# Cardiac Radiofrequency Ablation Simulation Using a 3D-Printed Bi-Atrial Thermochromic Model
## 1 Introduction  
Cardiac ablation therapy is a minimally invasive interventional procedure used in the treatment of cardiac arrhythmias. The process involves the insertion of flexible catheters through peripheral blood vessels, which are guided to the site of abnormal electrical conduction in the myocardium. Here, the arrhythmia is terminated via destruction of the pathological tissue, most commonly using radiofrequency ablation (RFA). The procedure is performed in the cardiac catheterization laboratory under X-ray fluoroscopy guidance andoften with the use of an electroanatomic mapping system (EAMS), which tracks the inserted catheters and allows measurement of the patient's cardiac anatomy and electrophysiology. [PERSON] et al. describe the current strategies and technologies for the ablation of the most common arrhythmia, atrial fibrillation [1]. RFA procedures are complex and require considerable training, sometimes delivered via computer or physical simulators. Computers and physical simulators have an ethical and cost advantage but may lack fidelity. An example of a computer simulator is the Mentice VIST (Mentice AB, Goteborg, Sweden), which has been shown to improve electrophysiology-trainee performance [2]. The requirements for a high-fidelity physical simulator for cardiac RFA make it challenging to produce such a simulator. These requirements include representation of the cardiac anatomy, soft material properties, realistic appearance under imaging (particularly X-ray fluoroscopy), compatibility with EAMSs, sensitivity to RFA, and generation of electrophysiological signals. We are not aware of any physical simulator that meets all these criteria. However, several simulators have been developed that meet a subset of the criteria. [PERSON] et al. [3] developed a physical simulator using a 3D-printed whole heart model embedded into a custom torso. The heart was printed using thermoplastic polyurethane and the simulator was compatible with the CARTO's EAMS (Biosense Webster, Irvine, CA, USA). The simulator was evaluated by 10 electrophysiologists and used to compare novel to experienced operators. Similar simulators are produced by Heartroid (JMC Corporation, Yokohama, Japan, [[https://www.heartroid.com/itemlist/ablation/](https://www.heartroid.com/itemlist/ablation/)]([https://www.heartroid.com/itemlist/ablation/](https://www.heartroid.com/itemlist/ablation/)), accessed on 1 December 2021) and Pangolin (Tel-Aviv, Israel, [[http://pangolin.co.il/en/gallery/simulators-endo-vascular/](http://pangolin.co.il/en/gallery/simulators-endo-vascular/)]([http://pangolin.co.il/en/gallery/simulators-endo-vascular/](http://pangolin.co.il/en/gallery/simulators-endo-vascular/)), accessed on 1 December 2021). However, none of these physical simulators have sensitivity to RFA, meaning that ablation lesions cannot be created in these simulators and as a result, effects of intended therapies delivered by trainees cannot be quantified. Lesion formation depends on the parameters of the RFA, such as power, duration, ablation temperature and importantly, the contact force between the ablation catheter and the tissue [4]. Therefore, a simulator that allows creation of lesions will add a valuable layer to assessing a trainee's progression. Several attempts have been made to create a physical simulation medium that is sensitive to RFA and therefore able to demonstrate lesions. [PERSON] et al. [5] used a polyacrylamide gel with bovine albumin which produced a noticeable color change after RFA due to coagulation between 50 and 60 \({}^{\circ}\)C. [PERSON] et al. [6] proposed the use of thermochromic pigments to create RFA-sensitive models that produced a permanent color change above 60 \({}^{\circ}\)C. However, there have been no attempts to incorporate ablation-sensitivity into a cardiac RFA simulator. 3D-printed models are widely used in the medical field for a variety of purposes.