Further Evolution of a New Nonbiological Transcatheter Valvular Prosthesis

Objectives: Current mechanical heart valves are constructed with solid elements thus being not suitable for transcatheter based implantation. Furthermore, the moving solid elements as well as flow dynamics promote chronic hypercoagulation resulting in the need for lifelong anticoagulation. Biological valves, in contrast can be folded but degenerate after several years. To overcome these obstacles a new type of artificial heart valve constructed from flexible elements was developed and patented (DE 10 2008 012 438 B4). We report on the opening and closure characteristics of this valve design as well as the optimization process to further reduce regurgitation and improve hemodynamics.

Methods: Prototypes were constructed from metal wire and silicone sheets and tested in a pulse duplicator at 70 bpm and 70 ml stroke volume (cardiac output 4.9l/min). Mean transvalvular pressure gradients (mTVG; mm Hg) and regurgitation volume (RV; mmHg) were detected and compared with standard bioprostheses. Valve opening cycles were visualized using a Casio EX-FH20 high speed camera and used to evaluate and improve the basic design.

Results: The prototype can be folded for transcatheter implantation and demonstrates promising performance characteristics similar to standard pericardial bioprostheses. Hemodynamic characteristics were improved by switching from a planar (PD) to a cone shaped design (CD) reducing the size of metal structures in the opening volume which are required to maintain valve function (mTVG: PD: 10.2 mm Hg; CD: 8.5 mm Hg; RV: PD: 5.2 ml; CD: 4.8 ml).

Conclusion: The development of a mechanical heart valve suitable for transcatheter implantation is of high interest as an alternative for commonly used bioprostheses as they do not degenerate. Furthermore, a construction utilizing flexible elements and optimized flow characteristics may allow for a markedly reduced extent of the necessary lifelong anticoagulation.