Twin reverse arterial perfusion: Timing of intervention

Individualized intervention and growth dynamics assessment in TRAP sequence with conjoined twins based on radiofrequency ablation

BACKGROUND

Twin reversed arterial perfusion (TRAP) sequence with conjoined twins (CTs) represents an exceedingly rare and critical complication in monochorionic monoamniotic (MCMA) twin pregnancies. High mortality rates are associated with this condition, making early diagnosis and management crucial for improving survival outcomes, particularly for the pump twin.

CASE PRESENTATION

This case report focuses on a unique instance of TRAP-associated CTs, diagnosed at 13 weeks and 1 day of gestation. Management involved detailed ultrasonography and radiofrequency ablation (RFA) at 18 weeks and 5 days to interrupt the blood supply to the non-viable acardiac twin. This intervention allowed the pump twin to continue normal development, culminating in a cesarean delivery at 35 weeks and 1 day. The newborn showed a healthy postnatal outcome with no significant neurodevelopmental deficits noted at follow-up.

CONCLUSIONS

Early identification and tailored intervention are essential in cases of TRAP sequence associated with conjoined twins. This case exemplifies the potential of integrated multidisciplinary approaches and timely use of RFA, which significantly enhance the prognosis for the viable twin. These strategies are vital for managing complex MCMA pregnancies and can inform future clinical practices.

Outcomes of Intrauterine Interventions in Twin Reversed Arterial Perfusion (TRAP) Sequence: A Systematic Review of the Literature Over the Past 35 Years

Twin reversed arterial perfusion (TRAP) sequence is an uncommon disease affecting monochorionic twin pregnancies. The diagnosis can be made by ultrasound allowing to plan optimal antenatal management. An electronic search was conducted from inception to July 2024 to systematically evaluate and compare the outcomes of different intrauterine interventions in this condition. Eighty-two studies were included, and 859 women with a prenatal ultrasound diagnosis of TRAP sequence with a total of 1763 fetuses were studied. The mean maternal age was 24.2 years (range 19-40) and the mean gestational age at diagnosis was 19.6 weeks (range 10-32). A total of 792 pregnancies were reported in which a fetal intervention was performed over the past 35 years. The mean gestational age at fetal intervention was 22.1 weeks (range 11-32). The two most frequent fetal interventions were radiofrequency ablation, performed in 293 cases and laser umbilical cord coagulation in 140 cases. Overall, 684 out of 828 non-acardiac fetuses following fetal intervention survived (82.6%) compared with 49 out of 76 (64.5%) non-acardiac fetuses in pregnancies managed expectantly (p = 0.0001). A higher survival rate was seen in fetuses undergoing umbilical cord ligation (100%) although this procedure was performed in only 8 women. Survival rates were 88.9%, 79.9%, 78.9% and 77.9% for monopolar coagulation of the umbilical cord, laser coagulation of the umbilical cord, fetoscopic laser ablation of placental anastomoses and radiofrequency ablation, respectively. Our results show that the survival rate is higher in patients with TRAP who have a prenatal intervention compared with those who have prenatal expectant management. The survival rate varies depending on the modality used for the prenatal intervention. Future studies are necessary to investigate the impact of the gestational age at the time of the procedure on the survival rate depending on the prenatal therapeutic modality.

[TRAP (Twin Reversed Arterial Perfusion) Sequence in the Third Trimester]

The twin reversed arterial perfusion (TRAP) sequence is a complex and rare malformation syndrome that can occur in monochorionic twin pregnancies. It is characterized by vascular anastomoses and partial or total malformation of the heart and extremities of one of the fetuses. This leads to a hemodynamic dependence of the "parasitic" fetus (acceptor) from the "pump fetus" (donor). The therapeutic goal is to maximize the survival chances of the pump fetus. Although the optimal time for the therapeutic intervention, using radiofrequency ablation or ultrasound laser coagulation, is not clear yet, it is internationally recommended to be performed before gestational week 16. We present the case of an undiagnosed und therefore unusual monochorionic monoamniotic pregnancy in gestational week 34, in our perinatal center and demonstrate the impressive maximal expression of an untreated TRAP sequence.

Twin Reversed Arterial Perfusion Sequence Diagnosed Late in the Third Trimester: A Case Report and Literature Review

The twin reversed arterial perfusion (TRAP) sequence is a rare complication associated with monochorionic twins. It is characterized by blood flow from the umbilical artery of the normal (pump) twin to the umbilical artery of the abnormal (acardiac) twin via artery-to-artery anastomosis. This condition is associated with 100% mortality in the acardiac twin and a high rate of perinatal morbidity and mortality in the pump twin, primarily due to intrauterine hypoxic injury, heart failure, and prematurity. Following delivery, the surviving pump twin may experience adverse neurodevelopmental outcomes and heart failure, necessitating ongoing follow-up care. The goal of managing pregnancies complicated by the TRAP sequence is to deliver a healthy, near-term pump twin through early detection, timely intervention, and continuous follow-up. However, in low-resource settings, such as the case presented here, the condition may progress undiagnosed into the third trimester due to a lack of experienced physicians and/or obstetric ultrasound scans. This case report serves as an entry point for a comprehensive review of the literature on management options for the TRAP sequence, specifically focusing on factors to consider when managing patients conservatively in resource-limited environments or in cases that are referred or diagnosed late.

Cord Occlusion in Twin Reversed Arterial Perfusion Sequence: A Retrospective Study of Laser Photocoagulation versus Radiofrequency Ablation

INTRODUCTION

Twin reversed arterial perfusion (TRAP) sequence is a rare condition complicating monozygotic multiple gestations. Prenatal management via umbilical cord occlusion (UCO) of the anomalous twin has been shown to improve pump twin survival. We compared outcomes of gestations with high-risk TRAP sequence treated with mid-trimester UCO using laser photocoagulation versus radiofrequency ablation (RFA).

METHODS

This is a retrospective, single-center, cohort study of all patients with high-risk TRAP sequence who underwent UCO from 2006-2023. High-risk criteria were defined as follows: larger abdominal circumference of the anomalous twin, polyhydramnios, critically abnormal Doppler waveforms in the pump twin, hydrops in the pump twin, and/or monoamniotic twins. The primary outcome was 30-day survival of the pump twin.

RESULTS

The 74 patients were divided equally between the laser and RFA groups. For the 2 groups, mean gestational age (GA) at UCO (20.5 ± 2.3 vs. 20.7 ± 3.1 weeks, p = 0.987) and mean GA at delivery (35.2 ± 4.6 vs. 34.5 ± 5.7 weeks, p = 0.812) were similar. The 30-day neonatal survival rate did not differ (91.9% [34/37] vs. 89.2% [33/37], OR: 1.37 [0.29-6.61], p = 0.692).

CONCLUSION

No difference in 30-day neonatal survival was identified in patients with high-risk TRAP sequence who underwent mid-trimester UCO by laser versus RFA.

Monochorionic Twin Complications and Fetoscopic Interventions

Monochorionic twins are at risk for complications due to the presence of placental vascular anastomoses, including twin-twin transfusion syndrome, twin anemia-polycythemia sequence, selective fetal growth restriction, and twin reversed arterial perfusion sequence. While ultrasound is the primary modality to screen for the development of these complications, MRI plays an important role in assessing monochorionic twin pregnancies for the development of other complications, such as neurologic injury. In this article, the authors review the ultrasound imaging findings associated with monochorionic twin complications, management options, and the role for MRI in these pregnancies.

Fetal magnetic resonance imaging, ultrasound, and echocardiography findings in twin reversed arterial perfusion sequence

BACKGROUND

Twin reversed arterial perfusion (TRAP) sequence is a rare complication of monochorionic multiple gestation pregnancies, in which the pump twin provides hemodynamic support to a nonviable co-twin (acardius). Fetal magnetic resonance imaging (MRI) is used to detect pump twin abnormalities, particularly brain ischemia, prior to fetal intervention to interrupt umbilical blood flow to the acardius.

OBJECTIVE

To summarize the imaging findings of TRAP sequence pregnancies in a large series.

MATERIALS AND METHODS

A single-center retrospective review was performed of all TRAP sequence pregnancies referred for fetal MRI (2004-2021). Fetal MRI, ultrasound, and echocardiography data were collected.

RESULTS

Eighty-eight TRAP sequence pregnancies with MRI were included (mean gestational age, 19.8±2.8 weeks). Demise of the pump twin was noted in two pregnancies at the time of MRI. By MRI, 12% (10/86) of live pump twins had abnormalities, including 3% (3/86) with brain abnormalities and 9% (8/86) with extra-cranial abnormalities. By echocardiography, 7% (6/86) of pump twins had structural cardiac abnormalities. Three acardius morphological subtypes were identified by MRI: acephalus (55%, 48/88), anceps (39%, 34/88), and amorphous (7%, 6/88). The mean ultrasound acardius to pump twin ratio A/P ratio, calculated for each twin pair as the ratio of the acardius trunk (and head, if present) plus limb volume to the pump twin estimated fetal weight) differed among the three acardius subtypes (P=.03). The mean A/P ratio moderately correlated with pump twin cardiothoracic ratio and combined cardiac output (Pearson's r=0.45 and 0.48, respectively, both P<.001).

CONCLUSION

Fetal MRI of TRAP sequence pregnancies found anomalies in a substantial number of pump twins. The three acardius subtypes differed in A/P ratio, which moderately correlated with the pump twin cardiothoracic ratio and combined cardiac output.

"The Strange Case of Dr Pump and Mr Acardiac": The Twin Reversed Arterial Perfusion (TRAP) Sequence in Two Monochorionic Monoamniotic (MCMA) Twin Pregnancies-Diagnosis, Prognosis and Management: Review of Literature

The Twin Reversed Arterial Perfusion (TRAP) Sequence is an extremely rare complication of monochorionic twin pregnancies, with one severely malformed twin (the "acardiac") lacking autonomous placental blood supply and being perfused by the co-twin (the "pump"), through arterio-arterial (and sometimes also veno-venous) vascular anastomoses located on the placental surface. The prognosis is poor: mortality is 100% in the acardiac twin because of its severe malformations and about 50-55% in the pump twin, mainly due to heart failure and prematurity. So, the goal of perinatal management of the TRAP twin pregnancy is to deliver a healthy and near-term pump twin without heart failure or fetal hydrops. Intuitively, the earlier the diagnosis, the better the outcome. Herein, we report two cases of monochorionic monoamniotic (MCMA) twin pregnancies complicated by the TRAP Sequence, which are of interest since the objective of early diagnosis was achieved by means of transvaginal and 3D ultrasound, two techniques which revealed themselves as being useful to this purpose but are underused in the literature. The second aim of this study is to provide an overview of literature data about the diagnosis, prognosis establishment, and management of this rare condition, which are still debated and unclear due to negligible poor-quality evidence.

The High-Risk Profile of Selective Growth Restriction in Monochorionic Twin Pregnancies

The present review aims to provide a critical appraisal of the sonographic diagnosis and follow-up and to evaluate the optimal clinical management of monochorionic twin pregnancies where one of the twins is complicated by selective fetal growth restriction (sFGR). The classification is based on the umbilical artery (UA) diastolic flow reflecting the outcome. If the sFGR twin has positive diastolic flow (Type I) then the prognosis is good, and it does not require close surveillance. Biweekly or weekly sonographic and Doppler surveillance and fetal monitoring are recommended strategies to detect unpredictable complications in type II and type III forms, which are defined by persistently absent/reverse end-diastolic flow (AREDF) or cyclically intermittent absent/reverse end-diastolic flow (iAREDF) in the umbilical waveforms, respectively. The latest forms are associated with an increased risk of unexpected fetal demise of the smaller twin and 10-20% risk of neurological injury in the larger twin in addition to the overall risk of prematurity. The clinical course can be affected by elective fetal therapy ('dichorinization' of the placenta with laser or selective fetal reduction) or elective delivery in the presence of severe fetal deterioration. The prediction of the clinical outcome in complicated cases of type II and III sFGR cases remains elusive. Novel routines in fetal and placental scans in order to predict neurological impairments and unexpected fetal death to optimize the delivery time-point are needed.