Structural analysis of implantable biomedical heart assist device fixation

Abstract

This thesis presents how experimentation, numerical simulation, optimization, and mathematical analysis, can be applied to study and improve the fixation of left-ventricle leads within a cardiac vein. Left-ventricle cardiac leads for implantable pacemakers can lose fixation within a cardiac vein and dislodge. A common lead-fixation mechanism for left-ventricle leads was investigated that used a two- or three-dimensional shape at the distal end. The lead and the distal end are constructed from a metal coil that is pre-formed into a two- or three-dimensional shape. Analytical beam approximations of a coil were developed to determine how coil stiffness is affected by coil geometry and material. In-vitro experimentation with a radial force tester was used to measure the overall force between a two- or three-dimensional distal shape within a straight cylindrical tube. Data processing techniques using a moving average were applied to interpret the force data. Numerical simulation using a beam approximation for the coil determined the overall force between a distal shape and a straight cylindrical tube. The distribution of force along the distal shape, including tip force was also obtained from the simulation. The simulation models were validated with experimental data. Using numerical simulation, the model of the distal shape was changed to a spiral shape and then optimized. Since actual cardiac veins are curved, the simulation model was updated with a curved tube to determine how the distal shapes would perform. A mathematical analysis using engineering principles was also applied to obtain a simple analytical equation relating a deformed distal shape to force.