**1. Introduction**

#### **1.1. 3D printing in medicine and congenital heart disease**

3D printing technology represents an extraordinary innovation, which has been compared to a 'second industrial revolution' [1]. In May 2015, an article in the Harvard Business Review commented that 'industrial 3-D printing is at a tipping point, about to go mainstream in a big way. Most executives and many engineers don't realise it, but this technology has moved well beyond prototyping, rapid tooling, trinkets, and toys' [2]. Indeed, applications of 3D print‐ ing technology now range from the automotive industry to archaeology, from eyewear and fashion design to medicine. It is the medical field that experts in the sector indicate as the area

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in which the technology will play a really substantial and potentially revolutionary role in the coming years [3]. But 3D printing has been used for medical purposes well before recent technological advances and the press hype that ensued, with highly sensational titles in the media along the lines of '3D printer saves baby's life' [4]. Examples of medically relevant 3D models date back to the 1990s. Areas of medicine in which 3D printing technology can play an important role include manufacturing maxillofacial implants [5], personalising orthopae‐ dic prostheses [6], creating patient-specific implants for craniofacial surgery [7], and even reconstruction of wound models for forensic purposes [8]. From renal [9] to cardiovascular [10], a range of models has now been manufactured and described, based on the underpin‐ ning principle that 3D printing technologies allow to print patient-specific models recon‐ structed from volumetric medical imaging data, based on a processing framework discussed in more detail elsewhere [11] and summarised in **Figure 1**.

**Figure 1.** Framework for 3D printing cardiovascular 3D models, starting from medical imaging acquisition (1), proc‐ essing the image dataset with appropriate software (2 and 3) and generating a 3D volume (4) in a format compatible with the 3D printer.

The principle of being able to reconstruct patient-specific anatomical models and manufacture them by means of 3D printing (additive manufacturing, in particular) is especially appealing in the field of congenital heart disease (CHD). Patients with CHD are in fact born with complex, often unique, vascular and/or intra-cardiac anatomical arrangements. Parts of these complex anatomies get further manipulated and modified following cardiac surgery, with vessels being transposed, baffles being created, narrowed (i.e. stenosed) vessels being enlarged and whole areas (e.g. right ventricular outflow tract) being augmented by patches. The same patient can also receive implantation of cardiac devices, such as stents, valves prosthesis or occluder devices, during catheterisation procedures. Overall, the resulting unique scenario certainly warrants a patient-specific approach, which can be beneficial for different purposes:


in which the technology will play a really substantial and potentially revolutionary role in the coming years [3]. But 3D printing has been used for medical purposes well before recent technological advances and the press hype that ensued, with highly sensational titles in the media along the lines of '3D printer saves baby's life' [4]. Examples of medically relevant 3D models date back to the 1990s. Areas of medicine in which 3D printing technology can play an important role include manufacturing maxillofacial implants [5], personalising orthopae‐ dic prostheses [6], creating patient-specific implants for craniofacial surgery [7], and even reconstruction of wound models for forensic purposes [8]. From renal [9] to cardiovascular [10], a range of models has now been manufactured and described, based on the underpin‐ ning principle that 3D printing technologies allow to print patient-specific models recon‐ structed from volumetric medical imaging data, based on a processing framework discussed

**Figure 1.** Framework for 3D printing cardiovascular 3D models, starting from medical imaging acquisition (1), proc‐ essing the image dataset with appropriate software (2 and 3) and generating a 3D volume (4) in a format compatible

The principle of being able to reconstruct patient-specific anatomical models and manufacture them by means of 3D printing (additive manufacturing, in particular) is especially appealing in the field of congenital heart disease (CHD). Patients with CHD are in fact born with complex, often unique, vascular and/or intra-cardiac anatomical arrangements. Parts of these complex anatomies get further manipulated and modified following cardiac surgery, with vessels being transposed, baffles being created, narrowed (i.e. stenosed) vessels being enlarged and whole areas (e.g. right ventricular outflow tract) being augmented by patches. The same patient can also receive implantation of cardiac devices, such as stents, valves prosthesis or occluder devices, during catheterisation procedures. Overall, the resulting unique scenario certainly

warrants a patient-specific approach, which can be beneficial for different purposes:

**•** Experimentation for better appreciation of the physiology and haemodynamics

**•** Appreciation of anatomy for patients selection or device selection

in more detail elsewhere [11] and summarised in **Figure 1**.

with the 3D printer.

124 New Trends in 3D Printing

Based on this rationale, the cardiac engineering team within the Centre for Cardiovascular Imaging at Great Ormond Street Hospital for Children (London, UK) has advocated a patientspecific approach for studying and potentially treating CHD for several years now. In this light, 3D printing technology has been used extensively and for different purposes, focusing on the potential translation of the technique in the clinical realm. This chapter briefly presents an overview of the Centre's experience with 3D printing CHD, in order to create a showcase of the potential of the technique in the field. It will therefore touch upon clinical case studies, engineering experiments, and patients & public involvement and engagement (PPI/E).
