Nonthrombogenic Modification of Blood-Contacting Surfaces of Ventricular Assist Devices

Summary

We have developed a pneumatic ventricular assist device (VAD) for temporary right, left, or bi-ventricular assist. The blood pump consists of a soft housing, diaphragm, tricuspid outflow valve, and bi-flap inflow valve. All components, except for the bi-flap valve were made by the vacuum-forming technique from a polyurethane (Pellethane; Dow Chemical Japan, Tokyo, Japan). Our previous studies demonstrated that the pump showed excellent hemodynamic characteristics; however, the blood compatibility of the blood pump still remains as a major problem for longer-term application of more than 1 month. In this study, we applied a novel surface modification technique to improve the blood compatibility of the blood pump. The technique involved heparin immobilization, using ozone oxidation. The blood-contacting surfaces of the pump, including the valves, were first treated with ozone gas, followed by the surface grafting of poly(ethylene imine) (PEI), after which heparin was coupled to the PEI spacer. This technology has significant advantages in the application to artificial organs of a complex design. These surface modified blood pumps were evaluated in vitro, using an epifluorescent video microscope (EVM) in combination with a parallel plate flow chamber, and in vivo in a chronic sheep LVAD model. The preliminary results (<3 months) demonstrated that these modified surfaces showed improved blood compatibility over the control Pellethane surfaces. Longer-term evaluations (>3 months) are currently underway.