Fluid dynamic optimization of a ventricular assist device using particle image velocimetry

Thrombus formation and resulting thromboembolism are major risks that can i mpede the widespread use of ventricular assist devices (VADs). Adverse flow patterns (turbulence and stasis) have been implicated in thrombogenesis. T his study focuses on optimization of VAD geometry, port orientation, and fl uid dynamics to reduce thrombus formation. Particle image velocimetry with cross-correlation was performed using Amberlite particles suspended in dist illed water. The transparent VADs were illuminated by halogen lamps. Four d ifferent VADs were tested in an iterative approach toward optimization. A p eak shear stress of 9,100 dynes/cm(2) was noted in the first configuration immediately after the end of systole at the outlet port. Modifications in c hamber geometry, port diameters and orientation, and valve enclosure design yielded shear stresses in the two subsequent geometries of 5,100 dynes/cm( 2) and 1,900 dynes/cm(2), respectively. For the third iteration, a region o f stasis occurred during the transition between the inlet port and the bloo d chamber. Further modifications were implemented, including a reduction in port diameters and further smoothing of the port entry region. This elimin ated stasis and yielded a maximum shear level of 4,100 dynes/cm(2). In conc lusion, optimization was achieved through geometric modification of the VAD , thus minimizing adverse flow conditions.