Twin Reversed Arterial Perfusion (TRAP) Sequence Case Study
Radiofrequency ablation (RFA) of blood supply to acephalic twin
The patient and her husband were of Brazilian origin and spoke only Portuguese, requiring the presence of a translator throughout their stay in our Center. She was a 24-year-old mother with two prior children who was referred at 17 1/2 weeks gestation because of a monochorionic, diamniotic twin gestation complicated by TRAP sequence.
Twin A was a typical acardiac/acephalic twin with massive diffuse soft tissue edema and an incompletely formed skeleton with no normal head structures, no normal stomach, kidneys or urinary bladder, and the absence of normal cardiac structures. An abnormal two-vessel umbilical cord with reverse arterial and venous flow was seen going to the abnormal twin. Twin B was structurally normal but had significantly increased amniotic fluid volume (polyhydramnios), and fetal echocardiography noted high-normal combined cardiac output due to the increased demands placed on the normal twin (pump twin) by the abnormal parabiotic twin.
When the volume of the acephalic twin was calculated, it was found to be 130 percent the size of the normal twin placing it in to a greater than 95 percent risk category for significant pregnancy complication. Pregnancy management options were discussed. They included termination of the pregnancy, continuation of the pregnancy without intervention allowing nature to follow its course with expectations of early delivery and possible cardiac complications in the pump twin, or interruption of the blood supply to the anomalous parabiotic twin using either bipolar cord cauterization or radiofrequency ablation of the blood supply. Selective bipolar cord cauterization is an accepted technique with a 95 percent pump twin survival and mean age of delivery of 36 weeks. However, RFA has emerged as a newer technique, which is significantly less invasive using only a 17-gauge (1.5 mm) needle devise and requiring only a 24-hour hospital stay. After careful consideration of their options, the family elected the RFA procedure.
Under epidural anesthesia a 3-mm skin incision was made, and with continuous ultrasound guidance, the RFA needle device was carefully directed to where the blood supply entered the abnormal parabiotic tissue mass. Radiofrequency ablation of the tissues and blood supply in this region was performed without complication. Color and power Doppler flow studies confirmed interruption of the blood supply to the abnormal fetus. The excess amniotic fluid volume was then removed (amnioreduction) from around the normal pump twin.
The patient was then transferred to labor and delivery at the Hospital of the University of Pennsylvania (HUP) where she was observed for four hours prior to being transferred to the high-risk obstetrics service. She received 24 hours of intravenous antibiotics and oral medication (indomethacin) to prevent preterm contractions. She was discharged from the hospital the following morning and remained at decreased activity at the Camden Ronald McDonald House for the next five days. Follow-up evaluation showed normal fluid around the pump twin, no blood flow to or within the parabiotic tissue mass, significant decreased fluid around the abnormal fetus and normal cardiac function in the surviving pump twin. She returned to her referring physician for ongoing pregnancy management. She is presently at 36 weeks gestation, has not yet delivered and her pregnancy is progressing normally.
Selective bipolar umbilical cord cautery and transection of anomalous parabiotic twin
The patient was a 33-year-old, second pregnancy, referred at 21 weeks gestational age for pregnancy complicated by a monochorionic, monoamniotic (single shared placenta, single shared amniotic sac) twin pregnancy, with one twin reported to have multiple congenital anomalies.
High-resolution ultrasound confirmed monoamniotic twins. Twin A’s features were consistent with an anecephalic/acardiac parabiotic twin with an abnormal two-vessel umbilical cord and reverse arterial and venous perfusion. These features are consistent with TRAP sequence.
The co-twin was anatomically normal, and echocardiography showed normal heart structures and function with no significant elevation of cardiac output. However, as these fetuses shared a common amniotic sac, extensive entanglement of the umbilical cords throughout the mid-sections was seen placing both at high risk for intrauterine fetal demise.
The calculated weight ratio of the abnormal to normal twin was 90 percent, placing this pregnancy in the highest risk category for Twin Reversed Arterial Perfusion Sequence (TRAP sequence) in addition to the risks associated with the entangled umbilical cords. After multidisciplinary consultation, the family requested selective bipolar umbilical cord cauterization of the abnormal parabiotic twin with transection (cutting) of the cord to reduce the risks associated with co-twin cord entanglement.
Under epidural anesthesia, a 3-mm skin incision was made under continuous ultrasound guidance, and a 3-mm trocar sheath passed into the common amniotic cavity. Approximately 4 inches lateral to the trocar sheath, a small 1.2 mm needle sheath was also introduced into the amniotic cavity under ultrasound direction. The needle stylet was removed and a 1-mm fiber-optic micro endoscope was introduced into the needle sheath to allow direct visualization of the bipolar cord cauterization procedure.
A segment of the abnormal two-vessel cord was identified adjacent to the beginning of the cord entanglements. The two-vessel cord was cauterized in three locations approximately 1inch apart. Using color and power Doppler on ultrasound, complete occlusion of blood flow to the acardiac/acephalic twin was confirmed. Direct visualization using the micro endoscope also showed complete occlusion of the abnormal umbilical cord. The bipolar instrument was removed from the amniotic cavity, and a tiny endoscopic scissors introduced and guided to the operative site with ultrasound.
Under direct micro-endoscopic visualization, the middle of the three cauterization sites was cut to free the anomalous twin from the entangled cords. No bleeding was visualized from the cut ends of the abnormal cord. Antibiotics were then placed into the amniotic sac, and all of the instruments were removed.
The co-twin’s heart rate remained normal throughout the surgery. The patient was transferred to the Labor and Delivery ward at the Hospital University of Pennsylvania where she remained for 24 hours on intravenous medication (magnesium sulfate) to prevent preterm labor, as well as 24 hours of antibiotics to reduce the risk of infection. The following morning the intravenous medications were discontinued and she was started on an oral medication (nifedipine) to be taken four times daily to reduce the risk of pre-term labor. The following morning she was discharged from the hospital and remained at the Philadelphia Ronald McDonald House at bed rest.
Five days later she underwent sonographic evaluation that confirmed no secondary operative complications and significant decrease in the degree of umbilical cord entanglement. She returned home to her referring physician and had a normal prenatal course until 36 ½ weeks at which time she experienced spontaneous rupture of membranes and onset of labor. A 6 lb. 4 oz. infant male with APGAR scores of 8 and 9 at one and five minutes respectively, was delivered vaginally without complications and was discharged from the hospital ten days after birth. The child is now 5 years of age and is developmentally normal. Following delivery of the normal twin, a small, and shrunken tissue mass, which had previously been the parabiotic twin, was passed without difficulty just prior to delivery of the placenta.