A waiver from the local medical ethical committee was obtained.

Thirteen patients are enrolled in this study, who had their definite procedure from 2011 to 2023.

The non-consecutively included cDORV patients with 3D prints had a median age of 13.5 months (IQR = 3.0–48 months) during the definite procedure. As shown in Table 1, 9 patients are diagnosed with TGA; 3 patients had normal relationship of the arteries (NRA); and in one patient the aorta was left to the pulmonary artery. As seen in Table 5 in Appendix 1, 11 patients underwent palliative surgeries before the definite biventricular or univentricular procedure: six patients received a Pulmonary Artery Banding (PAB), 3 patients received Bidirectional Cavopulmonary Anastomosis (BCPA), and 4 patients received one or more Modified Black Taussig Shunts (MBTS).

All CT scans were performed on a 320-detector row CT scanner (Toshiba AquilionOne, Otawara, Japan) using the pediatric setting which is according to body weight [6]. All CT scans (n = 13) had adequate image quality and allowed for image segmentation for the 3D print. Echo, angiography, and CT scans were used to compare the feasibility of predicting surgical technique to 3D prints.

We have designed and printed heart models since 2011. Our protocol for design and fabrication of a patient-specific 3D-printed heart model has been previously described in the literature [13,14,15,16,17].

Image segmentation was based on the previously acquired CT scans using ITK snap [18]. User-guided 3D active contour segmentation of anatomic structures significantly improved efficiency and reliability. Neuroimage 2006; 31:1116–28.] software was used by a consultant CHD cardiologist with more than 10 years expertise in cardiac imaging. The segmented geometry was exported as a 3D surface file into Meshmixer version 11.0.544 (Autodesk Inc., San Rafael, CA, USA) for computer-aided design. A 0.8-mm outer shell was added outside of the cardiovascular structures interface. The geometry was processed by Cura version 15.02 (Ultimaker BV, Netherlands) and sent to the 3D printer (BQ Witbox, Spain). All models were fabricated in polyurethane filament by fused deposition modeling. All heart models were able to be cut open and evaluated and most were printed as soft plastic, and some were made from harder plastic but no difference in quality of evaluation was seen depending on the material.

All diagnostic imaging were evaluated retrospectively by both a pediatric cardiac surgeon and a pediatric cardiologist. In Table 1, we evaluated all the different diagnostic aspects and anatomic features of the included patients (n = 13) (see Appendix 2). Figure 1 and Fig. 2 shows examples of 3D prints used to assess surgical procedure. In Fig. 3, an echo image is seen from a patient where there was no clear visible VSD while the LV is visible. This was however seen with a 3D model which demonstrated that this DORV could be septated to a biventricular heart after arterial switch and VSD closure.

Three-dimensional prints used for determining surgical approach and technique. Own photographs that have not been previously published. Picture on the right shows LV to AO patch

Three-dimensional prints used for determining surgical approach and technique. Own photographs that have not been previously published. Picture on the right shows biventricular repair at age of 6 weeks, LV to PA tunnel (via RV-tomy)

Echocardiographic long-axis view with no VSD visible

All relevant data are within the manuscript and its Supporting Information files.

Table 1 and 5 in Appendix showing patient characteristics and previous palliative surgeries.

Patient characteristics obtained from 3D print important for surgical planning.