Closing behavior of a new bileaflet mechanical heart valve

Recently, the in vivo cavitation potential has become a primary concern among manufacturers of new mechanical heart valves (MHV). An experimental/computational program was designed to investigate each of the flow parameters involved. It was established that the closing velocity of the leaflet holds the key to MHV cavitation. One of the novel concepts of the new bileaflet mechanical heart valve (1205-MHV) was its ability to operate with a relatively small angular excursion that led to a much smaller closure velocity at impact (as compared with control valves). This is believed to significantly reduce the cavitation potential. The 1205-MHV is characterized by a longer valve body, with the hinges protruding further upstream. The unique design allows the valve the freedom to open as much as 90 degrees. The closure velocities are reduced by a smaller leaflet excursion (50 degrees), combined with a floating hinge that allows absorption of part of the impact energy at closure. The impact velocities of the 1205-MHV leaflets at closure were measured by a laser sweeping technique that monitored the leaflet closing motion with a precision of 5 μsec within the last 3 degrees before impact. The 27 mm 1205-MHV (the largest size) was tested in the program by mounting the valve in the mitral position of a physiologic mock circulatory loop. The valve was tested at 70, 90, and 120 bpm. The results were compared with those of a St. Jude Medical 29 mm MHV. The closure velocities measured with the 1205-MHV were significantly lower than those measured with the control valve. The leaflet bouncing phenomenon characteristic of the control valve at various heart rates was found to occur only at a 120 bpm heart rate for the 1205-MHV.