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A proper interpretation of the forces developed during stent crimping and deployment is of paramount importance for a better understanding of the requirements for successful heart valve replacement. The present study combines experimental and computational methods to assess the performance of a nitinol stent for tissue-engineered heart valve implantation. To validate the stent model, the mechanical response to parallel plate compression and radial crimping was evaluated experimentally. Finite element simulations showed good agreement with the experimental findings. The computational models were further used to determine the hoop force on the stent and radial force on a rigid tool during crimping and self-expansion. In addition, stent deployment against ovine and human pulmonary arteries was simulated to determine the hoop force on the stent-artery system and the equilibrium diameter for different degrees of oversizing.

A proper interpretation of the forces developed during stent crimping and deployment is of paramount importance for a better understanding of the requirements for successful heart valve replacement. The present study combines experimental and computational methods to assess the performance of a nitinol stent for tissue-engineered heart valve implantation. To validate the stent model, the mechanical response to parallel plate compression and radial crimping was evaluated experimentally. Finite element simulations showed good agreement with the experimental findings. The computational models were further used to determine the hoop force on the stent and radial force on a rigid tool during crimping and self-expansion. In addition, stent deployment against ovine and human pulmonary arteries was simulated to determine the hoop force on the stent-artery system and the equilibrium diameter for different degrees of oversizing.

Purpose This study was designed to evaluate performance and tissue response to a self-expandable bioabsorbable vein stent-base cut from a tube with enhanced stiffness and strength in vitro and in vivo. Methods A diamond-shaped stent-base was cut from a sequential biaxially strained poly(L-lactide) (PLLA) tube for optimized performance. The performance of the stent-base was evaluated in a finite element analysis model, and validation was attempted in vitro through a cyclic flat-plate compression and radial force measurement. The performance of the stent-base was tested in vivo using 3 sheep with 2 implants each for 2 and 3½ weeks, respectively. Results In vitro the stent-base showed an elliptical deformation but no fractures. In vivo the stent-base showed adequate radial force and no migration. All implanted stent-bases showed multiple fractures not only at the predicted stress zones but at all connecting points. Fragments of the caudal stent-base stayed in the vein wall indicating sufficient tissue coverage to avoid embolization of the fractured stent pieces, whereas fragments from the cranial device remaining were few. Neointima formation was confirmed histologically at 2 and 3½ weeks. Conclusion A bioabsorbable self-expandable stent-base made from PLLA for large veins seems feasible, but over time, the PLLA used in this study appears too stiff and lacks the sufficient flexibility to move with the vena cava, causing multiple fractures.