In Vitro Hydrodynamic Analysis of Pin and Cone Bearing Designs of the Jarvik 2000 Adult Ventricular Assist Device

Abstract

The Jarvik 2000 adult ventricular assist device (VAD) is a second-generation blood pump with mechanical contact bearings. The original configuration of the pump employed a pin bearing and a more recent configuration uses a cone bearing. We compare the hydrodynamic performance of the two designs under steady-state and pulsatile flow conditions in vitro. Furthermore, we employ the Intermittent Low Speed (ILS) Flowmaker Controller to demonstrate the effect on pulsatility index (PI) performance of both device configurations. We use an open-loop flow system in both steady-state and pulsatile arrangements, complete with pressure transducers and flow probes. Working fluid was a 3.6 cP blood-analog, glycerin-water solution. Steady-state flow tests were carried out to determine pressure-flow (H-Q) performance curves. Pulsatile tests under normotensive, hypertensive, and hypotensive conditions were executed with controller speed 3 (10710 ± 250 rpm) at 100 beats per minute. Steady-state tests show greater capacity for pressure and flow with the cone bearing, compared with pin bearing, with best efficiency point (BEP) 68% greater for cone bearing. Pulsatile tests show the cone bearing design to yield a 20% increase in Qavg , a 17% decrease in pulsatility index (PIQ ), and a qualitative increase in pressure responsivity. The ILS mode (for both bearing designs) decreases Qavg by 68% and likewise increases PIQ by 360% and pulsatility ratio (Rpul ) by 200%. The ILS controller regularly reduces the flow, increasing pulsatility index during device operation. The Jarvik 2000 continuous-flow VAD can sustain pulsatile flow under pulsating pressure conditions. The new cone bearing design yields increased flow rates over the earlier pin bearing design.