardiac load in recipient twins with twin-to-twin transfusion syndrome (TTTS).

METHODS

This single-center, prospective study included all monochorionic diamniotic (MD) twin pregnancies that were diagnosed with TTTS and underwent fetoscopic laser surgery. Doppler flow was used to measure the pulsatility index (PI) of the umbilical artery (UA), ductus venosus (DV), and middle cerebral artery (MCA) of each recipient and donor twins. The afNT-proBNP levels of recipient twins were examined at the time of surgery. The Spearman or Pearson correlation coefficients were used to assess the relationships between afNT-proBNP levels and Doppler parameters.

RESULTS

A total of 150 MD twin pregnancies were included. The afNT-proBNP levels of the recipient twins showed a stronger correlation with the DV-PI (r = 0.637; P < 0.001) of recipient twins than with the UA-PI and MCA-PI of recipient twins. The Doppler parameters of donor twins were scarcely correlated with the afNT-proBNP levels of the recipient twins.

CONCLUSION

A positive correlation between the DV-PI and afNT-proBNP levels of recipient twins with TTTS was observed. The recipient twin with an increased DV-PI is expected to be under a high cardiac load; therefore, DV-PI is a useful parameter for assessing increased NT-proBNP levels consecutively and noninvasively.

CLINICAL TRIAL REGISTRATION

This study was registered with Japanese Clinical Trial Registry "UMIN-CTR" ( http://www.umin.ac.jp/ctr/index-j.htm ; trial ID numbers UMIN000024486 and 000037702).

The heart after surviving twin-to-twin transfusion syndrome

BACKGROUND

The persistent changes in cardiac structure and function in children who survived twin-to-twin transfusion syndrome remain a matter of concern and controversy. Current fetal echocardiographic parameters and their postnatal evolution can help improve our understanding of the subject.

OBJECTIVE

To describe the echocardiographic changes of monochorionic fetuses affected by twin-to-twin transfusion syndrome, the recipient and the donor, before and after laser photocoagulation and to determine their evolution in the third trimester and during their first year of life.

STUDY DESIGN

An observational study was conducted including 55 uncomplicated monochorionic diamniotic twins and 78 pairs with twin-to-twin transfusion syndrome, 44 stage I-II and 34 stage III-IV, prospectively enrolled from 2015 until 2018. Comprehensive echocardiography was performed at 4 time periods: before laser photocoagulation, at 24 to 72 hours after surgery, at 28 to 30 weeks of gestation, and at 6 to 12 months after birth. Echocardiographic parameters were transformed to z-scores or indexed for heart area, estimated fetal weight, or body mass surface.

RESULTS

At diagnosis, recipients in all stages presented larger hearts (cardiothoracic ratio z-score: 2.77 [0.8] vs controls: -0.03 [0.5]; P<.001) and signs of ventricular hypertrophy (left end-diastolic ventricle wall thickness: 2.68 [0.7] vs controls -0.03 [0.7]; P<.001), along with systolic (cardiac index recipients: 317 [114] mL/min/kg vs controls: 400 [120] mL/min/kg, P<.001) and diastolic impairment (isovolumetric relaxation time z-score: 2.76 [0.6] vs controls: 0.05 [0.6]; P<.001). Donors presented smaller ventricular areas and diameters when compared with controls (left end-diastolic ventricle area z-score: -1.48 [1] vs 0.03 [0.9]; P<.001), along with decreased longitudinal motion (tricuspid annular plane systolic excursion z-score: -0.9 [1] vs controls -0.04 [1]; P<.001) and shorter ejection time z-score (-1.5 [0.7] vs controls: 0.0 [0.7]; P<.001). After surgery, an improvement in functional parameters was observed in both fetuses, whereas most morphometric changes prevailed in donors and recipients in the prenatal period. Postnatally, cardiac remodeling persisted in recipients (left relative wall thickness: 0.34 [0.02] vs controls: 0.30 [0.02]; P<.001), whereas donors mainly presented a decreased longitudinal motion in infancy (tricuspid annular plane systolic excursion z-score: -0.72 [0.7] vs controls: 0.23 [0.9]; P<.05).

CONCLUSION

Cardiac remodeling is present in both fetuses at the twin-to-twin transfusion syndrome diagnosis, whereas diastolic dysfunction is only significant in the recipient. Fetal therapy improves most echocardiographic parameters, although postnatally, the echocardiographic changes persist in both fetuses.

Monochorionic diamniotic twin pregnancies

About one in five twin pregnancies are monochorionic diamniotic. In these twins, transfusion imbalances may develop due to the invariably present vascular anastomoses. The most severe imbalance is twin-twin transfusion syndrome, which presents as a significant amniotic fluid difference diagnosed on ultrasound scan, usually before 26 weeks. Another transfusion imbalance is twin anemia polycythemia sequence, a severe hemoglobin difference occurring mainly after 26 weeks in previously uncomplicated pregnancies. Fetoscopic laser coagulation of the anastomoses addresses the cause of these transfusion imbalances. Besides transfusion imbalances, the monochorionic placenta may be unevenly divided, or one part may be dysfunctional, leading to an intertwin growth difference of more than 20%. Here, laser ablation of the anastomoses will usually not cure the problem but aims to protect the appropriately growing twin if the growth-restricted co-twin dies. In monochorionic twins, structural anomalies are twice as common as in singleton pregnancies, probably due to a teratogenic effect of the embryonic splitting or because of transfusion imbalances. In contrast, chromosomal anomalies appear less common, possibly because they more likely result in an early demise. Selective reduction is feasible in monochorionic pregnancies but carries increased risks of loss, miscarriage, and early birth than a selective reduction in a dichorionic setting. Finally, if one monochorionic twin dies spontaneously, its co-twin may acutely exsanguinate into the demised co-twin, which may result in the loss of both twins or brain damage in the surviving twin. This update addresses the pathophysiology, diagnosis, and management of these common complications in monochorionic diamniotic twin pregnancies.

Outcomes of fetoscopic laser surgery for twin-to-twin transfusion syndrome between 26 and 27 weeks of gestation in Japan

AIM

The purpose of this study was to investigate the outcomes of fetoscopic laser photocoagulation (FLP) for twin-to-twin transfusion syndrome (TTTS) in Japan.

METHODS

The retrospective cohort study (2012-2018) was conducted in monochorionic twin pregnancies that underwent FLP for TTTS between 26 and 27 weeks from 2012 to 2018. The perioperative data, maternal complications, gestational age (GA) at delivery, neonatal complications, and survival of infants at 28 days of age were analyzed. At term-equivalent age, severe neurological complications were identified by imaging study.

RESULTS

Of 644 patients, 28 (4.3%) underwent FLP between 26 and 27 weeks, and 26 were analyzed. FLP procedures were technically successful in all cases. There were no cases of major maternal complications after surgery. Preterm rupture of membranes occurred in 34.6% of cases, and the mean GA at delivery was 33.2 ± 3.1 weeks. The survival of both twins was found in 23 (88.4%) cases, and the perinatal survival rate of at least one twin at 28 days of age was 100%. Severe neurological complications were found in six (12.2%) cases out of 49.

CONCLUSIONS

FLP for TTTS between 26 and 27 weeks provided a good prognosis and caused no major maternal complications. However, severe neurological findings were found in 12% of infants.

Twin to twin transfusion syndrome

Twin to twin transfusion syndrome (TTTS) is a common complication that typically presents in the second trimester of pregnancy in 10-15% of monochorionic twins due to net transfer of volume and hormonal substances from one twin to the other across vascular anastomoses on the placenta. Without recognition and treatment, TTTS is the greatest contributor to fetal loss prior to viability in 90-100% of advanced cases. Ultrasound diagnosis of monochorionicity is most reliable in the first trimester and sets the monitoring strategy for this type of twins. The diagnosis of TTTS is made by ultrasound with the findings of polyhydramnios due to volume overload and polyuria in one twin and oligohydramnios due to oliguria of the co-twin. Assessment of bladder filling as well as arterial and venous Doppler patterns are required for staging disease severity. Assessment of fetal cardiac function also provides additional insight into the fetal cardiovascular impacts of the disease as well as help identify fetuses that may require postnatal follow up. Fetoscopic laser ablation of the communicating vascular anastomoses between the twins is the standard treatment for TTTS. It aims to cure the condition by interrupting the link between their circulations and making them independent of one another. Contemporary outcome data after laser surgery suggests survival for both fetuses can be anticipated in up to 65% of cases and survival of a single fetus in up to 88% of cases. However, preterm birth remains a significant contributor to postnatal morbidity and mortality. Long term outcomes of TTTS survivors indicate that up to 11% of children may show signs of neurologic impairment. Strategies to minimize preterm birth after treatment and standardized reporting by laser centers are important considerations to improve overall outcomes and understand the long-term impacts of TTTS.

The role of umbilical artery velocities in the clinical assessment of twin-twin transfusion syndrome at stage

OBJECTIVE

To analyze the discordances of the umbilical artery velocities between pregnancies with twin-twin transfusion syndrome (TTTS) at stage I and those with normal monochorionic-diamniotic (MCDA) twins, and investigate the value of their discordances in predicting TTTS at stage I.

METHODS

We recruited 58 twin pregnancies with TTTS at stage I and 60 normal MCDA twin pregnancies in a tertiary referral center retrospectively. The umbilical artery velocities and their discordances were compared between the normal and TTTS twins.

RESULTS

The discordances of umbilical artery mean diastolic velocity (UA-MDV), umbilical artery time-averaged maximum velocity (UA-TAmax), umbilical artery peak systolic velocity (UA-PSV), and umbilical artery end-diastolic velocity (UA-EDV) were higher in the TTTS group than in the normal group. In TTTS co-twins, the UA-MDV, UA-TAmax, UA-PSV, and UA-EDV in recipients were higher than those in donors. The discordances of UA-TAmax and UA-PSV were found to be independent predicting factors for TTTS at stage I.

CONCLUSION

Co-twin umbilical artery velocity discordances were significantly associated with stage I TTTS. The results suggest that UA-TAmax and UA-PSV might be new parameters for predicting TTTS at stage I.

Twin gestation and the burden of adult cardio-renal disease

The rate of twin births has increased by nearly 80% in recent decades largely due to advanced reproductive technologies. Twins are often born preterm and/or growth restricted which are independently associated with impaired renal and vascular development. Many preterm and twin infants are surviving into adulthood, albeit with an increased burden of chronic health conditions. Twinning as a research tool offers the unique opportunity to investigate the impact of genetics versus the environment on clinical outcomes. This educational review will focus on delineating our current understanding of the renal and cardiovascular development and long-term outcomes among twin born individuals. Specifically, existing literature regarding how twins differ in kidney size and function as well as vascular stiffness and hypertension profiles from singletons will be discussed. The unique situation of twin-twin transfusion syndrome which is associated with distinct short- and long-term cardio-renal disease will be highlighted. Ultimately, the ability to stratify risk of future cardio-renal disease at birth for infants born preterm and/or growth restricted, including twins, is important to guide clinical follow up. In addition, this early risk stratification could direct research efforts to better understand the mechanisms driving impaired organogenesis and allow for discovery of therapeutic interventions aimed at modifying disease progression and improving longevity in the most vulnerable infant subgroups.

Placental Anatomy and Function in Twin Gestations

With an increasing incidence of twin gestations, understanding the inherent risks associated with these pregnancies is essential in modern obstetrics. The unique differences in placentation in twins contribute to the increased risks. Monochorionic twins are susceptible to complications because of their unique placental architecture, including twin-to-twin transfusion syndrome, the twin anemia-polycythemia sequence, selective intrauterine growth restriction, and the twin reversed arterial perfusion sequence. Knowing the clinical correlations of placental anatomy in these gestations helps perinatal pathologists perform a more informed placental evaluation, allowing for better care for the mother and her children.

Prediction of Twin-to-Twin Transfusion Syndrome Using Characteristic Waveforms of Ductus Venosus in Recipient Twins

We aimed to investigate whether the alterations of time intervals and velocity-time integrals (VTIs) of ductus venosus (DV) Doppler flow could predict evolving twin-to-twin transfusion syndrome (TTTS) in monochorionic diamniotic (MD) twin pregnancies in the second trimester. DV Doppler waveforms of MD twin pregnancies were retrospectively analyzed. Time intervals and VTIs of the accelerating phase of S-wave (S1 and VTI-1), decelerating phase of S-wave (S2 and VTI-2) and phase of D-wave (D and VTI-diast) were measured in the recipient twins of TTTS and the larger twins of uncomplicated MD twins. Each parameter was normalized to total time intervals and VTIs. DV parameters of prerecipient twins in pre-TTTS conditions were analyzed. The pre-TTTS condition was defined as the condition within 2 weeks before when TTTS cases fulfilled the criteria. Both recipient twins in TTTS cases and prerecipient twins in pre-TTTS condition showed significantly shorter S1, longer S2, shorter D, smaller VTI-1, larger VTI-2 and smaller VTI-diast than did the larger twins in uncomplicated MD twins (p < .05). Receiver-operating characteristic curve analysis showed that VTI-2 had better performance, and VTI-2 >45.5% had 87.0% sensitivity, 90.9% specificity, 81.0% positive predictive value and 93.0% negative predictive value for detecting prerecipient twins. Recipient twins complicated with TTTS have characteristic alterations in time intervals and VTIs of DV Doppler flow, which is present even before fulfilling the TTTS criteria. Furthermore, VTI-2 >45.5% is a possible predictive parameter for TTTS in the second trimester.

Critical Coarctation of the Aorta in Selective Fetal Growth Restriction and the Role of Coronary Stent Implantation

INTRODUCTION

Monochorionic twins are at increased risk of congenital heart defects (CHDs). Up to 26% have a birth weight <1,500 g, a CHD requiring neonatal surgery, therefore, poses particular challenges.

OBJECTIVE

The aim of the study was to describe pregnancy characteristics, perinatal management, and outcome of monochorionic twins diagnosed with critical coarctation of the aorta (CoA).

METHODS

We included monochorionic twins diagnosed with critical CoA (2010-2019) at 2 tertiary referral centers, and we systematically reviewed the literature regarding CoA in monochorionic twins.

RESULTS

Seven neonates were included. All were the smaller twin of pregnancies complicated by selective fetal growth restriction. The median gestational age at birth was 32 weeks (28-34). Birth weight of affected twins ranged as 670-1,800 g. One neonate underwent coarctectomy at the age of 1 month (2,330 g). Six underwent stent implantation, performed between day 8 and 40, followed by definitive coarctectomy between 4 and 9 months in 4. All 7 developed normally, except for 1 child with neurodevelopmental delay. Three co-twins had pulmonary stenosis, of whom 1 required balloon valvuloplasty. The literature review revealed 10 cases of CoA, all in the smaller twin. Six cases detected in the first weeks after birth were treated with prostaglandins alone, by repeated transcatheter angioplasty or by surgical repair, with good outcome in 2 out of 6.

CONCLUSIONS

CoA specifically affects the smaller twin of growth discordant monochorionic twin pairs. Stent implantation is a feasible bridging therapy to surgery in these low birth weight neonates.

Cerebral oxygenation reflects fetal development in preterm monochorionic and dichorionic twins

BACKGROUND

Cerebral oxygenation (crSO₂) monitoring is increasingly used in high-risk infants. Monochorionic twins suffer from specific fetal pathologies that can affect cerebral hemodynamics. Limited data are available on crSO₂ and blood flow patterns in this population after birth.

OBJECTIVE

To evaluate crSO₂ changes in preterm monochorionic and dichorionic twins during the first 72 h of life.

METHODS

Near-infrared spectroscopy was used to measure crSO₂ in 62 infants from 31 twin pregnancies <32 weeks of gestation. The study group was divided into 4 subgroups: donor (1) and recipient (2) monochorionic twins (with twin-twin transfusion syndrome), fetal growth restriction (FGR) infants (3) and twins without fetal compromise (4).

RESULTS

There was significant difference in birth weight (p < 0.001) among 4 subgroups. We observed significant variation in crSO₂ among the subgroups using mixed model analysis (p < 0.001). The recipient twins exhibited the lowest crSO₂ (mean ± SE) throughout the study period (76 ± 0.3%), whereas the FGR and donor twins presented with the highest values (86 ± 0.3% and 83 ± 0.4% respectively). We found no statistically significant differences in neonatal mortality and morbidity among subgroups.

CONCLUSION

Our study revealed significant correlation between crSO₂ values postnatally and underlying fetal pathology in monochorionic and dichorionic preterm twins.

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.

Renal functional markers in extremely premature infants with and without twin-twin transfusion syndrome

OBJECTIVE

Describe renal function of preterm infants <29 weeks of gestational age (GA) with twin-twin transfusion syndrome (TTTS) who received laser therapy.

DESIGN

Retrospective analysis of premature TTTS compared with dichorionic-diamniotic (di-di) twins from 2006 to 2015. Primary outcome was biomarkers of renal injury.

RESULTS

Thirty-three TTTS-laser and 101 di-di newborns with similar GA at birth (26.4 ± 1.4 vs 26.9 ± 1.6 weeks, p = 0.07) were included. Creatinine and urea levels were higher in TTTS-laser group at day of life (DOL) 2-7 (123.5 ± 12.4 vs 75.8 ± 2 μmol/L, p = 0.0001 and 11.9 ± 1.1 mmol/L vs 8.7 ± 0.3 mmol/L, p = 0.0001) and DOL 8-14, (98.1 ± 14.2 vs 64.8 ± 2.3 μmol/L, p = 0.0001 and 9.1 ± 1.2 vs 5.4 ± 0.3 mmol/L, p = 0.0001). There was a significant effect of TTTS status on creatinine level at DOL 8-14.

CONCLUSION

In extremely preterm with TTTS treated by laser, biomarkers of renal function were higher compared with di-di twins in the first 2 weeks of life.

Fetal cardiovascular alterations in twin-to-twin transfusion syndrome

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.

Fetal cardiac findings and hemodynamic changes associated with severe lower urinary tract obstruction in utero

OBJECTIVES

To describe fetal echocardiographic findings associated with lower urinary tract obstruction (LUTO) and to compare anatomic and hemodynamic measurements between fetuses with LUTO and gestational age (GA)-matched controls, with an emphasis on quantitative indices of diastolic function and cardiac output.

METHODS

This was a retrospective cohort study of fetuses diagnosed with severe LUTO with giant bladder, which underwent at least one fetal echocardiogram at our center between January 2005 and June 2018. Fetuses with major congenital heart disease were excluded. Control fetuses did not have any structural or functional abnormalities and were GA-matched to the LUTO fetuses based on the time of the first fetal echocardiogram. Cardiac anatomy and hemodynamic measurements were compared between fetuses with LUTO and controls. In infants with LUTO, serial fetal and postnatal echocardiographic data were assessed, when available, and clinical outcomes were reviewed.

RESULTS

Twenty-six fetuses with LUTO and at least one fetal echocardiogram available were identified, one of which was excluded due to hypoplastic left heart syndrome, leaving 25 LUTO fetuses in the final cohort. The mean GA at the first fetal echocardiogram was 25.4 ± 5.1 weeks in the LUTO group and 25.3 ± 5.0 weeks in the control group. Common findings in fetuses with LUTO included cardiomegaly (40%), pericardial effusion (44%), right ventricular (RV) hypertrophy (64%) and left ventricular (LV) hypertrophy (48%). Compared with GA-matched controls, LUTO fetuses had lower ascending aorta Z-score (-0.10 ± 0.94 vs -0.93 ± 1.03; P = 0.02) and aortic isthmus Z-score (-0.14 ± 0.86 vs -1.62 ± 1.11; P < 0.001), shorter mitral valve inflow time indexed to cardiac cycle length (0.46 ± 0.04 vs 0.41 ± 0.06; P = 0.002), and worse (increased) LV myocardial performance index (0.39 ± 0.03 vs 0.44 ± 0.04; P < 0.001). In addition, the ratio of RV to LV cardiac index was higher in LUTO fetuses compared with controls (1.62 ± 0.13 vs 1.33 ± 0.11; P < 0.001). Of the 25 LUTO pregnancies, two were lost to follow-up, three underwent elective termination of pregnancy and three ended in intrauterine fetal demise. Four (16%) patients had mildly hypoplastic left-heart structures, comprising two with aortic arch hypoplasia and two with mitral and aortic stenosis.

CONCLUSION

In addition to presenting with cardiomegaly, pericardial effusion and ventricular hypertrophy, fetuses with LUTO demonstrate LV diastolic dysfunction and appear to redistribute cardiac output as compared to control fetuses, which may contribute to the development of left-heart hypoplasia. Copyright © 2019 ISUOG. Published by John Wiley & Sons Ltd.

Asymmetrical Hemodynamic Influence of Twin-Twin Transfusion Syndrome on Fetal E/e' by the Dual Gate Doppler Method in Recipient Twins

OBJECTIVES

To assess the hemodynamic influence of twin-twin transfusion syndrome (TTTS) on diastolic function, using left ventricle (LV) and right ventricle (RV) E/e' measured in the same cardiac cycle using the dual-gate Doppler (DD) method.

METHODS

This study included 56 monochorionic twin pregnancies that underwent fetoscopic laser surgery (FLS) for TTTS in 2015-2018. E/e' by the DD method was measured 24 h before and 4-7 days after FLS.

RESULTS

Recipients showed higher LV-E/e' Z score in stage I-, II-, and III-recipients (IIIr) and higher RV-E/e' Z score in stage III-donors and IIIr than donors (p < 0.05). After FLS, LV-E/e' Z score of recipients significantly decreased due to LV-E velocity Z score decrease (p < 0.05). RV-E/e' Z score after FLS significantly decreased due to RV-e' velocity Z score increase in recipients (p < 0.05).

CONCLUSIONS

E/e' by the DD method helped assess cardiac changes of recipients. LV-E/e' could assess early hemodynamic changes by TTTS, and RV-E/e' can assess later influence on cardiac diastolic function. Furthermore, in recipient twins, the decrease in LV-E/e' after FLS might reflect the improvement of volume overload and the decrease in RV-E/e' might reflect the improvement of diastolic relaxation function in the RV.

Cardiomegaly of the larger twin in monochorionic twin pregnancies warrants neonatal intensive care even without twin-to-twin transfusion syndrome

OBJECTIVES

Some monochorionic twin pregnancies need intensive cardiac management even in the absence of twin-to-twin transfusion syndrome after birth. The purpose of this study was to investigate risk factors related to persistent hypotension requiring cardiotonic agent use among monochorionic twin pregnancies without twin-to-twin transfusion syndrome.

STUDY DESIGN

This was a retrospective study of 316 monochorionic twin pregnancies without twin-to-twin transfusion syndrome (632 babies). All cases were treated in the neonatal intensive care unit. Hypotension was defined as mean arterial blood pressure below the norm for gestational age. Decreased left ventricular ejection fraction was defined as a value <60%. Dopamine, dobutamine and phosphodiesterase III inhibitor were used as cardiotonic agents for hypotension persisting even after adequate infusion.

RESULTS

Among the 632 cases, 33 (5.2%) needed cardiotonic agents for persistent hypotension. The frequency of persistent hypotension with decreased left ventricular ejection fraction was significantly higher among larger twins (4.4%) than among smaller twins (0.6%, p = 0.0038). In larger twins, multivariate analysis showed that Z-score for cardiothoracic area ratio (odds ratio, 2.31; p < 0.001), tricuspid regurgitation (odds ratio, 6.34; p = 0.015) and gestational age at delivery (odds ratio, 0.66; p < 0.001) correlated with persistent hypotension. In smaller twins, univariate analysis showed gestational age at delivery, birth weight, Z-score for birth weight and Z-score for cardiothoracic area ratio of the larger twin were related to persistent hypotension. Concentration of brain natriuretic peptide in the umbilical vein in larger and smaller twins were significantly correlated (coefficient of correlation = 0.792, p < 0.001).

CONCLUSIONS

In monochorionic twin pregnancies, attention needs to be given to cardiac size along with amniotic fluid and fetal growth. Both larger and smaller twins carry risks of persistent hypotension after birth. Close observation is needed, especially in cases where the larger twin displays cardiomegaly despite absence of twin-to-twin transfusion syndrome.

Bisphosphonate therapy in an infant with generalized arterial calcification with an ABCC6 mutation

Generalized arterial calcification of infancy (GACI) is a rare genetic disorder with high infantile mortality, described to be due to ENPP1, and less commonly ABCC6 mutations. Bisphosphonate treatment has been described to improve survival in ENPP1-positive GACI patients, but few studies have described bisphosphonate treatment in ABCC6-positive patients. Without therapy, patients will die before 6 months of age. Our patient is now 3 years old, former recipient twin of twin-to-twin transfusion syndrome (TTTS). Initial fetal echocardiogram at 19 weeks showed calcifications of the ascending aorta and pulmonary artery (PA). She underwent utero laser therapy, and despite resolution of the TTTS, her follow-up scans showed progressive calcification of the aorta and PA. Postnatal echocardiogram showed calcification and supravalvar stenosis of the aorta and PA. CT on day of life 6 showed calcifications in the PAs, aortic arch, and descending aorta. Quantification of valvular calcification can be difficult; in our patient, increasing outflow tract gradient on echocardiogram was used to monitor disease progression. Molecular testing revealed an ABCC6 gene mutation. She was started on weekly IV pamidronate (0.1-0.3 mg/kg/week) on day 8 of life then transitioned to oral etidronate (15-20 mg/kg/day). Given progressive supravalvar aortic and pulmonary stenosis, she underwent surgical repair with patch augmentation of the PA and ascending aorta at 4 months old. She has done well post-operatively, continuing on enteral bisphosphonate therapy with no side effects to date. Her identical twin was confirmed to have the same mutation and remains asymptomatic with no calcifications. Aggressive bisphosphonate therapy should be started as soon as possible in patients with infantile arterial calcinosis due to ABCC6 or ENPP1 mutations. Echocardiographic evaluation can be used to monitor disease progression by arterial gradients. Molecular testing is also essential to evaluate for possible co-morbidities in these patients and pregnancy management for the future.

Cardiac pathophysiology in twin-twin transfusion syndrome: new insights into its evolution

OBJECTIVES

In twin-twin transfusion syndrome (TTTS), unbalanced transfer of vasoactive mediators and fluid from the donor to the recipient cotwin alters their cardiovascular function. The aims of this study were to describe the impact of TTTS on fetal cardiac function in a large cohort of monochorionic-diamniotic (MCDA) pregnancies, and determine the early hemodynamic response to selective fetoscopic laser photocoagulation (SFLP).

METHODS

Echocardiography was performed in 145 MCDA pregnancies, including 26 uncomplicated MCDA, 61 TTTS Stages I+II and 58 TTTS Stages III+IV pregnancies, prior to SFLP for TTTS. Echocardiographic data after SFLP were available in a subset of 41/119 (34%) TTTS cases at a mean of 1.7 ± 1.9 days. Mitral (MAPSE) and tricuspid (TAPSE) annular systolic excursion, myocardial performance index (MPI), tissue Doppler velocities (E', A', S') and filling pressures (E/E') were measured and transformed into Z-scores. Ventricular pressure was estimated from peak atrioventricular regurgitation velocity.

RESULTS

Left ventricular hemodynamics of the recipient twin were affected in early TTTS. In all stages of TTTS, left MPI and E/E' of the recipient twin were elevated in comparison to those of the donor (all P < 0.05), with reduced recipient left S' in TTTS Stages III+IV (P < 0.001). Ventricular pressure was elevated for gestational age (median, 42 mmHg (range, 20-65 mmHg)) in 11 of 14 recipients in which this parameter was measured. Between-group difference in right ventricular E/E' was significant only in TTTS Stages III+IV recipients compared with TTTS Stages I+II (P = 0.007) and uncomplicated MCDA (P = 0.041). Recipient left and right MPI decreased while S', MAPSE and TAPSE increased after SFLP; in donors, left E/E' and cardiac output increased.

CONCLUSIONS

Cardiac function of the recipient twin in TTTS is abnormal, even in the early stages of the disease. Left ventricular filling pressures are elevated and systolic function is decreased before abnormalities in the right heart become apparent. SFLP produces rapid hemodynamic improvement. Copyright © 2017 ISUOG. Published by John Wiley & Sons Ltd.

Twin-twin transfusion syndrome - What we have learned from clinical trials

Monochorionic twin pregnancies are at increased risk for adverse outcome compared to dichorionic twin pregnancies and singletons. Monochorionic-specific complications include twin-twin transfusion syndrome (TTTS), twin anemia-polycythemia sequence, single intrauterine fetal demise and its consequences on the co-twin, and selective intrauterine growth restriction. Whereas the natural history of monochorionic-specific complications carries a high risk of fetal death or severe neurologic disability, a framework now exists, based on well-designed clinical trials, for optimal treatment of these entities. Fetoscopic selective laser coagulation of anastomotic vessels on the chorionic plate has been clearly demonstrated to improve survival and neurologic outcomes for Quintero stage ≥2 TTTS. However, many challenges remain unsolved, the most important of which is preterm premature rupture of membranes. Further improvement in the outcomes of monochorionic pregnancies will require improvements in the rate of premature delivery, and improved diagnosis and treatment strategies for early and late onset TTTS.

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.

Estimated combined cardiac output and laser therapy for twin-twin transfusion syndrome

INTRODUCTION

Twin-twin transfusion syndrome (TTTS) is the major cause for fetal demise in monochorionic diamniotic pregnancies. Estimated combined cardiac output (CCO) has not been studied in this setting. The primary aims of this study were to compare CCO in twin donor and recipient fetuses and assess differences in CCO before and after laser coagulation therapy. A secondary aim was to evaluate the relationship of CCO with perinatal mortality, defined as intrauterine or neonatal mortality (≤30 days of age) in fetuses that underwent laser coagulation therapy.

METHODS

We performed a retrospective review of fetuses with TTTS who received echocardiograms prior to laser therapy. Prelaser echocardiograms were performed in 66 fetuses, of which 45 (21 donor and 24 recipient) survived to the postlaser echocardiogram.

RESULTS

Donor CCO increased from a mean of 487±137 mL/min/kg prelaser to 592±128 mL/min/kg postlaser (P=.025). There was no significant change in mean recipient CCO from prelaser 551±165 mL/min/kg to postlaser 575±112 mL/min/kg (P=.564). In recipient fetuses, higher prelaser CCO correlated with increasing Quintero stage (P=.010) and perinatal mortality (P=.003). Thirty-day postnatal outcome data were available for 38 fetuses, of whom 34 (89%) survived. Amongst survivors, 25 (74%) experienced an increase in CCO, while 9 (26%) experienced a decrease in CCO (P=.010). Donor fetuses had higher CCO after laser therapy.

CONCLUSIONS

Higher prelaser CCO in recipient fetuses may indicate more advanced disease. Fetuses who exhibit a decrease in CCO after therapy laser may be at higher risk for perinatal mortality.

Atypical twin-to-twin transfusion syndrome: prevalence in a population undergoing fetoscopic laser ablation of communicating placental vessels

BACKGROUND

The diagnosis of twin-to-twin transfusion syndrome (TTTS) usually relies the presence of polyhydramnios in one sac with concomitant oligohydramnios in the other sac in a monochorionic diamniotic twin pregnancy. However, TTTS does not always show a linear progression and may present with cardiac compromise or critically abnormal Doppler velocimetry in either fetus before fluid measurements meet the typically used cutoff.

OBJECTIVE

The aim of this study was to investigate the prevalence of atypical presentations of TTTS in a population undergoing laser fetoscopy.

STUDY DESIGN

We performed a retrospective review of our database of TTTS laser fetoscopy from 2003 to the present. Our center is the regional referral center in the Pacific Northwest for minimally invasive treatment of complicated monochorionic twin pregnancies. Cases were labeled as "atypical" if fluid discordance did not meet formal TTTS criteria (oligohydramnios defined as maximum vertical pocket [MVP] <2 and polyhydramnios defined as MVP >8 before 20 weeks and >10 after 20 weeks). The rationale for consideration of laser fetoscopy was other evidence of severe TTTS such as significant cardiac compromise, evidence of twin anemia polycythemia sequence (TAPS), or persistent critically abnormal cord Dopplers.

RESULTS

Three hundred seventy-nine cases of fetoscopic laser ablation for TTTS and its variants were available for review. Sixteen cases were excluded for a triplet pregnancy, 4 due to septostomy prior to referral to our center, 3 for monoamniotic pregnancy, and 11 for previous laser fetoscopy. Three hundred forty-five cases remained for evaluation. Among these, 25 cases were identified as "atypical," equaling 7.24% of our population. Eleven of these were for stage 3 recipient disease, 3 were for stage 4 recipient disease, 4 were for stage 3 both in recipient and donor, 4 were for stage 3 donor disease, and 3 were for spontaneous TAPS.

CONCLUSION

In TTTS, severity of fetal compromise does not consistently correlate with fluid abnormalities meeting established criteria. This may be especially true in rapidly progressing cases. Attempts at rigid diagnostic amniotic fluid criteria may underestimate the severity and incidence of TTTS. This underscores the importance of careful surveillance, including arterial and venous Doppler velocimetry, of all monochorionic pregnancies.

Twin-to-Twin Transfusion Syndrome: Definition, Staging, and Ultrasound Assessment

Objective: The purpose of this article is to review the definition of twin-to-twin transfusion syndrome (TTTS) and the sonographic diagnostic assessment of these cases prior to therapy.

Materials and Methods: The article addresses the terminology used to refer to the condition and describes the systematic ultrasound assessment of the condition, including the ultrasound diagnosis, the staging of the disease, cervical assessment and pre-operative mapping.

Results: From an etymologic and medical point of view, the term ‘fetofetal transfusion’ is more appropriate than ‘TTTS’. However, as the latter, and its attendant acronym TTTS, have been widely adopted in the English language, it is impractical to change at this point. TTTS is defined sonographically in the combined presence of a maximum vertical pocket (MVP) of 8 cm or greater in one sac and 2 cm or less in the other sac, regardless of the gestational age at diagnosis. Staging of the condition using the Quintero staging system is practical, reproducible, and accepted. Transvaginal cervical length assessment should be an integral part of the ultrasound evaluation. Pre-operative mapping to anticipate the location of the placental vascular anastomoses and avoid injuring the dividing membrane is also discussed.

Conclusions: The term ‘TTTS’ can continue to be used in the English medical literature. The condition can be diagnosed and assessed following a systematic ultrasound methodology. The use of such ultrasound methodology breaks the examination into a distinct set of components, assuring a comprehensive examination and proper communication among caregivers.

The Placenta in Twin-to-Twin Transfusion Syndrome and Twin Anemia Polycythemia Sequence

Twin-to-twin transfusion syndrome (TTTS) and twin anemia polycythemia sequence (TAPS) are complications unique to monochorionic twin pregnancies and their shared circulation. Both are the result of the transfusion imbalance in the intertwin circulation. TTTS is characterized by an amniotic fluid discordance, whereas in TAPS, there is a severe discordance in hemoglobin levels. The article gives an overview of the typical features of TTTS and TAPS placentas.

Cardiac Manifestations of Twin–to–Twin Transfusion Syndrome

This review addresses the physiology of monochorionic diamniotic (MC/DA) twins and the potential for twin–twin transfusion syndrome (TTTS). It focuses on the underlying cardiovascular pathophysiology of TTTS and the cardiovascular impact of TTTS for both the recipient and the donor twin. It explains the principles for assessment and monitoring of these cardiovascular changes and how these may be used to guide pregnancy management. Finally, it describes the effect of treatment on the altered hemodynamics and how this can influence pregnancy and perinatal management, as well as longer-term follow-up.

Fetal cardiovascular hemodynamics in twin-twin transfusion syndrome

Twin-twin transfusion syndrome (TTTS) complicates 10-15% of monochorionic-diamniotic (MCDA) pregnancies. It originates from unbalanced transfer of fluid and vasoactive mediators from one twin to its co-twin via placental anastomoses. This results in hypovolemia in the donor and hypervolemia and vasoconstriction in the recipient twin. Consequently, the recipient demonstrates cardiovascular alterations including atrioventricular valve regurgitation, diastolic dysfunction, and pulmonary stenosis/atresia that do not necessarily correlate with Quintero-stages. Selective fetoscopic laser photocoagulation of placental vascular anastomoses disrupts the underlying pathophysiology and usually improves cardiovascular function in the recipient with normalization of systolic and diastolic function within weeks after treatment. Postnatal studies have demonstrated early decreased arterial distensibility in ex-donor twins, but 10-year follow up is encouraging with survivors showing normal cardiovascular function after TTTS. However, prediction and appropriate early management of TTTS remain poor. Assessment of the cardiovascular system provides additional insight into the pathophysiology and severity of TTTS and may permit more targeted early surveillance of MCDA pregnancies in future. It should form an integral part of the diagnostic algorithm.

Childhood cardiac outcome after intrauterine laser treatment of twin-twin transfusion syndrome is favourable

AIM

Intrauterine laser treatment is used to alleviate abnormal circulatory load and cardiac morbidity affecting foetuses with twin-twin transfusion syndrome (TTTS). We conducted this childhood follow-up study to fill the gap in knowledge about final cardiac outcomes after such interventions.

METHODS

We investigated 19 TTTS pairs - 11 male and eight female - with a mean age of four and a half years (range 1.1-9.9) using 2D, blood flow and tissue Doppler, 3D and speckle tracking echocardiography, and compared them with 19 age-matched and gender-matched singletons.

RESULTS

The only observed differences in cardiac structure or function between the donors and recipients were related to diastolic ventricular filling. Recipients had a lower left ventricular ratio of early and late diastolic filling compared with their donor cotwins [1.48(0.35) versus 1.66 (0.28), p < 0.05], but not compared with singleton controls. All observations, except one, were within the reference limits. Speckle tracking could not demonstrate any group differences in systolic ventricular function, besides marginally lower ventricular strain in the donors than controls.

CONCLUSION

Double survivors of laser-treated TTTS showed only minor within-pair differences in diastolic cardiac function at childhood follow-up. Cardiac function in TTTS twins compared well to singleton controls, suggesting a favourable long-term outcome.

Pathophysiological mechanisms of high-intensity focused ultrasound-mediated vascular occlusion and relevance to non-invasive fetal surgery

High-intensity focused ultrasound (HIFU) is a non-invasive technology, which can be used occlude blood vessels in the body. Both the theory underlying and practical process of blood vessel occlusion are still under development and relatively sparse in vivo experimental and therapeutic data exist. HIFU would however provide an alternative to surgery, particularly in circumstances where serious complications inherent to surgery outweigh the potential benefits. Accordingly, the HIFU technique would be of particular utility for fetal and placental interventions, where open or endoscopic surgery is fraught with difficulty and likelihood of complications including premature delivery. This assumes that HIFU could be shown to safely and effectively occlude blood vessels in utero. To understand these mechanisms more fully, we present a review of relevant cross-specialty literature on the topic of vascular HIFU and suggest an integrative mechanism taking into account clinical, physical and engineering considerations through which HIFU may produce vascular occlusion. This model may aid in the design of HIFU protocols to further develop this area, and might be adapted to provide a non-invasive therapy for conditions in fetal medicine where vascular occlusion is beneficial.

Cardiac function in 10-year-old twins following different fetal therapies for twin-twin transfusion syndrome

OBJECTIVES

To compare cardiac function at 10 years of age in four groups of monochorionic diamniotic (MCDA) twin pairs: uncomplicated MCDA twins (n = 6) (Group 1); twins that had had twin-twin transfusion syndrome (TTTS) managed by amnioreduction (TTTS-amnio, n = 9) (Group 2) or laser photocoagulation (TTTS-laser, n = 10) (Group 3); and dichorionic diamniotic controls (DCDA, n = 6) (Group 4).

METHODS

Echocardiograms optimizing apical four-chamber and short-axis left ventricular views were stored for offline speckle-tracking analysis, blinded to twin type. Myocardial long-axis shortening and lengthening velocities were measured using pulsed Doppler ultrasound at the cardiac base. M-mode measurements of fractional shortening (short axis) and maximal excursion of the atrioventricular annulus (four-chamber) were recorded. Syngo Vector Velocity Imaging software tracked left ventricular myocardial motion offline to produce free wall strain, strain rate and rotation. Intertwin pair and group differences were investigated using ANOVA.

RESULTS

Cardiac measurements were within the normal ranges for 10-year-olds. No significant within-twin-pair and intergroup differences were found in current size, heart rates, strain or strain rate. Compared to DCDA controls, TTTS twins showed less cardiac rotation (TTTS-laser, P < 0.001 and TTTS-amnio, P = 0.054) with significant intertwin reduction in the ex-recipient (TTTS-amnio, P = 0.006) and larger MCDA twins (P = 0.027) compared with their cotwins. A similar pattern was seen in left ventricular early diastolic mitral valve tissue velocity (MVE') in all monochorionic groups, but only achieving significance in TTTS-amnio twins (P = 0.037). Intrapair differences in rotation and MVE' were significantly different following treatment at Quintero stages III or IV.

CONCLUSIONS

Within-twin-pair patterns of left ventricular rotation and diastolic function differ at 10 years of age in ex-recipients of TTTS twins treated with amnioreduction compared with those treated by laser photocoagulation and controls. .

Diagnosis and treatment of fetal cardiac disease: a scientific statement from the American Heart Association

BACKGROUND

The goal of this statement is to review available literature and to put forth a scientific statement on the current practice of fetal cardiac medicine, including the diagnosis and management of fetal cardiovascular disease.

METHODS AND RESULTS

A writing group appointed by the American Heart Association reviewed the available literature pertaining to topics relevant to fetal cardiac medicine, including the diagnosis of congenital heart disease and arrhythmias, assessment of cardiac function and the cardiovascular system, and available treatment options. The American College of Cardiology/American Heart Association classification of recommendations and level of evidence for practice guidelines were applied to the current practice of fetal cardiac medicine. Recommendations relating to the specifics of fetal diagnosis, including the timing of referral for study, indications for referral, and experience suggested for performance and interpretation of studies, are presented. The components of a fetal echocardiogram are described in detail, including descriptions of the assessment of cardiac anatomy, cardiac function, and rhythm. Complementary modalities for fetal cardiac assessment are reviewed, including the use of advanced ultrasound techniques, fetal magnetic resonance imaging, and fetal magnetocardiography and electrocardiography for rhythm assessment. Models for parental counseling and a discussion of parental stress and depression assessments are reviewed. Available fetal therapies, including medical management for arrhythmias or heart failure and closed or open intervention for diseases affecting the cardiovascular system such as twin-twin transfusion syndrome, lung masses, and vascular tumors, are highlighted. Catheter-based intervention strategies to prevent the progression of disease in utero are also discussed. Recommendations for delivery planning strategies for fetuses with congenital heart disease including models based on classification of disease severity and delivery room treatment will be highlighted. Outcome assessment is reviewed to show the benefit of prenatal diagnosis and management as they affect outcome for babies with congenital heart disease.

CONCLUSIONS

Fetal cardiac medicine has evolved considerably over the past 2 decades, predominantly in response to advances in imaging technology and innovations in therapies. The diagnosis of cardiac disease in the fetus is mostly made with ultrasound; however, new technologies, including 3- and 4-dimensional echocardiography, magnetic resonance imaging, and fetal electrocardiography and magnetocardiography, are available. Medical and interventional treatments for select diseases and strategies for delivery room care enable stabilization of high-risk fetuses and contribute to improved outcomes. This statement highlights what is currently known and recommended on the basis of evidence and experience in the rapidly advancing and highly specialized field of fetal cardiac care.

Renal tubular dysgenesis

Renal tubular dysgenesis (RTD) is a severe foetal disorder characterised by the absence or poor development of proximal tubules, early onset and persistent anuria (leading to oligohydramnios and the Potter sequence) and ossification defects of the skull. In most cases, early death occurs from pulmonary hypoplasia, anuria and refractory arterial hypotension. RTD may be acquired during foetal development or inherited as an autosomal recessive disease. Inherited RTD is genetically heterogeneous and linked to mutations in the genes encoding the major components of the renin-angiotensin system (RAS): angiotensinogen, renin, angiotensin-converting enzyme or angiotensin II receptor type 1. Mutations result in either the absence of production or lack of efficacy of angiotensin II. Secondary RTD has been observed in various situations, particularly in the donor twin of severe twin-to-twin transfusion syndrome, in foetuses affected with congenital haemochromatosis or in foetuses exposed to RAS blockers. All cases result in renal hypoperfusion. These examples illustrate the importance of a functional RAS in the maintenance of blood pressure and renal blood flow for humans during foetal life. The diagnosis of RTD in an anuric foetus with normal renal sonography results is important for the management of the foetus or neonate. Depending on the genetic or secondary cause of the disease, such findings can lead to genetic counselling or the prevention of recurrence in subsequent pregnancies.

What-and why-the pathologist should know about twin-to-twin transfusion syndrome

Approximately 20% of all twin pregnancies are monochorionic. Between 9% and 15% of all monochorionic twin gestations are complicated by severe chronic twin-to-twin transfusion syndrome (TTTS), characterized by a gradual shift of blood volume from the donor twin to the recipient twin through placental vascular connections [1 - 3] . The prognosis of severe, untreated chronic TTTS diagnosed in midtrimester fetuses is extremely poor, with mortality rates exceeding 70% [4] . Since publication of the results of the Eurofoetus trial in 2004, laser photocoagulation of the intertwin anastomoses has become accepted as the optimal first-line therapy for severe TTTS diagnosed before 26 weeks of gestation. While laser treatment of vascular communications was initially limited to selected fetal treatment centers, its increasingly widespread use has resulted in the exposure of more pathologists, even in less specialized institutions, to laser-treated placentas. Furthermore, the surge in laser coagulation has revived the general medical, scientific, and public interest in the placental and choriovascular findings in monochorionic twin placentas. The pathologist's understanding of the pathophysiology of TTTS and of TTTS-associated placental pathology, including the findings related to laser ablation of the anastomoses, can be of great benefit to the involved obstetric/neonatal/surgical team and, ultimately, to the patients. In this review, we summarize the current knowledge of the placental contributions to TTTS and other complications of monochorionic twinning and describe the strengths and limitations of placental examination in these settings. It is our expectation that overviews such as this may serve as a template to generate consensus guidelines for standardized and evidence-based pathologic evaluation of monochorionic twin placentas.