Abstract Introduction Interventional cardiology training has a long learning curve and exposes patients and clinicians to undesirable procedural risks. We aim to assess whether mentored simulation-based training with three dimensional (3D) printed models can improve the procedural skills and safety performance of beginners in coronary diagnostic procedures. Methods Twenty-nine final-year medical students from a single centre were lectured in the basic principles of invasive coronary angiography (ICA) for one-hour, and then randomized to conventional training or simulation training. Conventional training (n=15) consisted in watching a 20-minute video demonstrating all ICA steps in a 3D-printed coronary simulator. Simulation training (n=14) offered the same explanations in a hands-on training session with the 3D-printed model, in pairs, for 20 minutes. The co-primary endpoint was efficacy and safety of performing a simulated ICA in the 3D-printed simulator, installed under sterile drapes, in a conventional angiography suite. Efficacy and safety were graded by a blinded investigator using a pre-specified performance checklist, including the identification of procedural "red flags", graded 0-100%. The secondary endpoint was theoretical knowledge, assessed in a 25-question multiple-choice quiz, graded 0-100%. Results All participants completed the training and evaluation phases. Both elements of the co-primary endpoint were superior in the simulation group: efficacy score of 91.5 ± 3.8 vs 64.6 ± 8.3% and safety score 100.0 (100.0-100.0) vs 62.5 (20.8-79.2) %, p<0.001. The median number of "red flags" were 2 (1-4) in conventional and 0 (0-0) in simulation training recipients (p<0.001). Secondary endpoint was higher in simulation training: 85.7 ± 9.0 vs 76.8 ± 12.7% (p=0.039). Conclusion Mentored simulation-based training of medical students in ICA with 3D-printed models resulted in improved performance regarding efficacy, procedural safety, and theoretical knowledge.ResultsSimulation and evaluation setup