CHD is the most common congenital malformation in China. Due to the increased number of pregnant women with an advanced maternal age, since the announcement of the two-child policy in 2016, there were about 360,000 children with CHD born in China in 2018. Fetal echocardiography is a reliable means to diagnose the fetal heart malformation. Identification of severely fatal CCHDs by fetal echocardiography is helpful for timely intrauterine interventions, postpartum cardiac surgery, and saving lives. However, the cardiovascular malformations in the fetuses with CCHD are quite complicated. At present, the observation of the fetal cardiovascular system is still limited, especially the abnormal circuit of blood vessels and their branches are difficult to be fully displayed, which affects the quality of diagnosis. Limited by the experience and spatial imagination, especially by the knowledge of the anatomical structure of various types of CCHD, various diagnostic medical sonographers have different understandings and screening skills of CCHD. The detailed, accurate diagnosis of CCHD by prenatal echocardiography remains a huge challenge. In addition, the prenatal diagnostic legal disputes caused by CCHD in China are rising year by year, reaching 20%, which greatly hinders the development of prenatal ultrasound. Theoretically, the solidified filler can fill the fetal heart cavity, micro blood vessels and main branches, fully display the integrity and three-dimensional structure of the fetal blood vessels, comprehensively observe the circuit, shape and position of the blood vessels, and directly display the relationship between the local and overall. Therefore, it is especially suitable for the complex congenital heart diseases with abnormal vascular routing, and can be used as a control index to analyze the causes of missed and misdiagnosis of fetal echocardiography (18.104.22.168). Our team obtained 20 perfect models through an improved casting method, which played an important role in feeding-back prenatal ultrasound details and guiding clinical teaching.
The microvessel tracheal casting technique can stereoscopically display the abnormalities of cardiovascular and tracheal branches of the CCHD fetuses, especially the mutual positional relationship and the complex spatial structure of the large-micro vessel malformations. Therefore, the detailed information provided by the casting technique can help to improve the accuracy of an echocardiography diagnosis of CCHD, thereby providing a virtual reality tool to conduct the simulated CCHD cognitive training for diagnostic medical sonographers. At the same time, the correctly restored CCHD cardiovascular models can also be used to establish a permanently stored database by computerized tomography technology for future 3D printing restorations and replications. Therefore, the rare CCHDs can be infinitely copied for various cardiac surgeons and obstetricians and gynecologists for future study. The authors successfully prepared 20 CCHD casts and found a total of 69 abnormalities, of which 7 cases were missed, and 18 cases were misdiagnosed by prenatal echocardiography, resulting in an accurate ultrasound diagnosis rate of 52.18%. Furthermore, these diagnostic results were found amongst the senior physicians/experts, which can be unimaginably low, if conducted by general medical sonographers. The detailed information of the casts perfectly explained some of the doubts in prenatal ultrasound images (17.20.21). CCMM can clearly exhibit the shape, size, location and orientation of the atria and ventricles, and it can also show the abnormal connections between the atria and ventricles. In addition, the cast can clearly display the atrial appendage morphology, trachea-bronchial branch structures, anomalous pulmonary venous return (APVR), abnormal superior and inferior vena cava, hepatic veins, and the double outlet of the right ventricle with transposition of great arteries, which are difficult to find with the prenatal ultrasound.
A traditional autopsy has always been regarded as the gold standard for verifying the prenatal diagnosis. However, from our 20 years extensive research and experience, there are many defects in the diagnosis of complex congenital heart disease in regional anatomy. For example, CCHD specimens are usually small and weigh less than 2 kg, which is easy to destroy the thoracic structure, and the variation of microvessels cannot be observed in detail. Each CCHD specimen is extremely precious. The traditional formalin immersion cannot perfectly reflect the cardiovascular morphology, which often leads to the shrinkage of the heart and eventually leads to damage. Our modified CCMM could more clearly, completely, and permanently display the spatial relationship of the aorta and its branches (including abnormal arteriovenous, trachea, and oesophagus). Therefore, this technology can improve the clinician’s and sonographer’s understanding of the spatial location of complex cardiovascular malformations and further reveal some “rare” vascular malformation paths. Additionally, it can also help develop and evaluate the more complicated 3D mathematical models of the fetal cardiovascular systems (22.23).
Abnormal ductus arteriosus: Our study suggests that the highest rate of prenatal misdiagnosis is abnormal ductus arteriosus, including abnormal ductus arteriosus connection, abnormal morphology with stenosis and absence of ductus arteriosus. In severe right heart system obstructive congenital heart disease, the reverse blood flow in the arterial duct occurs due to the need of perfusion of the pulmonary artery from the aorta to support the growth and development of the lung. The changes in blood flow direction and flow volume cause the ductus arteriosus to be distorted and narrow. When the ductus arteriosus is distorted, the winding blood flow signal from the aorta to a pulmonary artery can be displayed. Still, when it is too narrow, the blood flow is difficult to be displayed, so it is easy to be misdiagnosed as an absence. For example, ① In Case 20, the prenatal ultrasound was misdiagnosed as coarctation of the aorta (CoA) with descending aorta originated from the right ventricle, while the cast confirmed it was an interrupted aortic arch (IAA) with a descending aorta originated from the pulmonary artery, the abnormal connection of ductus arteriosus (pulmonary artery - ductus arteriosus - left common carotid artery), and aberrant left subclavian artery (Fig. 1 & Video 1.2.3). ② In Case 13, only the aortic coarctation was diagnosed by prenatal ultrasound, while the ductus arteriosus abnormal connections (LCCA-DA-PA) was confirmed by cast (Fig. 2).
Aberrant subclavian artery: Aberrant left subclavian artery is an abnormal branch of the aortic arch, which is common in the left aortic arch with aberrant right subclavian artery or right aortic arch with aberrant left subclavian artery. The diameter of the aortic branches in the fetal period is small, and the examiner is easy to miss the accurate diagnosis. Therefore, when the left ductus arteriosus with the right aortic arch appears in the examination, we should consider, whether there is an aberrant left subclavian artery, for example: In Case 10, the prenatal ultrasound only diagnosed DORV and PAS. Later, DORV with TGA, RAA with ALSA were confirmed by vascular casting. When the left ductus arteriosus with the left arch appeared, attention should be paid to, whether there is an aberrant right subclavian artery. The examiner should pay attention to the scanning of the three vessels-trachea (3V+ T view) view, and increase the use of Spatio-temporal image correlation to evaluate the spatial position relationship of micro blood vessels, which is helpful to clearly and stereoscopically display the aortic branches and their circuit that are difficult to be clearly displayed on the two-dimensional image view.
RAA increases the risk of associated cardiac defects regardless of laterality of the ductal arch. Concomitance of right ductus and right aortic arch was object of a recent meta-analysis(24). Since there are cases of RAA and ALSA in table 1, We believe that left ductal arch in RAA often occurs in cases with interrupted aortic arch with TGA or coarctation of the aorta wiht TGA after cast model re-analysis. The casting technique directly shows the ductal path, which is obviously very easy to assist in the diagnosis of ductal laterality. For example, Figure 1 and Figure 2, they all belong to LDA. The experimental materials of this study only include ABS or denture base powder , pigment, syringe, catheter, sodium hydroxide solution and sulfuric acid, which are all from clinical departments, pathology departments, stomatology departments in our hospital and affiliated University anatomy rooms. The cost of a mold is about 200 yuan($ 31.4). Because it does not involve commercial use, the hospital provides material support, so the casting procedure is basically free, Casting cannot replace standard anatomy because some details cannot be reached. In recent years, We learned that postmortem MRI (25,26) and micro CT (27,28)or as an alternative to the autopsy confirm the fetal diagnosis post-mortem and obtain more detail benefits. It is undeniable that this is much more advanced than the cast mold to some extent (Fig. 4-5). However, our team (especially Cardiologist and junior residents) believes that the casting technology still has advantages. After all, the MRI and micro CT images are too professional and not easy to understand. The casting model can directly show the detailed path of large blood vessels and their branches, which is more convenient for medical teaching. A complex CHD deformity model can bring a deep visual impression to medical students. Moreover, we can also carry out the casting process after postmortem MRI or micro CT.
With the continuous development of prenatal diagnosis techniques, the opening of “the second child policy”, and the increase in the pregnant women with advanced maternal age, the medical disputes of prenatal diagnosis in China are increasing by 15-20% every year, and the medical disputes due to the diagnostic defects lead to the deterioration of the doctor-patient relationship. In addition, based on China’s special social medical insurance model, if pregnant women do not buy expensive congenital disability insurance before neonatal delivery, once newborns are diagnosed with congenital malformations, huge treatment costs are needed to be borne by the families. They have to claim huge compensation from the hospital, which is very different from the advanced medical insurance system in Europe and America. Therefore, many families have to abandon these children with congenital diseases after childbirth (Fig. 3). Some children were subsequently adopted by foreigners,the same situation also prevails in India and other extensive Southeast Asian regions. Thus, the accuracy of prenatal diagnosis is very important in China, which can not only provide anatomical details for the postpartum surgery, but also reduce the burden on the families and society, and reduce unnecessary medical disputes. Of course, it is more important to deepen the reformation of the domestic medical system by learning the advanced medical insurance system in Europe and America (8,21).
The casting of fetal cardiovascular model is indeed a novel and futuristic technology, but it is difficult to perfect the casting model and widely used in clinical practice. In addition, it must be considered that above all the pathologies of the arch and the obstructive ones are also evolutionary so it is not excluded that the ultrasound diagnoses may be late. Prenatal ultrasound has well-known limitations so it seems exaggerated to pretend that diagnoses can be made as the isolation of the epiaortic trunks. They are, in fact, diagnoses that are notoriously performed after birth. In fact, the best weeks at which heart disease can be seen by ultrasound are between the 18th and 22nd internationally; but it is limited to China's prenatal diagnosis regulations and special medical insurance system. Pregnant women usually carry out fetal malformation screening at 24-28 weeks or above, so I'm sorry that my medical institution can only carry out screening at 24-28 weeks, the diagnosis would not be so timely for intrauterine treatment. The method can be used to confirm prenatal diagnosis or to diagnose missed cases in poly-malformed cases undergoing TOP for other reasons, but cannot be done as a gold standard in livebirths, obviously. This is the major limitation to be presented.