Comparison of a Miniaturized Implantable Two-Stage Rotodynamic Blood Pump to Equivalent Single-Stage Concepts

Hemocompatibility-related adverse events still limit the broader adoption of rotodynamic blood pumps. This study aims to evaluate the potential of a multistage pump design to enhance hemocompatibility in left ventricular assist devices.

Computational fluid dynamic simulations were utilized to compare the pump performance and hemocompatibility of a Two-Stage Pump to two equivalent single-stage devices, designed for identical operating conditions. One single-stage design features equal impeller and volute dimensions; the other, equal specific speed and specific diameter. Our simulation setup was validated against in vitro experiments of the pump performance of the Two-Stage Pump.

The Two-Stage Pump achieved a substantial reduction in circumferential velocity (24% and 29% reduction). Although the two-stage configuration thereby effectively reduces shear stress, it simultaneously translates to a longer residence time due to the larger priming volume. However, because the numerical blood damage estimation weighs shear stress exponentially more than residence time, the beneficial effect of reduced shear stress partially compensates for the longer residence time. As a result, the Two-Stage Pump demonstrates a lower hemolysis index (12% and 14% reduction) compared to both single-stage designs.

Our comparative study demonstrates that the two-stage concept offers favorable hemolysis measures compared to single-stage designs, as the reduction in peak shear stresses outweighs the disadvantage associated with prolonged residence time.