Twin-reversed arterial perfusion sequence associated with decreased fetal cerebral vascular impedance

"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.

Twin reversed arterial perfusion sequence-a rare and dangerous complication form of monochorionic twins: A case report

BACKGROUND

Twin reversed arterial perfusion (TRAP) sequence is an extremely rare congenital anomaly in monochorionic (MC) twins. The condition is characterized by a malformed fetus (acardiac twin) without cardiac activities being perfused by a structurally normal one (pump twin) via an artery-to-artery anastomosis in a reverse direction.

CASE SUMMARY

We described the first case of TRAP to receive laser surgery in Vietnam. The 26-wk pregnancy was originally misdiagnosed in another hospital as MC twins with single intrauterine fetal death. Following admission to our center, the diagnosis was amended to a 26-wk TRAP sequence stage IIb. The acardiac twin was 7.5 cm at the longest length, the ratio of the weight of the acardiac twin to the weight of the pump twin was more than 90%, the pump twin showed fetal distress with absent diastolic flow in umbilical artery of pump twin, and the peak systolic velocity in the middle cerebral artery = 1.6 MoM. We performed emergency laser photocoagulation of the acardiac twin’s umbilical cord. After surgery, we successfully maintained the pregnancy for 8 wk and ended it electively by cesarean section at 34 wk of gestation due to rupture of membranes.

CONCLUSION

TRAP should be appropriately diagnosed and treated early to avoid complications of the pump twin. Fetoscopic laser photocoagulation is a new and effective treatment for this condition.

Ultrasound assessment of twin reversed arterial perfusion sequence for the prediction of adverse pregnancy outcomes in the first trimester

OBJECTIVE

To investigate twin reversed arterial perfusion (TRAP) sequence for the prediction of TRAP-related adverse pregnancy outcomes at the gestational age of 11-14 weeks.

METHODS

Pregnant women in the first trimester diagnosed with TRAP were recruited at West China Second University Hospital from January 2015 to June 2018. Systematic screening for the pump twin's crown-rump length (CRL) and acardiac twin's upper pole-rump length (URL) was conducted using ultrasonic detection. The (CRL - URL)/CRL and URL/CRL ratios were used to assess the pregnancy outcomes for the pump twin. Twenty-one pregnant women aged 21-39 years with a gestation of 11-14 weeks were recruited.

RESULTS

TRAP was diagnosed on average (± standard deviation (SD)) at pregnancy week 13.1 ± 0.18. The pump twins' mean (± SD) CRL was 6.65 ± 1.1 cm. The incidence of intrauterine death for the pump twins was 19.0% (n = 4), the miscarriage rate was 14.3% (n = 3), and the live birth rate was 66.7% (n = 14). The (CRL - URL)/CRL ratios between the nonsurvival (intrauterine death and miscarriage) and survival groups significantly differed (0.33 ± 0.08 vs. 0.58 ± 0.08, p < 0.05). Similarly, the URL/CRL ratios between the nonsurvival and survival groups significantly differed (0.67 ± 0.08 vs. 0.42 ± 0.08, p < 0.05).

CONCLUSION

The (CRL - URL)/CRL and URL/CRL ratios were valuable indicators for determining pregnancy outcomes of pump twins with TRAP at an early gestational age.

Alterations in Fetal Doppler Parameters Before and Twenty-Four Hours After Radiofrequency Ablation for Twin Reversed Arterial Perfusion Sequence

Objective

To evaluate alterations in the fetal Doppler parameters of pump fetuses before and 24 h after radiofrequency ablation surgery for twin reversed arterial perfusion sequence (TRAPs).

Methods

This is a retrospective study of 28 pump fetuses in TRAPs and 28 normal control twins between 2016 and 2021. The fetal Doppler parameters, including the umbilical artery pulsatility index (UA-PI), middle cerebral artery peak systolic velocity (MCA-PSV), middle cerebral artery pulsatility index (MCA-PI), and cerebroplacental ratio (CPR), of the controls, and pump fetuses before and 24 h after surgery were compared.

Results

An increasing trend and a further increase in the MCA-PSV, MCA-PI, MCA-PSV Z score, and MCA-PI Z score after surgery were observed in pump fetuses with gestational age (GA) ≥20 weeks; however, such changes were not observed in those with a GA of <20 weeks. The UA-PI and CPR before and after surgery were not different between control and pump fetuses, whether the GA was ≥20 or <20 weeks.

Conclusion

In the middle second trimester, the pump fetus might suffer from high cardiac output rather than hypoxemia before surgery and congestive heart failure, or hemodilutional anemia after surgery. This may provide some theoretical evidence in favor of early intervention, rather than waiting for a more advanced GA, to avoid unnecessary hemodynamic alterations.

‘TRAP-ped with an Acardius’: Case Series of Twin Reversed Arterial Perfusion (TRAP) Sequence and Review of Literature

Twin reversed arterial perfusion (TRAP) sequence is a rare but severe condition that affects monochorionic (MC) multifetal pregnancies. In twin pregnancies, it is characterized by a normally developed twin and another twin with missing heart function (acardiac twin or TRAP twin). A variety of risks and complications may affect the normal twin. Management of such pregnancies can be either expectant or interventional. We report four cases of TRAP sequence treated in our institutions and supply an overview on currently existing literature. This case series demonstrates the heterogeneity in manifestations and clinical course of patients affected by this condition. Furthermore, it includes an acardius amorphous of considerable size delivered at 35.6 weeks of gestation.