Printed 3D models have demonstrated their usefulness in revealing the target anatomy before intervention in a wide range of congenital heart conditions. This gives specialists a level of confidence not achieved with virtual 3D imaging techniques. For example, the use of printed 3D models in presurgery planning can improve postsurgery blood flow after complex surgical repairs such as the Nikaidoh procedure in patients with transposition of the great arteries associated with interventricular communication and outflow tract obstruction.12

Printed 3D models have also been used to demonstrate suitability for biventricular repair among patients who would otherwise have been palliated to univentricular repair, as demonstrated by Farooqi et al. in a patient with a double outlet right ventricle and a remote ventricular septal defect.9

Another highly attractive application of 3D models is in planning interventions to treat left heart hypoplasia, including the Glenn, Norwood, and Fontan procedures.2,8,33 For example, Kiraly et al. used a 3D model to plan the Glenn procedure in a 5-year-old boy with left heart hypoplasia and aortic obstruction at several locations (Figure 4).2 Finally, 3D models can also be a useful pretransplant planning aid for intervention in patients with a failing Fontan circulation, in whom the distortions produced by previous surgery can necessitate technical approaches different from those used in conventional patients.34

Figure 4.

A: Glenn procedure simulation with a 3-dimensional (3D) model simulating the surgeon's intraoperative view. The discontinuous black lines mark the desired incision. The 3D model was opened and the stenotic segments resected (discontinuous red lines). The autologous tissue leaflets were folded to enlarge the aortic arch (red arrows). B: Intraoperative view during surgery. The incision was made from the neoaorta to the junction with the transverse arch and was then extended toward the common brachiocephalic trunk and the descending aorta. The stenotic posterior membrane was resected (discontinuous red line). The cardioplegic solution was injected into the native aortic root through a 6 Fr-Foley catheter. C: Intraoperative view after completion of the autologous patch enlargement. AoAs, native ascending aorta; AoD, descending aorta; BCT, brachiocephalic trunk; LCA, left carotid artery; LSA, left subclavian artery; LSVC, left superior vena cava; Neo-Ao, neoaorta (native pulmonary trunk); PT, pulmonary trunk; RV, right ventricle; VC, venous cannula. Adapted with permission from Kiraly et al.2

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Printed 3D models are thus finding applications in the evaluation of internal cardiac features such as defects in the atria13,21 and ventricles20,33,35; however, their use is not limited to the heart, and they have also been used to evaluate vascular anatomy, for example aortopulmonary collaterals in patients with pulmonary atresia and ventricular septal defects. Printed 3D models provide highly detailed information about the position and intricate path of the collaterals, which is extremely useful in presurgery planning (Figure 5A).4,8

Figure 5.

A: Actual-size 3-dimensional (3D) model of the heart and great vessels of a 1-day-old male patient with pulmonary atresia, confluent pulmonary branches connected to the pulmonary artery, and multiple aortopulmonary collateral arteries (MAPCA). Reproduced with permission from Ryan et al.4 B: 3D model of a cardiac tumor (1, green) located in the free wall of the right ventricle (2, red). Reproduced with permission from Schmauss et al.35

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For patients with cardiac tumors or hypertrophic cardiomyopathy, the key factor in selecting the surgical strategy is lesion size, which determines the choice between partial or total resection and heart transplant. In these patients, 3D printing with different materials and colors is especially useful because it can reveal lesion position, the tumor vasculature, and the spatial relationship between the lesion and the valves, subvalvular apparatus, and papillary muscles. This application has already been used to plan the total resection of an right ventricular (RV) fibroma35 and septal myectomy in a patient with hypertrophic cardiomyopathy.5

Due to the varied range of aneurysms, aortic dissections, and surgical histories, surgery of the aortic arch remains highly challenging. Through the use of 3D models, aortic diameters and anatomy can be reproduced accurately, allowing preoperative planning and in vitro simulation. The precision afforded by 3D modeling is essential for selecting an appropriate endoprosthesis, as described by Schmauss et al. for a patient with an extensively atherosclerotic aortic aneurysm considered for the frozen elephant trunk procedure.36 The same group also used 3D models to plan aortic valve replacement surgery in a patient with a history of surgical coronary revascularization.37 Another potential application of 3D models is in the design and testing of personalized external aortic root support implants for Marfan syndrome patients; these implants are an innovative alternative for stabilizing the distended aortic root and minimizing dissection risk.38

The risk of an atrial septal defect closure device becoming dislodged after implantation is usually determined by the size of the defect and above all by the catheterization specialist's experience and skill in judging whether the defect rims are large and strong enough to support the device.40 It is sometimes difficult to determine if the risk of device embolization exceeds the risk of surgery; in this situation, 3D models can be a useful decision-making tool. This potential was highlighted in 2008 by Kim et al., who produced the first prototype printed 3D models to illustrate the broad spectrum of atrial septal defect morphology and size.41 The next step toward in vitro simulation came some years later in a study by Chaow et al., who demonstrated the utility of printed 3D models in selecting the appropriate device size for defects with an inadequate posteroinferior rim. Printed 3D models can also be useful when doubts remain about appropriate device localization after release, helping to exclude residual compression in neighboring structures (Figure 6, left).42

Figure 6.

Left. Testing the percutaneous closure of a 16 mm ostium secundum interatrial communication with a 17 mm Amplatzer Septal Occluder (blue). A and B: Segmentation from computed tomography images. C-F: Assorted views of the 3-dimensional model to check for appropriate device positioning and compression of neigboring vessels. Reproduced with permission from Bartel et al.42 Right. Simulated closure of a postinfarction ventricular septal defect with a 20 mm Amplatzer Septal Occluder (arrow), viewed from the right atrium. Reproduced with permission from Lazkani et al.43 Ao, Aorta; IVC, inferior vena cava; LA, left atrium; LSPV, left superior pulmonary vein; LV, left ventricle; PA, pulmonary artery; RA, right atrium; RSPV, right superior pulmonary vein; RVOT, right ventricular outflow tract; SVC, superior vena cava.

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Printed 3D models have also assisted decision-making in relation to ventricular septal defects. For example, Lazkani et al. used in vitro simulation with 3D models to select the appropriate device type and size for a patient with a postinfarction ventricular septal defect, achieving a positive outcome with no residual shunt (Figure 6, right).43

The variability and complexity of the mitral valve makes percutaneous treatment of mitral defects particularly challenging. In a previous article in Revista Española de Cardiología, Vaquerizo et al. described how 3D models can improve knowledge of local anatomy and potential interactions with transcatheter mitral valve replacement devices.44 The authors also highlighted the industrial potential of 3D mitral-valve modeling in the development and testing of new devices for a wide range of morphologies.

Another article described the use of a 3D model to plan percutaneous mitral annuloplasty.45 Simulation with the 3D model helped cardiac catheterization specialists to trial the complex navigational manouvers needed to advance catheters from the aorta to the left ventricle and position the catheter tip between the 2 papillary muscles and close to the mitral annulus. The 3D model was used to preprocedurally select the size of the deflectable guiding catheter and to optimize catheter positioning relative to the mitral annulus, resulting in a reported successful and safer outcome.

Most patients treated by transannular patch repair for tetralogy of Fallot are not indicated for transcatheter pulmonary valve replacement because of their large and irregular RV outflow tracts. In a landmark study, Phillips et al. used CT images to generate 3D models for 8 consecutive Fallot patients with a dilated RV outflow tract.46 The 3D models were used to develop individualized procedures to create a stable landing zone in a hybrid approach combining RV outflow tract remodeling with transcather pulmonary valve replacement. When the minimum right outflow tract diameter was > 26 mm, 1 or more covered stents were simultaneously implanted adjacent to a bare landing-zone stent onto which the pulmonary valve was then released. Finally, the lumen of the adjacent covered stent(s) was occluded with an Amplatzer Vascular Plug II (St. Jude Medical). In the authors’ estimation, the 3D models helped the whole multidisciplinary team to visualize the intervention, try out different strategies, and design individualized solutions for a population with widely differing cardiac anatomies. A similar approach has been used to treat transposition of the great arteries in a 15-year-old patient who had developed combined neo-pulmonary stenosis and regurgitation after arterial switch operation as a neonate (Figure 7).47

Figure 7.

Virtual reconstructions (A and B) and 3-dimensional models (C and D) from a 15-year-old male patient with great artery transposition and supravalvular pulmonary stenosis. Reconstructions and models were created after previous arterial switch surgery (A and C) and after implantation of a Medtronic Melody valve (B and D). Reproduced with permission from Poterucha et al.47

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Endovascular stenting is an alternative to surgery in patients with aortic arch hypoplasia associated with aortic coarctation; however, an overlong stent can block the supra-aortic trunks, whereas a small stent can migrate from the implantation site.48 Our group used a 3D model derived from MRI scans to simulate intervention in a 15-year-old male patient with transverse aortic arch hypoplasia10 (Figure 8). Because the model was radioopaque, fluoroscopy guidance could be used to visualize navigation with conventional catheters. This allowed unlimited simulation of different interventional strategies to determine the optimal stent length and release site. We were then able to faithfully reproduce the selected procedure in the patient, using the same technique, catheters, and devices, thereby minimizing intraprocedural improvisation and patient risk and achieving a positive outcome.

Figure 8.

Stent placement in a 15-year-old male patient with aortic arch hypoplasia. Comparison of preintervention simulation with a 3-dimensional printed model (A1-D1) and the real intervention in the patient (A2-D2). Reproduced with permission from Valverde et al.10

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Printed 3D models have also been used to support endovascular repair of aortic aneurysms. Sodian et al. used 3D models to design bespoke devices to seal perianastomotic drains after ascending aorta and transverse aortic arch replacement surgery.49 The authors found not only that simulations with the 3D model were useful in selecting the best strategy for pseudoaneurysm closure, but also that they helped to engineer an individualized device tailored to the patient's anatomy. In another article, the same research team used this technology to plan transcatheter aortic valve replacement in a patient with severe aortic stenosis and a porcelain aorta (Figure 9A).36

Figure 9.

A: 3-dimensional (3D) model after the frozen elephant trunk procedure to treat an extensively atherosclerotic aortic aneurysm. The image shows the prosthetic ascending aorta (+) and supraaortic trunks (*) and the aortic arch stenting (arrows). Reproduced with permission from Schmauss et al.36 B1: 3D model evaluating aortic root and coronary artery morphology. B2: Retrospective prediction of paravalvular aortic regurgitation (arrow) by shining light on a printed Edwards-SAPIEN valve positioned in the 3D model. B3: Transesophageal echocardiography in the patient showing residual aortic regurgitation (AR) after valve placement. Reproduced with permission from Ripley et al.50

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A more systematic examination of the use of 3D models to predict the outcome of transcatheter aortic valve replacement was presented by Ripley et al. (Figure 9B).50 The study examined a series of 16 patients, 9 with paravalvular aortic regurgitation on postprocedure echocardiography and 7 with no residual leakage. The authors created 3D models for these patients from preprocedure cardiac CT scans and used these models to retrospectively predict the shape and location of the periprosthetic leak. The 3D models accurately predicted dehiscence in 6 of the 9 patients with paravalvular aortic regurgitation (6 true positives and 3 false negatives) and excluded residual leakage in 5 of the 7 control patients (5 true negatives and 2 false positives). The authors recognized that major challenges remain, such as ensuring that models accurately reproduce the mechanical properties of tissues; however, they concluded that this technology is making giant steps toward clinical implementation in the not too distant future.

Pulmonary venous baffle obstruction is a well-known complication in patients with transposition of the great arteries corrected by the Senning technique. Catheter approaches are a viable alternative to surgery but require meticulous planning in order to avoid complications. Olivieri et al. created a 3D model to plan catheter access and evaluate the positioning of several stents in the stenotic baffle and their relationship to neighboring structures.7 The authors found that the in vitro simulation improved procedure efficiency in the patient and reduced radiation dose, procedure time, and potential complications.