Prenatal diagnosis of congenital heart defects in thoracoabdominally conjoined twins

Twenty-five years of fetal echocardiography in conjoined twins: lessons learned

BACKGROUND

The aim of this study was to determine the accuracy of prenatal echocardiography in the diagnosis of intracardiac malformations and the degree of cardiac fusion in conjoined twins presenting to a single center over a 25-year period.

METHODS

The study group included 53 sets of conjoined twins from 1987 to 2012, including 38 thoracopagus, six parapagus, six omphalo-ischiopagus, two omphalopagus, and one cephalopagus. Twins were classified according to the degree of cardiac fusion: separate hearts and pericardium (group A, n = 10), separated hearts and common pericardium (group B, n = 2), fused atria and separated ventricles (group C, n = 2), and fused atria and ventricles (group D, n = 39). Postmortem examination was possible in 68 individual cases (98 deaths [69.3%]).

RESULTS

Cardiac defects were diagnosed in 47 sets of twins (88.6%). In 10 (18.8%), only one fetus was affected, and in 37 (69.8%), both fetuses were affected (n = 84/106 [79.2%]). There was a high predominance of right-sided lesions (63.0% [53 fetuses in 84 affected]) including pulmonary atresia or stenosis (35.7%), tricuspid atresia (11.9%), and hypoplastic or small right ventricle (21.4%). Autopsy findings added information to fetal echocardiographic findings in nine sets of twins (25.7%). Three pairs classified antenatally in groups A, B, and D were confirmed by autopsy in groups B, C, and C, respectively.

CONCLUSIONS

This study demonstrates that specialized fetal echocardiography is not a perfect diagnostic tool but is sensitive enough to establish prognosis in the counseling process. Because of complexity, such evaluations should be performed only at tertiary centers by specialists who are familiar with the peculiarities of this rare malformation. The predominance of right-sided lesions is not only an interesting finding, but this information has essential importance in terms of shortening examination times, allowing a more focused analysis of the fetal heart.

Various modalities for evaluation of a fused heart in conjoined twins

Conjoined twins are a rare congenital anomaly with an estimated incidence of 1/50,000 to 1/100,000. Among thoracopagus conjoined twins, 75% have a fused heart. We compare the usefulness of various modalities for evaluating cardiovascular structure in fused-heart conjoined twins. We report a series of 20 sets of thoracopagus conjoined twins as well as the results of a PubMed database literature review literature from 1982 to 2009. Twenty sets of fused-heart thoracopagus conjoined twins were evaluated by echocardiography, cardiac catheterization, magnetic resonance image (MRI), and three-dimensional computed tomography angiography (3D-CTA). Imaging results were compared to findings at surgery or autopsy. All sets of conjoined twins underwent postnatal echocardiography; 11 sets (55%) underwent cardiac catheterization; 4 sets (20%) underwent MRI; and 1 set (5%) underwent 3D-CTA. All intracardiac anatomy (ICA) was identified by echocardiography. Cardiac catheterization, MRI, and 3D-CTA were able to identify extracardiac vascular structures as well as the ICA. 3D-CTA, which can be performed as early as the first week of life, is a noninvasive, less expensive, and the safe examination with minimal risk due to its short procedural time. Three-dimensional CTA is an effective and safe modality for evaluating the cardiovascular anatomy of fused-heart conjoined twins before surgery.

Heteropagus (parasitic) twins: a review

Heteropagus, or "parasitic," twins are asymmetric conjoined twins in which the tissues of a severely defective twin (parasite) are dependent on the cardiovascular system of the other, largely intact twin (autosite) for survival. The estimated incidence of heteropagus twins is approximately 1 per 1 million live births. Isolated case reports comprise most of published work on this rare congenital anomaly. In the past, review articles have focused narrowly on one particular anatomical subtype of parasitic twin and/or on the anatomicopathology observed. Here, we present the epidemiology, proposed pathoembryogenic origins, anatomical abnormalities, management, and outcomes of the wide array of heteropagus twins described in the English language literature.

Prenatal sonographic delineation of the complex cardiac anatomy of thoraco-omphalopagus twins

We describe a case of thoraco-omphalopagus twins diagnosed at 18 weeks' gestation. Each twin had a separate set of anatomical structures except for a shared heart, upper liver and anterior chest wall. The heart was located at the center of the juncture, and consisted of three atria and two ventricles, each twin having a single ventricle and right atrium but a fused left atrium. A set of great arteries originated from each single ventricle and there was juxtaposition of the aortic and pulmonary valves. One twin had transposition of the great arteries, whereas in the other these were normal in configuration. There was only one umbilical cord which contained four vessels (two arteries and two veins). This case report demonstrates the possibility of using fetal echocardiography to delineate the cardiovascular complex of the conjoined heart.

Imaging in the preoperative assessment of conjoined twins

Conjoined twins are rare and present a unique challenge to pediatric surgeons and radiologists. Planning of surgical separation is aided by accurate preoperative imaging. Such twins are classified according to the most prominent site of connection: the thorax (thoracopagus), abdomen (omphalopagus), sacrum (pygopagus), pelvis (ischiopagus), skull (craniopagus), face (cephalopagus), or back (rachipagus). The area of fusion largely determines the imaging modalities used. Thoracic conjunction is most common and requires cardiac assessment. Magnetic resonance imaging and computed tomography provide excellent anatomic and bone detail, demonstrating organ position, shared viscera, and limited vascular anatomy. Contrast material radiography allows evaluation of the gastrointestinal and urogenital tracts, and a shared liver requires assessment of anatomy, vascularization, and biliary drainage. Angiography helps define specific vascular supply, which is useful in determining the distribution of shared structures between the twins at surgery. Each set of conjoined twins is unique. An imaging strategy to accurately define anatomic fusion, vascular anomalies, and other associated abnormalities is important for surgical planning and prognostic information.

Cardiac catheterization in diagnosis and management of congenital heart disease in thoracopagus conjoined twins

Over the last two decades, surgical separation of thoracopagus conjoined twins has become increasingly feasible. Delineation of the degree of cardiac involvement is essential to establish the feasibility of surgical separation. We describe our experience of cardiac catheterization both in the diagnosis and management of nine sets of thoracopagus twins who presented to a single center over three decades and discuss its role in conjunction with other modern diagnostic modalities.

Surgical ligation of a persistent arterial duct in one of conjoined thoracopagus twins prior to surgical separation

One of conjoined thoracopagus twins, with separate hearts and a common pericardial sack, presented with respiratory distress because of a persistent arterial duct causing congestive heart failure in the neonatal period. Surgical ligation of the duct was performed prior to subsequent separation, with an excellent outcome.

Utilization of magnetic resonance imaging in autopsy planning with specimen preservation for thoraco-omphalopagus symmetricus conjoined twins

Conjoined twinning is a rare obstetric event that has fascinated physicians and laypersons alike for centuries. When this event occurs, early diagnosis, close prenatal management, and the proper route of delivery will assure the best possible outcome for mother and affected infants. Magnetic resonance imaging (MRI) is used both as an ancillary technique to the sonography for the antepartum diagnosis and in the preoperative planning for the surgical separation of conjoined twins. This report describes the MRI findings in conjoined twins of the thoraco-omphalopagus symmetricus type, a condition incompatible with extrauterine life. The twins were delivered at 21 weeks gestation. The MRI was used to evaluate the anatomic nature of the internal anomalies. These findings were then used to develop an autopsy approach plan that preserved the external phenotype. After dissection, the specimen was preserved by using polyethylene glycol and ultimately prepared for use as a teaching specimen.

Anaesthetic management of the surgical separation of a pair of thoracopagus-cardiopagus twins

We describe the anaesthetic management of the surgical separation of a pair of thoracopagus-cardiopagus twins with a common right atrium and a myocardial tissue bridge containing vascular channels between their ventricles. One of them died during the procedure, the surviving twin is now two years old. The survival of one twin for two years without significant sequelae, after the surgical separation of twins with shared right atrium and fused ventricles, has not previously been reported. Careful preoperative assessment is essential to anticipate potential serious problems during the procedure.

Definition of inseparably fused ventricular myocardium in thoracopagus: fetal echocardiographic utility and pathologic refinement

Correlative echocardiographic and pathological findings in a thoracopagus with conjoined hearts are reported. One twin had tricuspid atresia with discordant atrioventricular connections and concordant ventriculoarterial connections. The morphologic right ventricle was hypoplastic and there was a large muscular ventricular septal defect. The other twin had hypoplasia of the mitral valve anulus and left ventricle with double-outlet right ventricle and pulmonary valve atresia. The tricuspid valve was severely insufficient in part because of a large orifice and redundant, elongated leaflets with abnormal chordal attachments. The left ventricles of these two twins shared a perforated common "free wall" with at least two large defects allowing mixing of the circulations at that level. Not all anatomic details were established conclusively by fetal echocardiography; however, sufficient diagnostic information was obtained to support a decision not to aggressively resuscitate these twins after elective cesarean delivery at 31 weeks' gestation.

Sonographic prenatal diagnosis of congenital heart defects in thoraco-omphalopagus

Thoraco-omphalopagus is the most common variety of conjoined twins. About 90% of the conjoined thoraco-omphalopagus twins have a common pericardium, and 75% have conjoined hearts. Options for the treatment of thoraco-omphalopagus are largely dependent on the anatomy of the cardiovascular system. The extent of the conjunction of the heart and the severity of the associated cardiac defects primarily determine the feasibility of successful separation of the infants. Two-dimensional echocardiography and color Doppler examination has become the method used to investigate cardiovascular system of conjoined twins with a high degree of confidence. A case of thoraco-omphalopagus conjoined twins prenatally determined of the extent of cardiac conjunction and diagnosis of associated defects by these methods is presented.

Morphology of the cardiovascular system in conjoined twins: spatial and sequential segmental arrangements in 36 cases

Thirty-six pairs of conjoined twins are reviewed from the joint experience of the authors. The external forms of conjunctions were 18 thoracopagus (joined at chest), eight cephalothoracopagus (joined at head and chest), eight dicephalus (single trunk and two heads), one craniopagus (joined at head), and one omphalopagus (joined at abdomen). There was one case with a single conventional heart in association with isomerism of the left lungs and absence of the heart in the left-side twin. Six cases had two conventional hearts. All of them had associated lesions, which were more severe in three cases (50%) with abnormal laterality. All of the cephalothoracopagus (eight cases) had two shared hearts. Cardiac lesions were commonly seen in the posterior heart, but the arrangement of atrial appendages were normal in every heart. Twenty-one cases of either dicephalus or thoracopagus had a compound heart. Three cases (14%) had fusion only at the level of venous sinus; three others (14%) were fused at the atrial level only, but 15 cases (71%) had fusion at both atrial and ventricular levels. Abnormal laterality was an associated lesion in ten cases (48%) with a compound heart. The fusion at the atrial level always occurred between right atriums, but ventricular fusion was more commonly between two left ventricles. Four atrial or ventricular chambers, if fused, were arranged in a cruciate arrangement. Mode of conjunction was as important, in the formation of the cardiovascular system, as was the degree of fusion. Abnormal laterality, which is commonly associated in lateral or mixed lateral/facing conjunction, was the most important factor affecting the general morphology of the cardiovascular system.

Conjoined twins: medical, surgical and ethical challenges

Four sets of conjoined twins were reviewed. One set was of the omphalopagus type with no associated abnormalities and were successfully separated at 12 days of age. The other three were of the thoracoomphalopagus type with major cardiac and other abnormalities, they were not amenable to surgery and did not survive. Conjoined twins require precise clinical and radiological evaluation. Many factors contribute to the management of such twins and ethical issues must be considered before surgical separation is undertaken.

Ultrasonographic prenatal diagnosis of conjoined thoracopagus twins: a case report

A case of prenatal diagnosed thoracopagus conjoined twins is presented. In thoracopagus twins the cardiovascular system mainly determines the options for separation and survival. Therefore prenatal investigation of this organ system is indispensable. Ultrasound level-2 examination predicted the impossibility of separation and fully matched the autopsy findings. In conclusion, ultrasound examination appears to be an important tool to enable planning of the optimal delivery approach.

Ischiopagus tetrapus twins: urological aspects of separation and 10-year followup

Conjoined twins occur once in 50,000 births. Only 6% of conjoined twins are of the ischiopagus type in which the twins are joined symmetrically at the pelvis and fusion begins at the level of the common umbilicus. The longitudinal axis extends in a straight line in opposite directions and the genitourinary and gastrointestinal tracts are shared. Tetrapus is a subtype in which all 4 lower extremities are present and oriented at right angles to the axis of the common trunk. Two sets of female ischiopagus tetrapus twins were born in 1977 and successfully separated at the St. Louis Children's Hospital in the following year. We describe the genitourinary and associated anomalies, surgical separation and long-term urological followup of these 2 sets of ischiopagus tetrapus twins.

Anatomic findings in dicephalic conjoined twins: implications for morphogenesis

The morphogenesis of conjoined twins is incompletely understood. We therefore conducted a postmortem study of dicephalus dibrachii dipus conjoined twins. The twins were born without pertinent history or prenatal diagnosis at 38 weeks and lived for several hours. External genitalia were female and partly duplicated; a caudal appendage was present in the thoracolumbar region. The heart and liver were shared and exhibited major abnormalities in configuration. Four lungs, three kidneys and adrenal glands, and two spleens were identified; biliary and upper gastrointestinal tracts appeared as mirror images. From these findings, we postulate three major sets of consequences arising from the anatomical disposition of the twin notochords ("paleoaxes"). 1) The degree of convergence/divergence of craniocaudal paleoaxes is variable. Convergences are maximal in the upper thoracic and sacral regions, where duplication of organs in minimal because of interaction aplasia. 2) In the horizontal plane, paleoaxes are sufficiently divergent to produce a degree of twin expression posteriorly, whereas anteriorly they converge to form a single, anterior, midline "neoaxis." Interposed between these zones of paleoaxial and neoaxial expression are areas of variable interaction aplasia. 3) The left twin was in situs solitus; the right twin was in situs inversus in a manner resembling polysplenia.

Surgical experience with thirteen conjoined twins

Conjoined twins occur in approximately one in 50,000 or so births, and most do not survive. The authors report herein their experience with 13 conjoined twins over the last 30 years, involving those of the following forms: thoracopagus (4 cases), omphalopagus (1 case), ischiopagus (4 cases), pygopagus (1 case), craniopagus (1 case), and incomplete or parasitic varieties (2 cases). The various diagnostic and imaging studies used are described in detail for each form of twinning. Separation is best delayed until such infants are relatively mature (i.e., 6-12 months of age). Operative survival was 50% in those operated on in the neonatal period, but 90% in those over 4 months of age. Ten separations were attempted in 13 sets of twins, with 16 operative survivors. Significantly, up to 10 years after surgery, there were six late deaths due to serious associated congenital anomalies, predominantly cardiac. Improved recent survival is probably the result of the availability of more accurate imaging studies and better anesthetic and operative techniques, with great emphasis on performing immediate reconstruction whenever possible. Use of skin expanders and prosthetic mesh has facilitated wound closure. In the future, ex vivo cardiac reconstruction and autotransplantation may permit separation of twins with complicated conjoined hearts.

Magnetic resonance imaging and ultrasonography in the antenatal evaluation of conjoined twins

Magnetic resonance imaging and sonography were used as diagnostic aids in the antepartum evaluation of two sets of conjoined twins. Magnetic resonance imaging was performed at 20 weeks' estimated gestational age on thoracopagus/omphalopagus twins and on omphalopagus twins at 20 and 30 weeks. Magnetic resonance imaging is a complementary adjunct to ultrasonography and provides additional anatomically precise clinical data. The advantages of this noninvasive technique include a large diagnostic window allowing total fetal imaging with excellent resolution of tissue composition. Unlike computerized tomographic imaging, there is no associated radiation exposure. The principal disadvantages of magnetic resonance imaging at this time are the cost of the equipment and the lack of real-time imaging capability.

Congenital heart disease and extracardiac anomalies: associations and indications for fetal echocardiography

Fetal echocardiography is a well-established technique for the prenatal identification of congenital heart disease. One of the indications for its use is the presence of extracardiac anomalies, as such coexistent defects may have important implications for obstetric and neonatal management. We have reviewed the obstetric and pediatric literature to examine reported associations. If a fetus is suspected to have hydrocephalus, microcephaly, holoprosencephaly, agenesis of the corpus callosum, Meckel-Gruber syndrome, esophageal atresia, duodenal atresia, diaphragmatic hernia, omphalocele, or renal dysplasia, cardiac evaluation should be pursued. Furthermore, echocardiography may be of help in differential diagnosis of some anomalies (for instance, skeletal dysplasias). Maternal diabetes and phenylketonuria, as well as exposure to phenytoin, trimethadione, or isotretinoin, may result in multiple systemic defects, including congenital heart disease.