Assessment of a Re-Engineered 3-D Printable Poppet Heart Valve

The explanation of Cape Town poppet valves 30+ years after implantation in pristine condition prompted this re-engineering project. Modern hydrodynamic principles and computational fluid dynamics (CFD) were used to design a valve using a 3-D printable titanium frame and a silastic poppet.

After CFD assessment of the design, the assembled prototypes were tested in a Vivitro pulse duplicator. Flow dynamics and shear stresses were evaluated by particle imaging velocimetry (PIV). Results were compared to those obtained in a similar sized bi-leaflet valve.

6 prototypes were manufactured from a single block of stainless steel and implanted in the right ventricle outflow tract without any anti coagulation in an ovine model for 180 days. None of the valves clotted and no thrombo-embolic event could be demonstrated.

The CAD design was finalized and Ti - 6Al4V (ELI) heart valve frames were produced via DMLS on a EOSINT M280 system. Specimens (n=6) were tested in the as-built state. Failure was induced for quality and feasibility purposes. Mean failure load was 162N (range 116 – 217N) before polishing and heat treatment.

Surfaces after 3-D printing are rough and presents a challenge both as sites of cracks and initiation of platelet adhesion and clotting. Polishing and heat treatment will thus add additional strength to the frame.

The reengineered poppet valve has excellent hemodynamics and exceeds FDA requirements. Shear stress induced platelet activation remains below activation levels as demonstrated in CFD and PIV studies. Manufacturing by 3-D printing is possible and strength requirements were satisfied. This methodology would allow mass production of a low cost mechanical valve.