**2. Early experience: testing a novel cardiovascular device**

One important application of 3D printing in CHD is represented by aiding in patient selection for specific procedures. In this context, the usefulness of 3D-printed models was assessed specifically for evaluating shapes and sizes of the right ventricular outflow tracts (RVOTs) in patients that would be possible candidates for percutaneous pulmonary valve implantation (PPVI). As a Centre leading in the introduction of PPVI in clinic [12] as well as its evaluation with engineering analyses [13], 3D printing patient-specific models represented an additional valuable tool for determining PPVI suitability. A study [14] demonstrated that having access to 3D models in addition to cardiovascular magnetic resonance (CMR) imaging data resulted in cardiologists improving the indication of patients suitable for implanting the first PPVI device (Melody® valve, Medtronic Inc) (**Figure 2**).

**Figure 2.** Example of 3D-printed RVOTs from 12 patients [ref].

Within the context of PPVI and in relation to early observation on the first generation device being suitable for only a small portion of patients requiring pulmonary valve replacement, a 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 procedure [15].

**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 mm.
