Design of an esophageal deflection device for use during atrial ablation procedures

To prevent thermal damage of the esophagus during cardiac ablation surgery, a new device, named the esophageal deflection device (EDD), has been designed. The device consists of a curved elastic tube that is straightened by an inner rod (insertion rod) prior to insertion in the esophagus. After insertion of the assembled device in the esophagus, the insertion rod is pulled out, causing deflection of the esophagus as the tube returns to its original pre-curved shape. A nonlinear constitutive equation of the Mooney–Rivlin type was used to describe the mechanical response of the tube material (ethylene vinyl acetate), with material parameters determined experimentally through uniaxial tensile testing. An analytical expression based on nonlinear elasticity theory is derived for the relationship between moment and curvature and used to evaluate the moments required to straighten the initially curved tube. The force vs. deflection relation was determined experimentally in a setup designed to model the straightening of the pre-curved tube. A finite element model was also developed to evaluate displacements and stresses in both the pre-curved and the straightened tube, allowing qualitative comparison of analytical, numerical and experimental results.