Effects of blood pump orientation on performance: In vitro assessment of universal advanced ventricular assist device

An advanced ventricular assist device (VAD), which is under development in our institution, has specific features that allow changes in the axial rotor position and pump performance by intrapump pressure difference. However, performance could be influenced by the pump orientation because of the effect of gravity on the rotor position. The purpose of this study was to evaluate the effects of pump orientation on the pump performance, including pulse pressure and regurgitant flow through the pump when the pump was stopped. Bench testing of the VAD was performed on a static or pulsatile mock loop with a pneumatic device to simulate the native ventricle. The pump performance, including pressure-flow curve, pulsatility, and regurgitant flow, was evaluated at several angles, ranging from -90° (inlet pointed upward) to +90° (inlet pointed downward) at pump speeds of 2000, 2500, 3000, and 3500 rpm. The pump performance was slightly lower at +90° at all rotational speeds, compared with -90°. The pulse pressure on the pulsatile mock loop (80 bpm) was 50 mm Hg without pump support, remained at 50 mm Hg during pump support, and was not changed by orientation (-90°, 0°, and +90°). When the pump was stopped, the regurgitant flow was near 0 L/min at all angles. Pump orientation had a minor effect on pump performance, with no effect on pulse pressure or regurgitant flow when the pump was stopped. This indicates that the effect of gravity on the rotor assembly is insignificant.