Twin reversed arterial perfusion (TRAP) sequence managed at 11+6 weeks with radiofrequency ablation

Introduction

Numerous methods explored for the management of twin reversed arterial perfusion (TRAP) sequence include introducing thrombogenic material (glucose, fibrin, gel, steel coil) or electrical energy to interrupt blood flow, fetoscopic ligation of the cord, and laser coagulation of the cord. A recent systematic review reported the superior outcome of intrafetal radiofrequency ablation (RFA) for the management of TRAP sequence [6]. The authors reported that most RFA procedures had been performed using 14–17 gauge (G) RFA needles focusing on an acardiac mass at an average age of 21 weeks of gestation (17–24 weeks). In this case report, we describe treatment of TRAP sequence using RFA with a 20 G needle focusing on a feeding artery on the placental surface at a gestational age of 11+6.

Case report

A 33-year-old female (gravida 1, para 0) presented at a gestational age of 5+5 (26 days after embryo transfer at a local clinic). She had suffered from Sjogren’s syndrome for 2 years. She tested positive for anti-Ro antibody, but had no definite organ involvement except eye dryness. On transvaginal ultrasound scanning, a single 8-mm gestational sac was detected along with a tiny yolk sac inside. At that time we thought it was a singleton pregnancy. On follow-up sonography 2 weeks later (gestational age of 7+5), a monochorionic diamniotic twin pregnancy was found with one twin heart beat recorded at 152 beats per minute and the other twin heart beat recorded at 70 beats per minute (Figure 1). The twins differed conspicuously in size (crown-to-rump lengths were 9.3 mm and 4.4 mm). We informed the mother that the smaller twin might not survive. On follow-up sonography 2 weeks later (gestational age of 9+5), a diagnosis of acardiac twin was made based on poor development of the upper extremities and cystic features above the thorax with relatively well-preserved lower extremities in the smaller twin (Figure 2). Reversed arterial perfusion to the acardiac twin through the umbilical cord was also detected. Synchronized heart beats of 188 beats per minute were evident in both twins. On serial sonographic examinations, the size of the acardiac twin gradually increased to 0.5 cm², 1.4 cm², and 4.2 cm² at gestational age of 7+5, 9+5, and 10+5, respectively. After counseling about the possible outcomes of the pregnancy and management options, the decision was made to perform RFA at gestational age of 11+6. Prior to starting the RFA procedure, transabdominal chorionic villi sampling was done. The vascular connection site of the arterio-arterial anastomosis, which showed arterial blood flow from the normal fetus to the acardiac member, was detected on the placental surface using the color power Doppler setting (Figure 3). A 20 G 150-mm RFA needle (Cosman Medical, Burlingame, CA, USA) was introduced to reach the anastomosis site through the placenta under the color power Doppler setting. No anesthetic was employed. RFA was performed at the vascular connection site on the placental surface (Figure 3) under color flow mapping guidance. RFA was performed in a cyclic manner, with 2 min of ablation and 1 min of rest. The duration of RFA was 5 min (two sets). Radiofrequency was generated with an RFG-1A Generator (Cosman Medical) with the temperature set to 90°C. Immediate cessation of blood flow in the target vessel after RFA procedure was detected. A normal fetal heart rate and normal movements were present in the normal fetus following RFA. On follow-up ultrasound after RFA, the size of the acardiac twin had decreased (4 cm² at gestational age of 12+5, 3 cm² at gestational age of 16+1). Detailed sonographic examination at 20 weeks of gestation showed no structural abnormalities in the normal twin and a normal amount of amniotic fluid. Follow-up visits were conducted every other week. Normal interval fetal growth was documented until the 30^th week of gestation. The fetus was small (less than the 5^th percentile) but showed balanced growth with normal amniotic fluid volume. Antenatal fetal evaluations were done every week after the 30^th week of gestation. Serial umbilical artery Doppler findings showed upper normal values (SD ratio 3.0–4.0). At gestational age of 35+6, a decreased fetal heart rate with variability and occasional decelerations were detected on electronic fetal monitoring. Delivery was performed by emergency cesarean section on the same day and a female infant was born weighing 1810 g with Apgar scores of 2 and 5 at 1 and 5 min, respectively. On examination of the newborn, no structural abnormalities were detected. Pathological examinations of the placenta and the cord were performed. Placental size was 13.0×9.0×3.5 cm and showed focal placental infarctions. No evidence of chorioamnionitis and villitis was detected. The newborn was healthy except for delayed closure of the ductus arteriosus. The baby was discharged 14 days after birth without complication.

Figure 1

Three-dimensional ultrasonographic picture at gestational age of 7+5 showing a monochorionic diamniotic twin pregnancy. Crown rump lengths of larger twin (T1) and smaller twin (T2) were 9.3 mm and 4.4 mm, respectively. The twins had different heart rates.

Figure 2

Normal anatomy was evident in the larger twin (T1). In the smaller twin (T2), poor development of the upper extremities and cystic change in the trunk with relatively well-preserved lower extremities was noted.

Figure 3

Color Doppler image at gestational age of 10+5 showing a feeding vessel to the acardiac member. Arrow indicates radiofrequency ablation point.

Discussion

The perinatal mortality rate of a pump twin is approximately 55% if untreated [4]. A systematic review of the literature showed a pump twin survival rate of up to 85% with modern minimally-invasive techniques for cord occlusion or interruption of anastomosis [1, 5, 6]. The optimal gestational age for the procedure is still controversial. Some authors advocate early prophylactic treatment of all acardiac twins at approximately 16 weeks if reversed blood flow is demonstrated [2]. Treatment at this early stage would also avoid the difficulty associated with stopping blood flow that occurs with larger and sometimes hydropic acardiac twins. By contrast, Sullivan et al. advocate watchful waiting as the best initial management [5]. Action becomes more urgent as serial ultrasound examinations reveal increasing growth of the acardiac twin as the circulatory burden on the pump twin increases accordingly.

Intrafetal RFA has been reported to be an uncomplicated and effective treatment when compared with other methods [3, 6]. RFA has been associated with lower rates of premature delivery and rupture of membranes before 32 weeks of gestation (23% vs. 58% for other techniques), and a higher rate of clinical success than with cord occlusion techniques [6]. In a review by Tsao et al. on RFA, intrafetal RFA for an acardiac twin was performed using 14 G RFA needles at an average age of 21 weeks of gestation (range 17–24 weeks) [7]. In a more recent review by Paolo et al., intrafetal RFA was done by a 17 G needle at an average gestational age of 21+5 (range 14–23 weeks) [1].

In the present case, we used a 20 G RFA needle that was originally designed for peripheral nerve ablation in neurosurgery. We successfully treated the acardiac twin using RFA on the communicating vessel at a gestational age of 11+6, possibly the earliest stage at which this type of procedure has been performed.

Early RFA might have some advantages over the conventional intrafetal RFA. Late first trimester (gestational age of 11+0 to 13+6) is the proper time for simultaneously measuring nuchal translucency, Doppler assessment, karyotyping, and treatment of TRAP sequences. Early RFA uses a small caliber needle, which makes the procedure safer and less painful. With the exception of sensitive pregnant women, we do not typically use local anesthetics with the 20 G needle. Early RFA can be done in a short time period due to the small caliber of the communicating vessel. In addition, it can be done through the placenta without breaking the fetal membranes. As iatrogenic amniotic puncture with a relatively thick needle is unavoidable in intrafetal RFA, the overall incidence of premature preterm rupture of membranes had been reported to be at least 22% in a literature review, making it the most common complication related to RFA [1]. A recent case series reported by Paolo et al. using a 17 G needle showed 57% incidence of premature preterm rupture of membranes after RFA [1].

RFA could have been performed even earlier in our case. However, we were concerned that it might affect placental growth and the developing embryo. After 12 months of follow-up, the newborn showed normal growth and development. In conclusion, if vascular anastomosis is seen on the placental surface on ultrasound/Doppler examination, early vascular RFA can be an easy and safe option compared with intrafetal RFA.