Hydrodynamic characteristics of the Edwards MIRA bileaflet valve in a pneumatic ventricular assist device.

In the present study, we used a bileaflet valve in our pneumatic ventricular assist device (PVAD). To estimate the effects of the orientation angle of a bileaflet valve on mechanical heart valve cavitation in the PVAD, the valve was rotated from 0 degrees to 90 degrees on an inclined horizontal plane. Tests were conducted under physiological pressure with heart rates of 80 bpm and a systolic ratio of 43%. A 23-mm Edwards MIRA bileaflet valve was installed in the inlet position of the PVAD, and the valve-closing velocity was measured with a closed circuit digital laser displacement sensor. Images of mechanical heart valve cavitation bubbles were recorded with the use of a high-speed video camera. The closing delay time between the two leaflets ranged from 0.88 +/- 0.41 to 0.50 +/- 0.27 ms, which was the largest at a valve orientation angle of 0 degrees . Cavitation bubbles were concentrated along the leaflet tip and were caused by the initial valve closure, valve rebound, and the second valve closure. Even when the valve-closing velocity was slow, stronger cavitation bubbles were observed at the second valve closure and valve rebound. The cavitation event ratio differed from the valve orientation angle, which resulted from the high initial valve closure.