Design of an Esophageal Deflection and Thermal Monitoring Device for use during Cardiac Ablation Procedures
Cardiac ablation is a common procedure performed by cardiac electrophysiologists. The clinician will use a device, such as a radiofrequency ablation catheter, to thermally ablate or burn off defective heart tissue (myocardium). During the procedure, the esophagus can be in close proximity to the heart tissue. As heat transfers through the myocardium, it can also transfer to the esophagus, potentially damaging the esophagus tissue. The damage results in thermal lesions and, in worst-case scenarios, atrioesophageal fistulae. The work reported in this thesis was performed to devise a tool and method to protect the esophagus during the ablation procedure. The Esophageal Deflection Device (EDD) was designed and manufactured to move the esophagus away from the ablation location. The device comprises of a straight rod and a precurved overtube. If the rod is inserted into the overtube, the overtube is straightened out by the rod. If the assembled device is inserted into the esophagus, and the rod is retracted, the elastic memory effect will cause the tube to reassume its original curved shape, thereby moving the esophagus safely away from its close position to the heart. In this dissertation, the medical problem along with the design tools needed to address the above problem of moving the esophagus are investigated. The materials used for the Esophageal Deflection Device are reviewed, and the testing of 3D printed hyperelastic photopolymers used during preliminary designs is performed. Theoretical, experimental, and numerical methods were used to characterize the bending behavior of the Esophageal Deflection Device, and the Mooney-Rivlin materials properties for the hyperelastic tube material are determined. Thereafter, a temperature sensing Esophageal Deflection Device is described and tested. The temperature distribution during ablation is simulated using finite element analysis. Experimental and numerical results are discussed and compared. Finally, a summary and future direction of this work and our research is provided.