Effects of Pulse Duplicator Designs on Valve Behavior
Caroline C. Smid1, Georgios Pappas1, Volkmar Falk2, Nikola Cesarovic3, Paolo Ermanni1.
1CMASLab ETH Zurich, Zurich, Switzerland, 2Klinik für Herz-, Thorax- und Gefäßchirurgie Ärztlicher, Deutsches Herzzentrum Berlin, Berlin, Germany, 3Translational Cardiovascular Technologies, ETH Zürich, Zurich, Switzerland.
BACKGROUND: Despite decades of research, it remains challenging for artificial heart valves to match hemodynamic and durability parameters of their native counterparts. A potential approach to address these challenges during valve design and development process is an in-vitro assessment of the hemodynamic performance. For this purpose, the use of high-fidelity pulse duplicators is necessary. Although nowadays such devices are commercially available, the high cost often renders them unattainable for academic research. Moreover, such systems are usually prohibitive to any adaptations, usually necessary for laboratory investigations. Here we present a custom-made high-fidelity pulse duplicator for comprehensive hemodynamic assessment of novel aortic valve implants.
METHODS: For the hydrodynamic assessment a custom-made pulse duplicator that simulates the left side of the heart consisting of pulsatile piston-pump, inlet (mitral) and outlet (aortic) valves, as well as tubing and compliance chamber, has been developed according to the requirements of ISO 5840 Standard. A synchronous data acquisition of the pressure readings before and after the aortic valve, high-speed camera, and pulsatile piston pump is managed via MATLAB. The obtained raw pressure data (250 Hz) of a commercially available bioprosthetic heart valve, namely the ventricular and aortic pressure, were validated with those of a healthy pig (500 Hz with 100Hz low-pass filter). The motion (kinematics) of the valve leaflets was video-tracked with 250 frames per second and the orifice area was calculated.
RESULTS: With the aid of a customized post-processing code, the unfiltered high-fidelity pressure data and the geometric orifice area can be plotted over time. Furthermore, not only the mean pressure gradient is calculated, but also the valve opening pressures. By tracking the position of the piston pump, the start of systole and diastole can be determined, as well as the flow velocity, and the inertial force. Various versions of the pulse duplicator showed that the pressure curves are very sensitive to small adjustments to the setup.
CONCLUSIONS: Results of this study validate the new concept of the custom-made high-fidelity pulse duplicator setup as a suitable characterization tool of the aortic valve hemodynamics and kinematics with highly accurate and reproducible results. 
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