Management of complex CHD requires a thorough understanding of cardiac anatomy in order to define the better and appropriate surgical strategy. Although in simple forms of heart defects, traditional two-dimensional echocardiography remains sufficient to plan surgery; however complex forms often involve several abnormalities of the heart and great arteries that make the interpretation of spatial relationships from sequential two-dimensional cuts very difficult. Recently the creation of a real physical model of the heart and great arteries became possible because of the rapid prototyping technique and the advent of high-performance three-dimensional printers.Reference Costello, Olivieri and Krieger 1 In this case report, we used the new technology of three-dimensional printing to create a physical model of a neonatal heart with a complex CHD, which was helpful for surgical repair.
Case report
A newborn presented after birth with refractory cyanosis and a systolic heart murmur; two-dimensional echocardiography revealed a complex cyanotic CHD. The pulmonary artery arose entirely from the left ventricle, with a fibrous continuity between the pulmonary valve, which was severely stenotic, and the anterior leaflet of the mitral valve. The aorta overrode the interventricular septum, with a subaortic ventricular septal defect.
Imaging method and segmentation
Multi-detector-row CT was performed using 64-slice Somatom Definition CT scanner (Siemens, Forchheim, Germany). CT was obtained, using the following protocol: echocardiography gated, rotation time 330 ms, slice thicknesses 0.6 mm, and tube current and voltage 36 mAs and 80 kVp, respectively. Cardiac CT confirmed the anatomical relationships described above by echocardiography (Fig 1). CT Digital Imaging and Communications in Medicine data sets were then imported into dedicated post-processing software (Mimics® Innovation Suite, Materialise NV, Leuven, Belgium), and heart segmentation was then performed. The apical part of the model was sliced so that the inside of the model could be easily visualised for surgical planning; 3-matic software® (Materialise, Leuven, Belgium) was used afterwards to process the digital model, and finally printed using a three-dimensional printer with HeartPrint® flex material (Materialise).
Cardiac CT demonstrating the pulmonary artery (PA) arising entirely from left ventricle (LV). The aorta which overrides the inter-ventricular septal defect (arrows) is anterior and to the left of the pulmonary artery. AV=aortic valve; RV=right ventricle.
Three-dimensional model analysis
The physical model of the neonatal heart offered a better understanding of spatial relationships between great arteries and other intra-cardiac structures. The team involved in the patient’s care was able to discuss the therapeutic strategy around a table while holding the heart in their hands. The size of ventricular septal defect and its position closely related to the aorta showed the possibility to create a baffle from the left ventricle to the aortic valve through the large ventricular septal defect, without the risk of sub-aortic stenosis (Fig 2a and b). The aortic valve was anterior and to the left of the pulmonary valve, and pulmonary artery bifurcation was located to the right side of the aorta, and thus it was considered that it will be easier to implant the right ventricle-to-pulmonary artery conduit to the right side of the aorta. Surgical repair was carried out at the age of 5 months. Perioperative surgical observation of the heart revealed exactly the same anatomy of the printing model with regard to size, position of ventricular septal defect, and its relationships with the great arteries. A Dacron patch was used to create a baffle connecting the left ventricle to the aorta through the ventricular septal defect, and a right ventricular conduit was implanted to the right of the aorta as expected. The baby did well 6 month after his cardiac surgery.
The digital three-dimensional model of the neonatal heart before printing seen from left ventricle (LV) ( a ). Printed three-dimensional model ( b ). Arrows indicate the ventricular septal defect. Ao=aorta; AV=aortic valve; MV=mitral valve; PV=pulmonary valve; TV=tricuspid valve.
Discussion
Even though three-dimensional printers were first developed in the 1980s, their use in clinical practice was not adopted because of low-resolution images and lack of computer processing power. The rapid technological progress during the last few years has allowed the development of more performant three-dimensional printers with high-resolution images. At present, three-dimensional printing of CHDs has emerged as an established tool to assist diagnostics, for educational purposes, and intervention planning.Reference Costello, Olivieri and Krieger 1 – Reference Olivieri, Krieger, Chen, Kim and Kanter 3 Typically, the source images for these models are derived from a high-resolution cardiac imaging such as MRI or CT scan. Recently, three-dimensional models derived from three-dimensional echocardiographic data sets are technically feasible for small zone of interest such as ventricular or atrial septal defect.Reference Olivieri, Krieger and Loke 4 , Reference Samuel, Pinto, Pietila and Vettukattil 5 Although echocardiographic data actually do not allow to print the whole heart with the great arteries because of a lower spatial resolution of three-dimensional images with larger volume data set; however this could be achieved in the near future with the development of a more powerful matrix probes.
In our case, the baby had a complex CHD consisting of a double-outlet left ventricle. This rare malformation is defined by both great arteries emerging completely – complete form – or mostly – incomplete form – from the morphological left ventricle. The inter-relationships of the great arteries, the position of ventricular septal defect, and its spatial relationships with the great arteries are widely variable.Reference Van Praagh, Weinberg and Srebro 6 Understanding of these arrangements are crucial to define the best surgical strategy, which also varies according to the anatomy.Reference Bharati, Lev, Stewart, McAllister and Kirklin 7 In most of these cases, we need another imaging modality to better understand the complex anatomy, such as MRI or CT scan, in addition to echocardiography. Despite these additional imaging studies, this complex arrangement of structures cannot be viewed simultaneously. The result of these images is a two-dimensional representation of a three-dimensional complex anatomy. two-dimensional images lack the ability to display the entire arrangement of the different structures in a single plane, and the operator has to rely on his interpretative mental skill to compile the two-dimensional slices in a three-dimensional anatomy. The use of three-dimensional printing model removes the potential for misinterpretation that may occur between the presentation of images in two dimensions and the mental reconstruction and provides a better definition of intra-cardiac spatial relationship. This new innovative technology allows better understanding of the anatomy of complex CHDs, and the insight provided by this technology may help increase procedural efficiency, and improve surgical outcomes in such patients.
Acknowledgements
None.
Financial Support
This research received no specific grant from any funding agency or from commercial or not-for-profit sectors.
Conflicts of Interest
None.
Ethical Standards
The authors assert that all procedures reported comply with the ethical standards of the Helsinki convention, and consent for publication was obtained from the patient’s family.
