Development of a patient-specific epicardial guide for ventricular tachycardia ablation surgery using high-consistency rubber silicone molding

BACKGROUND: Concomitant epicardial ablation of ventricular tachycardia (VT) remains a clinical challenge in cardiac surgery due to the need for intra-operative mapping. A preoperative patient-tailored epicardial guide could provide an intraoperative 'blueprint' of arrhythmogenic target substrate, thereby facilitating the workflow. Thus far, no 3D printing material or technique has fully met the requirements for this application. This study explores the feasibility of high-consistency rubber (HCR) silicone molding to produce low-cost, customized guides for VT scar ablation. METHODS: An inverted mold was created in Meshmixer using merged LGE-CMR and cardiac CT images of a 61-year-old VT patient, and printed using fused deposition modeling. HCR silicone was milled, sculpted, and trimmed to fit the negative mold. The guide was cured, subjected to autoclaving, and bench-tested on an ex vivo porcine heart model using radiofrequency and cryo-ablation. Various durometers and thicknesses were tested to determine the optimal fit for our application. RESULTS: MED-4072 and MED-4080 silicone (thickness range: 2.0-3.4 mm). Models with 2.1-3.0 mm thickness and 70 Shore A hardness achieved the best balance between flexibility and rigidity for application on a beating heart. The thinnest model (2.0 mm) was too pliable for stable placement. The guides withstood autoclaving and ablation procedures (radiofrequency; cryo-energy) without deformation or compromising structural integrity. CONCLUSIONS: The HCR silicone molding technique allows for the production of flexible, cost-effective epicardial guides for VT ablation, minimizing the need for a full electrophysiology team throughout the entire procedure.