Reconstruction of Closing Phase Kinematics by Motion Analysis for a Prosthetic Bileaflet Valve

Abstract

The occluder motion of bileaflet valves has been studied by researchers in order to understand critical kinematic features that can be associated with post-implant complications. The closing phase, in particular, was studied monodimensionally using different techniques (laser and timing gate) in order to investigate the cavitation potential of valves, but the results these techniques yield are not measurable in vivo. Therefore we analysed the valve closing phase motion by means of High Speed Videography (HSV) on a bileaflet valve model, the 29 mm-sized Sorin Bicarbon. Testing was performed in a standard way using the pulse duplicator developed at the University of Sheffield (UK) with the valve mounted in mitral position, and the HSV system (Kodak Ektapro) running at 12000 frame per sec, synchronised on the flow waveform. The kinematic analysis of this prosthesis started from a modelling process needed to reduce the leaflet degrees of freedom due to the pivot design. In fact, the spherical coupling between leaflet and housing yields hypocycloid trajectories for the leaflet points. Thus a trajectory table (TT) was built that can be addressed by the^ coordinate of the recorded leaflet points, reducing the problem to a monodimensional one. To verify the model we used a two-orthogonal-camera set up, at 1000 frame per/sec. Finally, from the frontal view recordings at 12000 Hz and the trajectory table (TT), the whole leaflet motion just immediately before the closure time was obtained synchronously with pressure and flow traces. Motion analysis calculations provided angular and tip velocities related to the left ventricular dp/dt values to evaluate the prosthesis function and performance.