**3. Models for decision support: a case study**

By establishing a conversation with clinicians and embedding the technology within the hospital, it is possible that complicated cases requiring additional insight are brought to the attention of the engineer for the creation of a model, which could be either a computer simulation or a 3D-printed model, or both. The model is created specifically to appreciate features that have clinical implications. An interesting example is represented by a patient (19 year-old male) who presented a diagnosis of aortic coarctation, previously stented, and also had an aberrant left subclavian artery originating from the stent site. The discussion revolved around the possibility of inserting a Cheatham Platinum (CP) covered stent within the existing device to prevent formation of a small developing aortic aneurysm, without occluding the aberrant subclavian artery. Insight into the relative position of all these components was therefore desirable, and a model was reconstructed from CT data, including the stent. The aorta was printed in transparent rigid resin, while the stent was printed using a white stereolithography (SLA), therefore being easily identifiable within the anatomy. Furthermore, a cut was performed alongside the thoracic/descending aorta such that the model could be easily opened and, if necessary, to gather additional measurements. The model (**Figure 4**) contributed to assess the feasibility of the intervention highlighting the spatial relationship between stent, aneurysm and left subclavian artery. Additional computational analyses (including the same 3D domain) were performed to simulate the implantation of the CPcovered stent and the local fluid dynamics post implantation [16]. The intervention was performed successfully.

novel device was developed. The latter was designed with the intention of fitting more dilated RVOTs. In this case, a patient-specific 3D model resulted extremely valuable for practicing device insertion prior to performing the first implantation of the novel device on compassion‐ ate grounds (i.e. first-in-man procedure). A candidate (42-year-old male) presented with a history of cardiac surgeries, deemed not suitable for additional surgery, and, however, still presenting with severe pulmonary regurgitation. The morphology and dimensions of his RVOT suggested that the second-generation PPVI device would have been suitable. A model was created from his computed tomography (CT) examination and 3D printing. As shown in **Figure 3**, the cardiologist was then able to use the model to practice device insertion and deployment prior to the procedure. Particularly, having access to the model allowed the cardiologist a) to guide device personalisation to assure safe anchoring in the specific anatomy and b) to identify a problem in deploying the device if accessing via the right pulmonary artery —conventional approach—while he could successfully deploy it when inserting the line via the left pulmonary artery. The latter strategy was used (successfully) on the day of the

**Figure 3.** A 3D-printed model was used for testing insertion and deployment of a novel device (second-generation, self-expandable PPVI stent). As a valuable practice tool, testing the procedure in the model is allowed to identify an unfeasible access route. LPA, left pulmonary artery; RPA, right pulmonary artery. . Stent diameter at extremities = 40.7

By establishing a conversation with clinicians and embedding the technology within the hospital, it is possible that complicated cases requiring additional insight are brought to the attention of the engineer for the creation of a model, which could be either a computer simulation or a 3D-printed model, or both. The model is created specifically to appreciate

**3. Models for decision support: a case study**

procedure [15].

126 New Trends in 3D Printing

mm.

**Figure 4.** Patient-specific 3D model of stented coarctation, printed with two different materials to better highlight the position of the device (length = 28 mm), including the possibility of opening the model to better appreciate the relative position of the stent with respect to the rest of the anatomy.
