Improved Performance of the PIZZA Valve through Variation of Leaflet Overlapping

Objectives: The PIZZA valve (patent number DE 10 2008 012 438 B4) is a novel construction principle for a polymeric heart valve prosthesis. It consists of a foldable metal basis incorporating 8 metal loops acting as folding joints and restrictors for the movement of 8 triangular silicone leaflets. Ongoing development of this prototype led to a restrictor repositioning (PIZZA 2.0) and recently identified the shift from a planar to a cone shaped design (so-called TIPI 2.0) to increase performance. Here we present another approach, consisting of an increase in leaflet width leading to an overlap of the triangular leaflets (PIZZA 2.1). Furthermore, a hybrid prototype with overlapping leaflets in a cone shaped design (TIPI 2.1) was included in comparative experiments.

Methods: Prototypes were constructed from metal wire, silicone sheets and silicone rubber and tested in a HKP 2.0 pulse duplicator simulating 70 bpm and 70 mL stroke volume (cardiac output 4.9 L/min). Closing time and volume, leakage, regurgitation fraction, cardiac output and systolic pressure gradient were detected and compared between the prototypes. Valve opening cycles were visualized using a Casio EX-FH20 high speed camera and used to evaluate and improve the basic design.

Results: The comparison of the PIZZA 2.1 with the PIZZA 2.0 prototype demonstrated significant (p < 0.001) improvements in all recorded performance characteristics with reductions in mean systolic pressure gradient (−22.71%), leakage (−51.44%) and regurgitation fraction (−49.06%) resulting in an increased cardiac output (+140.67%). Comparison with the TIPI 2.0 underlined an improved closure of PIZZA 2.1, while the cone shaped prototype presented even lower systolic pressure gradients. The performance of the hybrid TIPI 2.1 fell short of the other two approaches, thus recommending the two development lines to remain separated.

Conclusions: The development of non-biological heart valve prostheses suitable for transcatheter implantation is of high interest due to the remaining problem of valve degeneration in commonly used bioprostheses. The presented prototype with overlapping leaflets represents a further step in the optimization of the new PIZZA valve construction principle using flexible elements, which may allow for a markedly reduced extent of the necessary lifelong anticoagulation compared to solid mechanical heart valves.

Keywords: mechanical valve; biological valve; transcatheter valve implantation

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