Effects of Leaflet Design on Structural Integrity and Pump Efficiency of Heart Valves

Heart valve disease results in inadequate blood supply from the heart to the body and could cause many complications, including heart attack, stroke, blood clots, heart arrhythmia, or even sudden death. Conventional heart valve treatments often involve risky and lengthy procedure that requires thoracotomy (open chest). In recent years, interventional transcatheter heart valve products have been launched on the market and becomes popular. The procedure includes deploying a transcatheter heart valve to the lesion site through a micro-catheter to restore normal blood flow.<br/><br/>This study proposed a novel design methodology for transcatheter heart valve leaflets. Unlike most transcatheter heart valves today, our heart valve designs deviated from conventional 3-D molding techniques and used 2-D quadrics sketches instead to save manufacturing cost. Polytetrafluoroethylene (e-PTFE) and e-PTFE with the addition of Polyethylene Terephthalate (e-PTFE + PET) were employed as the leaflet materials due to their high blood biocompatibility. The heart valve has to maintain appropriate valve orifice area during opening and ensure secured seal when closed. In addition, it is essential to withstand large dimensional changes and significant deformations during crimping (inside catheter) and deployment (to heart chamber). An interventional transcatheter heart valve was integrated by combining a nitinol scaffold with an expanded e-PTFE leaflet.<br/><br/>A series of tasks including design, computer simulation, laser cutting and its associated heat treatment, and bench testing were conducted. Ten leaflet designs were sketched using 2-D quadrics and cut from e-PTFE fabrics. Finite Element models were developed to facilitate the design iterations and evaluate the heart valve structural integrity from the crimping into a catheter to the deployment inside the heart chamber for both leaflet and nitinol scaffold. Computational Fluid Dynamics were also analyzed to evaluate the pump efficiency of the heart valve pre vs. post replacement. Laser cutting, heat treatment, electro-polishing, and bench testing were implemented to manufacture and test the prototypes for the proof of concept. Results showed that the leaflet design affected the pump efficiency of the heart valve and the 2-D quadrics leaflet designs were able to provide good performance with reduced cost.