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[1,8]
or Owlet, for post-processing to establish a print-compatible model . This process involves converting
the object into a meshed surface file, hollowing the model, smoothing surfaces, and trimming vessels
[5]
or chamber walls in order to visualize the area of interest . The 3D rendered object is converted into a
[8]
computer-aided design format that can be converted into a physical object using a 3D printer .
Once complete, the 3D rendering undergoes rapid prototyping on a 3D printer. Capabilities of 3D printers
[9]
vary based on build volume, layer resolution, materials, and colors available . The print technology utilized
should be chosen based on the specific goal of the heart model. In making this decision, the material
needed, level of detail, and turnaround time are all taken into consideration. Options for 3D printing
[1]
include fused deposition modeling (FDM), Colorjet, Polyjet printing, and selective laser sintering . In
FDM, a thermoplastic filament is extruded in a specified pattern that immediately hardens. This process
[8]
typically has a shorter turnaround time and comes at a significantly lower cost . Colorjet printing is
an additive manufacturing technology in which a core material is spread in thin layers and solidified
by extrusion of a color binder. This technology allows for recreation of highly complex geometries in
[10]
relatively short production times . Polyjet printing, in contrast, allows for higher resolution printing
of multiple materials in different colors, but it is much more costly and thus less often employed for
[7]
routine modeling . This technique enables the use of flexible, translucent materials, which are optimal for
rehearsing surgical procedures as they can be cut, retracted, and sutured in order to effectively simulate
[1]
procedures . Additionally, selective laser sintering utilizes a high-power laser to fuse metal or ceramic
powder, resulting in a highly accurate model. This method, however, is often cost prohibitive in comparison
[5]
to other techniques . For each technique, the print material is sequentially layered, and the final model is
encased in support material, which can be removed manually or by soaking in a solution .
[9]

CLINICAL APPLICATIONS
The use of 3D printed models has been described widely for numerous percutaneous interventions for
the treatment of CHD. One of the most well described interventions in which 3D models play a role is
transcatheter valve implantation. These procedures represent the fastest growing area of innovation in
[8]
the field of pediatric interventional cardiology, with numerous devices developed in the last decade .
Transcatheter valve replacements are beneficial because they enable proceduralists to correct valve
regurgitation or stenosis without the need for repeat surgical interventions over the course of the patient’s
life [2,11] . Among these procedures, pulmonary valve replacement in repaired cases of Tetralogy of Fallot and
[12]
aortic valve replacement for aortic stenosis or regurgitation are the most widely described. Poterucha et al.
described a case of repaired tetralogy of Fallot in which the native right ventricular outflow tract (RVOT)
was deemed to be unfavorable for percutaneous intervention. A 3D model of the RVOT [Figure 1] was
then developed using 3D rotational angiography, which helped the interventionalist identify a landing zone
for implantation of a Melody Valve (Medtronic, Fridley, Minnesota). A study by Shievano and colleagues
showed that the use of 3D printed models allowed for more accurate selection of candidates for successful
[13]
[14]
percutaneous pulmonary valve implantation (PPVI) than 3D MRI reconstructions alone . Qian et al.
demonstrated the use of 3D printed models of the left ventricular outflow tract (LVOT) and aortic root of
patients with aortic stenosis. The models approximated the precise anatomy and flexibility of the LVOT,
which had substantial tissue calcifications, and were used to test valve implantation prior to the procedure.
This permitted the proceduralists to assess the feasibility of the intervention and predict paravalvular
leak after transcatheter aortic valve replacement [9,14] . To test paravalvular leak, the models underwent
analysis of strain distribution using a maximum bulge index, which aided in prediction of the degree of
leakage following percutaneous valve implantation. This technique ultimately assisted in identifying ideal
[15]
[14]
candidates for percutaneous rather than surgical intervention . Along the same lines, Ripley et al.
studied the use of 3D models to replicate patient-specific aortic root anatomy prior to transcatheter aortic
valve replacement, and they found that the models provide insight into how the patient anatomy will
interact with implanted medical devices. This enables interventionalists to predict potential challenges in
device placement and complications during or following the procedure.