The acardiac twin. A case report

The acardiac twin is a rare consequence of monozygotic twinning and occurs in 1 per 35,000 deliveries. One percent of all monozygotic twins is affected. Prenatal diagnosis is possible with ultrasonography. Complications associated with the presence of an acardiac twin include sequelae from the twin-to-twin transfusion syndrome, polyhydramnios, dystocia, ruptured uterus and congestive heart failure in the normal twin. In utero fetal therapy is possible in some instances.     

Pathogenesis of acardiac twinning: clues from an almost acardiac twin

OBJECTIVE: To search for clues to the pathogenesis of acardiac twinning. METHODS: We examined a case of monoamniotic twins in which twin A's only sonographic abnormality was a dilated, tortuous ductus venosus. Twin B also had this abnormality as well as multiple other anomalies that included enormous hydrops and a severely hypoplastic heart. Following termination of pregnancy, autopsy was performed. RESULTS: Postmortem examination of the placenta confirmed monochorionic, monoamniotic placentation with two adjacent trivascular cords. Autopsy confirmed the sonographic findings of enormous hydrops in twin B with a severely malformed, almost nonexistent heart. In addition, the liver was small and was represented by a cyst-like structure with thin rims of congested parenchyma surrounding large vascular spaces. CONCLUSION: We believe the sequence of events in this case was early twin-to-twin transfusion resulting in a dysfunctional heart in twin B. This enabled a twin reversal arterial perfusion sequence with further deterioration of twin B's heart and extreme congestion of deoxygenated blood exiting the heart into the inferior vena cava and ductus venosus. This case supports the concept that circulatory reversal in the face of an initially functioning heart may lead to congestion, tissue hypoxia and secondary organ atrophy.     

Percutaneous ultrasonographically guided ablation of an acardiac twin

Acardiac twinning is caused by twin reversed arterial perfusion (TRAP). Normal "pump" twins may face early delivery and cardiac decompensation and have a high perinatal mortality. A primagravid patient had serial evaluation of a TRAP pregnancy beginning early in the second trimester. Rapid growth of the acardiac sibling, high diastolic velocity Doppler waveforms in the perfusing vessel, and early hydramnios prompted ablation of blood flow by a percutaneous ultrasonographically guided infusion of absolute alcohol. A term birth of a normal pump twin was the outcome. Ablation of blood flow into an acardiac sibling of a TRAP pregnancy may be indicated in cases with a poor prognosis by use of an effective percutaneous ultrasonographically guided technique.     

Antenatal diagnosis of acardiac, acephalic twin

A case of acardiac, acephalic twin diagnosed by antenatal ultrasound is reported. The obstetrical significance of this condition is discussed.     

Prognostic markers in twin pregnancies with an acardiac fetus.

OBJECTIVE: With twin reversed arterial perfusion sequence, the normal cotwin is at risk of heart failure. The purpose of this study was to identify ultrasonographic variables that can help predict prognosis. We hypothesized that variables reflecting the hyperdynamic circulatory condition of the normal fetus and the changes in circulatory impedance in the acardiac mass would correlate with final outcome. METHODS: Ten twin pregnancies with this condition were identified. Follow-up was available for nine. Adverse outcome was defined as death, cardiac failure, or delivery before 30 weeks' gestation for reasons related to the presence of the mass. The following data were collected on the normal fetus: cardiothoracic ratio and left ventricular shortening fraction; and on the mass: maximal length, presence and size of cysts, and presence of a rudimentary heart. The pulsatility index (PI) of the umbilical arteries (UA) of both twins was measured. RESULTS: Four fetuses died, two in utero (22 weeks) and two after cesarean (26 and 31 weeks) for advanced cardiac failure. In the five other cases, the outcome was favorable. The cardiothoracic ratio and presence of cysts or of a rudimentary heart did not correlate with outcome. A PI in the mass' UA significantly lower than that of the normal twin (ratio of 0.71 compared with 1.04 for good outcome, P<.05), an elevated shortening fraction in the second trimester, and a rapid growth rate of the mass were associated with a poor prognosis. CONCLUSION: In pregnancies with twin reversed arterial perfusion sequence, final outcome and treatment decisions can be determined based on hemodynamic criteria.     

Documentation of paradoxical umbilical blood supply of an acardiac twin in the antepartum state

In a case with one acardiac twin, color Doppler examination revealed retrograde umbilical circulation to this fetus. This pulsatile flow in the umbilical vessel of the acardiac fetus was supported by the cardiac function of the co-existing healthy twin.     

Kallmann syndrome: a case of twin pregnancy and review of the literature

In order to evaluate the possibilities for induction of ovulation, the functional competence of the pituitary gland of a woman with Kallmann syndrome was examined by two consecutive dynamic GnRH tests. The second test was conducted after 1 week's treatment by a GnRH pump. The results, which showed some rise of LH but no response of FSH, favored induction by hMG/hCG therapy. Three treatment cycles resulted in a twin pregnancy which was normal and was carried to term. Review of the literature shows only six previously reported pregnancies in women with Kallmann syndrome. Five of them were treated by hMG/hCG, and one by pulsatile GnRH. The two methods of induction are discussed in relation to the heterogeneity of the pituitary and ovarian function in Kallmann syndrome. We show that this heterogeneity dictates that the treatment for induction of ovulation should be individually adjusted according to the pituitary and ovarian competence.     

Intrauterine treatment for an acardiac twin with alcohol injection into the umbilical artery

An acardiac twin is a unique complication of monochorionic twinning, in which a normal pump twin perfuses the acardiac twin. The mortality rate of the pump twin is greater than 50%. Herein we present the successful treatment of an acardiac twin with alcoholization as follows. An acardiac twin was diagnosed at 24 weeks gestation. Circulation interruption of the acardiac twin was successfully achieved by injection of absolute alcohol (5 mL) into the intra-abdominal umbilical artery. Serial ultrasound after the procedure revealed normal growth of the pump twin, whereas the acardiac twin was shrinking. Spontaneous premature delivery at 34 weeks gestation resulted in a normal surviving female baby weighing 2410g and an acardiac female fetus weighing 300g. This experience suggests that this simple technique may be an alternative treatment for an acardiac twin.     

Successful intrauterine treatment with alcohol ablation in a case of acardiac twin pregnancy.

Acardiac twinning is a rare obstetric condition unique to monochorionic twin gestation and the pump twin has high perinatal mortality. We report an acardiac twin pregnancy, in which the pump twin presented with intrauterine growth restriction and oligohydramnios, and grossly hydropic acardiac fetus measured 12 x 14 x 18 cm, and with no cardiac activity at 27 weeks of gestation. We treated the acardiac fetus with 1 ml alcohol ablation in utero, and delivered a live male baby weighing 1750 g at 36 weeks' gestation.     

When does death occur in an acardiac twin? Ultrasound diagnostic difficulties

Fetal acardia is a rare abnormality of multiple pregnancies, which is lethal for the affected fetus and can cause death in 50% of normal co-twins. Antenatal recognition with early ultrasound is essential to institute a prospective management to improve the outcome. Our communication outline the difficulties which may be encountered in ultrasound diagnosis. In particular the problem of distinguishing a fetal heart from large pulsating mediastinal vessels, which can be present in these fetuses, and the difficulty of diagnosing death in an acardiac fetus. Our report confirms that the co-twin remains at increased risk of sudden death, even without ultrasound evidence of cardiac failure or biochemical compromise. The finding in this fetus of intravascular fibrin deposits suggests the possibility of acute disseminated intravascular coagulation, not previously reported in association with an acardiac twin.     

Selective reduction of acardiac twin by radiofrequency ablation

OBJECTIVE: Acardiac/acephalic twinning is a rare anomaly in which a normal "pump" twin perfuses an acardiac twin, which results in twin reversed arterial perfusion sequence. A novel technique for selective reduction and obliteration of blood flow in the acardiac twin is described. STUDY DESIGN: Thirteen consecutive cases of monochorionic twin gestation with twin reversed arterial perfusion sequence underwent selective reduction of the abnormal twin with the use of radiofrequency ablation. Under direct real-time sonographic guidance, a 3-mm (14-gauge) radiofrequency ablation needle was percutaneously inserted through the maternal abdominal wall into the intrauterine fetal abdomen at the level of the cord insertion site of the acardiac twin. Energy was applied until termination of blood flow to the acardiac fetus was documented by Doppler ultrasound scanning. RESULTS: All 13 mothers tolerated the procedure without major complications. All 13 "pump" fetuses have been delivered. Twelve of 13 infants are alive and well. The first patient in this series was delivered at 24.4 weeks and the infant subsequently died from complications of prematurity. Average gestational age at intervention was 20.7 weeks, and the average gestational age at delivery was 36.2 weeks. CONCLUSION: Radiofrequency ablation is a minimally invasive, percutaneous technique that can effectively obliterate blood supply to an acardiac twin to preserve and protect the pump twin.     

Term birth after midtrimester hysterotomy and selective delivery of an acardiac twin.

OBJECTIVE: Our aim was to determine whether hysterotomy and selective removal of an acardiac twin could improve the outcome of the "pump" twin. STUDY DESIGN: A literature and case review of the outcome of the acardiac twin malformation was performed. When an acardiac malformation was diagnosed at 19 weeks' gestation the patient was monitored with weekly ultrasonographic examinations. At 23 weeks' gestation, no blood flow could be demonstrated to the acardiac twin and it was thought that the continued presence of the acardiac twin posed a risk to the "pump" twin. A midtrimester hysterotomy was performed and the acardiac twin was delivered. RESULTS: After the midtrimester hysterotomy, the pregnancy progressed to term and a healthy female infant was delivered by elective cesarean section at 37 weeks' gestation. CONCLUSION: Midtrimester hysterotomy may be a useful intervention in cases of twinning when one fetus is a threat to the health of the other.     

Prenatal and postnatal cardiologic evaluation of normal twin from acardiac twin pregnancy--case report

The aim of the paper was to describe dynamic changes in 'pump twin's' circulatory system within clinical observation, indication analysis for premature delivery due to cardiovascular findings and long-term postnatal follow up. In echocardiographic examination of 'pump twin' no structural heart defects but functional changes in cardiovascular system have been detected (cardiomegaly, right heart disproportion, tricuspid valve regurgitation). Within 10-week observation polyhydramnios did not increased significantly, no amnioreduction procedures had been performed. Due to single umbilical artery in 'pump twin' a cytogenetic examination had been performed revealing a normal karyotype. When the first signs of abnormal Doppler flows appeared such as increased PI of umbilical artery and DV and cardiomegaly with TR--caesarean section was performed at 33 weeks of gestation. Echocardiography performed in the first day of life findings: right atrium and ventricle enlargement, significant tricuspid valve regurgitation (V max 3 m/s), a prenatally undetected, small perimembrane-part ventricular septal defect. At the age of 6-months a non-significant VSD with tricuspid valve septal leaflet closure and ASD II has been confirmed. The infant is systematically followed-up by paediatricians, cardiologists and neurologists and her further neurodevelopment appears to be slightly retarded.     

Management of monoamniotic twin pregnancies: a case series and systematic review of the literature

Objectives To review the experience of the University of Toronto Perinatal Complex, Ontario, Canada concerning antenatally diagnosed monoamniotic twin pregnancies; and to compare our results with cases reported in the literature with respect to antenatal surveillance and perinatal outcome.
Methods A retrospective chart review of all twin gestations from 1993 to April 2000 was performed. A systematic review of the literature, 1966 to April 2000, of perinatal outcome in monoamniotic twin pregnancies was undertaken.
Setting All monoamniotic twin gestations at the University of Toronto.
Results Case-series: 25 prenatally diagnosed monoamniotic twin pregnancies were identified. Seven pregnancies were affected by fetal anomalies. One fetus died at 29 weeks. Neonatal complications occurred below 33 weeks of gestational age and were related to immaturity. Systematic review of the literature: 49 studies met our selection criteria and reported 88 cases diagnosed antenatally. Fourteen pregnancies were affected by major congenital anomalies. Twenty fetuses died after 24 weeks of gestation. Neonatal complications varied widely in severity and depended on gestational age at birth. The risk of intrauterine fetal death was 10% at the University of Toronto and 12% in the review of the literature.
Discussion Our experience, the largest so far, suggests that regular fetal surveillance and appropriate steroid administration leads to a good perinatal outcome. The risk of fetal death (10%–12%) is lower than the previously quoted risk of 30%–70%. A careful review of obstetric interventions and further work examining outpatient surveillance of monoamniotic twin pregnancies are needed. The best treatment of monoamniotic twin pregnancies can only be determined by randomised trials.     

Sonographic findings of acardiac twin in the first trimester of pregnancy

Twin Reversed Arterial Perfusion (TRAP) sequence, or the acardiac anomaly, is a rare complication of monozygotic twins, that occurs in approximately 1 in 35,000 births. In the first trimester, once the diagnosis of monochorionic twins is made, particularly if one embryo shows abnormal development or generalized edema, the TRAP sequence must be considered. Moreover, malformations reported in the perfused twin are often severe. Diagnosis is confirmed by using Doppler ultrasound which demonstrated the presence of retrograde perfusion in the umbilical cord of the abnormal twin. The more complete the body form is, the more similarity the vascular relationships have to the pattern found in a full-term fetus. Final outcome and treatment decisions can be determined based on hemodynamic criteria. We report a case of a misdiagnosed TRAP sequence with no structural malformations detected by ultrasonography at 12 weeks of gestation.