Comparison of the closing dynamic of mechanical prosthetic heart valves

To compare the closing dynamics of mechanical tilting disk prosthetic heart valves (OmniScience 225 [OS25], Medtronic-Hall 25 [MH25], Bjork-Shiley Monostrut 29 [BS29]) and bileaflet valves (CarboMedics 29 [CM29]) in the mitral position, an x-ray high speed video camera (XHVC) and a mechanical mock circulator were used. From the continuous images taken with the XHVC, the starting point of closing and the period during closing (PDC) were measured. Pressures and flow rate were recorded at 500 Hz synchronously with the XHVC. A pressure difference across the valves at the onset of closing (dp(c)) was newly introduced to compare the closing response. Using 60 and 100 bpm, the following results were obtained: 1) the CM29 had less PDC and maximum backflow rate than the BS29; 2) the dp(c) and the PDC at 100 bpm were larger than those at 60 bpm; 3) the dp(c) of the MH25 was the lowest; and 4) the PDC of the CM 29 was the shortest. With regard to the effect of valve design on closing dynamics, it was shown that: 1) less momentum of inertia of the occluder and disk traveling angle resulted in lower dp(c) and shorter PDC, and 2) the higher the dp(c) and the PDC became, the larger the maximum back-flow rate that was generated, and 3) low final closing speed will be achieved for small disk travelling angle.