A Case Study : Acardiac Twin (Acardius anceps) Dr. Lavina Chaubey (Dept. of Obgyn), Dr. Madhu Jain (Dept. of Obgyn), Dr. Ashish Verma (Dept. of Radiology), Dr. Shivi Jain (Dept. of Radiology) Institute Of Medical Sciences, Banaras Hindu University, Varanasi (U.P.), India BACKGROUND • • Twin Reversed Arterial Perfusion sequence (TRAP) is a complication of monochorionic twin pregnancy in which one twin with an absent or nonfunctioning heart e.i. non-viable acardiac twin is perfused by the other “pump” twin via placental artery to artery anastomoses resulting in growth and the characteristic anomalies of the acardiac twin with possible heart failure of the pump twin. TRAP sequence occurs in about 1% of monochorionic pregnancies and 1 in 35,000 deliveries • • • CASE HISTORY • • • • • • • • • • • • A 25 year old second gravida (previous 1 spontaneous abortion of 1 month gestation) was booked for antenatal care during current pregnancy from 6 weeks of gestation LMP 21/09/2012, EDD 28/06/2013 ,previous cycles normal and regular Patient had an ultrasound from a private centre showing a single live intra-uterine pregnancy of 6+3 weeks with CRL 6.4 and +ve cardiac activity Past history Family history Revealed Personal history no abnormality General examination Baseline antenatal investigations In the first trimester of her current pregnancy, patient had a single episode of mild antepartum haemorrhage Serial ultrasounds showed monochorionic diamniotic twin pregnancy with one live twin at 12+6 weeks , liquor adequate and another twin of 10 weeks with no cardiac activity. Placenta was left anterolateral reaching upto the margin of the os. A subchorionic bleed of 2.7 x 0.7 cm was noted at the placental margin located over the os . Cervical length was 4.1 cm with no evidence of funneling. Subsequently, the subchorionic bleed was seen to be resolving and the live pregnancy progressing. Follow up MRI showed monochorionic pregnancy with a live twin having normal biometric parameters corresponding to gestational age of 17+0 weeks. Amniotic fluid was normal and heart rate 132 bpm. No abnormality , structural or otherwise, was seen. Twin 2, however, was hydropic with malformations. The femur was present with a length of 1.82 cm corresponding to a GA of 15+3 weeks.The brain showed multiple cysts. Abdominal and thoracic organs could not be delineated at all. A primitive looking heart tube and aortic arch were present. Pulsations from the area could be seen with a rate of 139 bpm (difference of <10 bpm from the first twin) Placenta was single with inter-placental venous lakes. The lower segment was free. An intertwinning membrane could be seen Color Doppler of the normal twin (first) showed a four chambered view of the heart with high amplitude triphasic arterial waveform from the cardiac area and a normal flow. But the hydropic twin(second) showed only a tubular heart and low amplitude attenuated waveform, possibly arterial, which at the time was thought to be originating from the heart. A provisional diagnosis of monochorionic twin pregnancy with twin 1 normal and twin 2 grossly malformed , both live, was made at the time based on the reports of USG, MRI and color doppler (doppler scan of the placental circulation was not done since the abnormal twin was thought to be live). • Leading twin (acardius) being delivered at caesarean section( thin arrow) followed by after-coming sac of normal twin ( thick arrow) Acardius anceps with head (thick arrow), meningomyelocoele (thin arrow) and lower limb bud Normal twin being delivered at caesarean section after the abnormal one (thick arrow) Front view of abnormal fetus showing attachment of the cord • Normal Twin Abnormal Twin • Visible vascular anastomoses between the two cords on placental surface (thick arrow) • • • • • • The pregnancy was followed under close supervision and it proceeded uneventfully. However, only one fetal heart could be heard at a time clinically. At 28 weeks, patient reported to labour room with pain abdomen. She was found to be in labour with the abnormal twin leading. However, it’s presentation or heart rate could not be determined . The normal twin was smaller, transverse and having a heart rate of 136 bpm. Due to failed progress of labour patient was shifted for emergency caesarean section Twin 1 (1070 gms) was dead, grossly malformed (acardiac twin) Twin 2 (910 gms/F) was apparently normal, APGAR 5/10, 6/10 and had to be resuscitated. She was shifted to NICU where she was put on mechanical ventilation, surfactants and I/V antibiotics. However the baby developed refractory shock and died on day 3 of life due to complications of prematurity. Placenta was single with close insertion of the two cords and visible anastomoses in between. • Vascular connection between two cords being cut open From there, the ductus venosus shunts 80 percent of the placental blood flow into the inferior vena cava, where it mixes with venous return from the lower extremities and kidneys before entering the right atrium. Once the blood enters the right atrium, the two sides of the fetal heart act in parallel through intra- and extra-cardiac shunts (foramen ovale, ductus arteriosus) to fill the aorta and provide systemic circulation. The distal aorta terminates in the left and right common iliac arteries, which each divide into internal and external iliac branches. The umbilical arteries carry blood from the internal iliac arteries back to the placenta. In TRAP sequence, the pump twin maintains this normal pattern of fetal circulation. In addition, a portion of its cardiac output travels through placental arterial-arterial anastomoses to the umbilical artery and eventually the systemic circulation of the recipient co-twin, thus creating “reversed” circulation in this twin. This is possible because the acardiac twin lacks a functional heart, whose pumping would normally provide forward flow and high systemic pressure. The presence of placental vascular anastomoses is common in monochorionic twins and alone is not sufficient for the development of TRAP sequence. The abnormal circulatory pattern provides perfusion of deoxygenated blood from the pump twin to the lower half of the recipient twin via its iliac arteries, but poor perfusion of the upper torso and head. Unequal vascular perfusion from the pump twin may contribute to the evolution of a variety of structural abnormalities in the recipient twin. The acardiac twin has been classified according to the degree of abnormal development. The most common anomaly is acardiac acephalus, in which the fetal thoracic organs and head are absent. Other rarer types are acardius acormus, in which only the fetal head develops; acardius amorphus, consisting of a shapeless mass of tissue with no recognizable human parts; and acardius myelacephalus, in which the head and one or more extremities are partially developed. CONCLUSION • • Communicating channel between the two cords showing blood clot AP and Lateral view of x-ray of acardiac twin DISCUSSION • • • Acardia was first described in the sixteenth century referred to as chorioangiopagus parasiticus It is the most extreme form of twin to twin transfusion syndrome now referred to as twin reversed arterial perfusion sequence. In the normal fetal circulation, blood from the placenta flows through the umbilical vein to the fetus. • • • • This was a case of acardiac twin pregnancy which was missed in the antenatal period due to erroneous finding of pulsations in the cardiac area of the abnormal twin The pulsation and abnormal waveform from the cardiac area of the abnormal twin on doppler was probably the transmitted wave from the heart of the normal twin. It became attenuated because of the long distance it travelled retrograde through the circulation of the acardiac fetus The abnormal twin is acardiac anceps ( most developed among all) since the x-ray shows the presence of the skull, vertebral column, ribs, lower limbs The upper limbs were not formed Brain was replaced by cystic spaces as seen on the ultrasound. Thoracic and abdominal organs could not be delineated.
© Copyright 2024 ExpyDoc