## 1 Introduction
To our knowledge at the time of this study, the Heartroid EP Model (Heartroid, Kyoto, Japan) (Figure 1A,B) is the best commercial off-the-shelf physical simulator for radiofrequency CA (RCA), thanks to its many unique features and its compatibility with any EAM system. The system consists of a hemodynamic pump, a full transparent conductive heart phantom, a 6-L tank of saline, and a foam block with a valve recreating the leg. The heart phantom's atria are interconnected via a set of three holes placed on the atrial septum; the four chambers interconnect with coronary vessels and valves. Tools are entered through an adjustable valve that simulates catheter entry through the leg foam block. Compatible with EAM, including the CARTO mapping system (Biosenese Webster, Irvine, CA, USA), one of the leading EAM systems, this simulator is able to recreate mapping, tracking, and ablation in all four chambers of the heart. CARTO patches and cables can be connected from the outside of the simulator tank via a series of stainless steel bolts and washers (Figure 1A,B). Unlike virtual simulators, physical simulators make use of real catheters in a real catheterization laboratory, exposing the trainee to a more realistic experience without endangering patients. This physical system costs approximately GBP 10,000-15,000 [12]. Due to the high costs associated with commercial simulators for electrophysiology, multiple institutions have made use of 3D printing technology to develop their own electrophysiology simulators compatible with EAMs [13; 14; 15; 16]. [PERSON] et al. [15] present an experimental simulator consisting of a selective laser sintering (SLS) 3D-printed full heart model, made with thermochromic polyurethane and placed in a saline tank (Figure 1E). This system achieved realistic tactile feel during catheter manipulation and realistic body-like temperatures by pumping the system with thermostat-regulated 37 \({}^{\circ}\)C saline [15]. Similarly to Heartroid, the patches were in contact with the catheter tip via saline; however, the tank in this model was shaped as a torso to enhance realism. The system was paired with the CARTO mapping system and an electrocardiogram signal generator to recreate the electrophysiological conditions of the body. The total cost of construction was approximately GBP 6000 and 150 h of labor [15]. Similarly, our previous research [13] presented methods to build a low-cost, easy-to-replicate experimental simulator for CA, making use of fused deposition modelling (FDM) 3D printing. The simulator (Figure 1C,D) was composed of a saline tank containing a thermochromic biatrial phantom, a base to hold the phantom, and six probing tubes that hold the CARTO patches in the saline. The heart phantom presented in the article only contained two atria, focusing on atrial ablation training. To connect the chambers, a transeptal hole was placed in the fossa ovals to enable access into the left atrium. The phantom was FDM 3D printed in Layfomm40 (CC-Products, Koln, Germany): a mixture of thermoplastic polyurethane and polyvinyl alcohol. The printed phantom was coated in paint to render its surface radiopaque and thermochromic. The phantom was soaked in 0.9% saline, and then placed in the simulator for ablation. Ten thermochromic ablation lesions were successfully performed on the posterior wall of the right atrium, providing an effective proof of concept for this manufacturing methodology. Though not as intricate as the experimental system proposed by [PERSON] et al. [15], this system is arguably more accessible to a wider academic audience by proposing low-cost materials and common 3D printing solutions. The experimental simulators presented by [PERSON] et al. [13] and [PERSON] et al. [15] were proven to be effective in simulating the procedure; however, comparisons against  
Figure 1: **(A)** The Heartroid EP Model training system. The translucent conductive heart phantom (1) is placed inside of a 6l saline tank (2) and connected to a pulsatile pump.